Application of Naphthylindole-Derived Phosphines as Organocatalysts

School of Chemistry and Materials Science, Jiangsu Normal University , Xuzhou , 221116 , China. J. Org. Chem. ... Publication Date (Web): August 14, 2...
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Cite This: J. Org. Chem. 2018, 83, 10060−10069

Application of Naphthylindole-Derived Phosphines as Organocatalysts in [4 + 1] Cyclizations of o‑Quinone Methides with Morita−Baylis−Hillman Carbonates Fei Jiang, Gui-Zhen Luo, Zi-Qi Zhu, Cong-Shuai Wang, Guang-Jian Mei, and Feng Shi* School of Chemistry and Materials Science, Jiangsu Normal University, Xuzhou, 221116, China

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S Supporting Information *

ABSTRACT: An organocatalytic [4 + 1] cyclization of o-QMs with MBH carbonates has been established using naphthylindole-derived phosphine (NIP) as an organocatalyst. By using this approach, a series of 2,3-dihydrobenzofuran derivatives have been synthesized in high yields and excellent diastereoselectivities (up to 99% yield, >95:5 dr). This reaction not only has established the first [4 + 1] cyclization of o-QMs with MBH carbonates but also represents the first application of naphthylindole-derived phosphines as organocatalysts in catalytic reactions. In addition, this reaction has also provided a useful method for constructing 2,3-dihydrobenzofuran scaffolds.

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INTRODUCTION In recent years, o-quinone methides (o-QMs)1−3 have emerged as a class of versatile building blocks in [4 + n] cyclizations,4−7 which offer an efficient method for the construction of oxygencontaining heterocyclic frameworks (Scheme 1). However,

Despite these elegant approaches, [4 + 1] cyclizations of oQMs with one-carbon synthons are still rather limited, which requires the selection of suitable one-carbon synthons and the specific design of [4 + 1] cyclizations of o-QMs. In this context, Morita−Baylis−Hillman (MBH) carbonates greatly aroused our interest because this type of reactant can act as one-carbon synthons in cyclizations,15 which have been promoted by phosphine catalysts such as PPh3, PBu3, and chiral phosphines.16 In our previous work, we established the construction of a new class of naphthylindole skeleton and synthesized a naphthylindole-derived phosphine (NIP),17 which might be used as an organocatalyst in phosphinepromoted reactions. To develop [4 + 1] cyclizations of o-QMs and to discover the application of this class of naphthylindolederived phosphines as organocatalysts, we selected MBH carbonates as one-carbon synthons and designed a [4 + 1] cyclization of o-QMs with MBH carbonates under the catalysis from naphthylindole-derived phosphines. Herein we report an organocatalytic [4 + 1] cyclization of oQMs with MBH carbonates using naphthylindole-derived phosphine as an organocatalyst. By using this approach, a series of 2,3-dihydrobenzofuran derivatives have been synthesized in high yields and excellent diastereoselectivities (up to 99% yield, >95:5 dr). This reaction has not only established the first [4 + 1] cyclization of o-QMs with MBH carbonates but also represents the first application of naphthylindole-derived phosphines as organocatalysts in catalytic reactions. In

Scheme 1. Profile of o-QM-Involved Cyclizations

most of the cyclizations are focused on [4 + 2] cyclizations of o-QMs with electron-rich alkenes,4−6 leading to the construction of chroman skeletons (eq 1). On the contrary, [4 + 1] cyclizations of o-QMs with one-carbon synthons are underdeveloped, which nevertheless would provide an easy access to 2,3-dihydrobenzofuran scaffold (eq 2). A survey of the literature only revealed several examples of [4 + 1] cyclizations of o-QMs with one-carbon synthons (Scheme 2).8−14 In these cases, sulfur ylides (eq 3),8 pyridinium methylides (eq 4),9 in situ generated oxyphosphonium enolates (eq 5), 10 aldehydes (eq 6), 11 ammonium ylides (eq 7),12 and bromomalonates13 or 3chlorooxindoles14 (eq 8) were successfully utilized as onecarbon synthons to perform [4 + 1] cyclizations with o-QMs. © 2018 American Chemical Society

Received: June 3, 2018 Published: August 14, 2018 10060

DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

Article

The Journal of Organic Chemistry Scheme 2. Limited Examples of [4 + 1] Cyclizations of o-QMs

dihydrobenzofuran products 3 in generally high yields (52%− 99%) and excellent diastereoselectivities (83:17 to >95:5 dr). In detail, a variety of phenyl groups bearing ortho- (entries 2− 5), meta- (entries 6−8), para-substituents (entries 9−12) could serve as suitable R groups for o-QMs 1. In addition, either electron-donating or electron-withdrawing phenyl groups could be utilized as competent R substituents. In most cases, it seemed that the electronic nature of the phenyl groups imposed some effect on the yield of the reaction. For example, o-QMs 1d,e bearing electron-withdrawing groups (F, Cl) delivered products 3da−3ea in higher yields than their counterparts 1b,c bearing electron-donating groups (Me, MeO). Notably, o-QM 1m bearing a 2-thienyl group could also successfully participate in the [4 + 1] cyclization to afford product 3ma in a quantitative yield of 99% and an excellent diastereoselectivity of >95:5 dr (entry 13). Next, the applicability o-QMs 1 in [4 + 1] cyclizations with MBH carbonate 2b was studied (Table 3). Obviously, a variety of o-QMs 1 with different R substituents could smoothly react with MBH carbonate 2b under the standard conditions, which generated [4 + 1] cyclization products 3 in uniformly excellent diastereoselectivities (all >95:5 dr) and moderate to excellent yields (40% to 95%). Similarly to the reactions with 2a, o-QMs 1 bearing either electronically neutral, rich, or poor phenyl groups could take part in the [4 + 1] cyclizations with 2b. However, in these cases, the electronic nature of the phenyl groups had a delicate effect on the yield of the reaction. It seemed that the position of the substituents on the phenyl ring had no significant impact on the reactivity. For instance, oQMs 1b, 1f, and 1i bearing o-, m-, and p-methyl-substituted phenyl groups underwent the [4 + 1] cyclization with 2b in similarly high yields (80%−93%, entries 2, 5, 7). Apart from oQMs 1a−1l with phenyl R groups (entries 1−10), o-QM 1m with a 2-thienyl group still proved to be a competent substrate, which performed [4 + 1] cyclization with 2b in a high yield of 81% and a high diastereoselectivity of >95:5 dr (entry 11). In addition to MBH carbonates 2a and 2b, substrate 2c could act as a suitable reaction partner to carry out [4 + 1] cyclization with o-QM 1a, which gave rise to 2,3dihydrobenzofuran product 3ac in a good yield of 77% and an excellent diastereoselectivity of >95:5 dr (Scheme 3).

addition, this reaction has also provided a useful method for constructing 2,3-dihydrobenzofuran scaffolds.

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RESULTS AND DISCUSSION Initially, the reaction of o-QM 1a with MBH carbonate 2a in the presence of naphthylindole-derived phosphine 4a was employed as a model reaction to test our hypothesis (Table 1, entry 1). Gratifyingly, the [4 + 1] cyclization of 1a and 2a in dichloromethane (DCM) smoothly occurred to afford 2,3dihydrobenzofuran product 3aa in a moderate yield of 56%, which indicated that our designed [4 + 1] cyclization is feasible and that the naphthylindole-derived phosphine catalyst can be applied to this cyclization. To further improve the yield of the [4 + 1] cyclization and to examine the catalytic activity of different naphthylindole-derived phosphines, we synthesized a series of phosphine catalysts 4 and evaluated their performance in catalyzing the reaction (entries 2−11). However, the results revealed that these phosphine catalysts 4b−k were inferior to catalyst 4a in terms of the yield (entries 2−11 vs 1). Then, in the presence of the optimal catalyst 4a, representative solvents were screened (entries 12−16), which discovered that no other solvents were superior to dichloromethane with regard to the yield (entries 12−16 vs 1). It was found that elevating the reaction temperature could improve yield to some extent (entries 17 and 18 vs 1), and 35 °C was selected as a suitable reaction temperature because it can give product 3aa in a higher yield of 70% (entry 17). Finally, modulating the reagent ratio (entries 19−23) revealed that the highest yield of 92% could be achieved when the molar ratio of 1a:2a was 1:2 (entry 19). So, this condition was chosen as the optimal reaction conditions. It should be mentioned that only one diastereomer of 3aa was observed during the condition optimization. In addition, we also employed commonly used phosphines such as PPh3 as a catalyst in the reaction (entry 24). It was found that PPh3 could also catalyze the [4 + 1] cyclization in a good yield of 85%, which was somewhat inferior to that of catalyst 4a in terms of the yield (entry 24 vs 19). After establishing the optimal reaction conditions, we carried out an investigation on the substrate scope of o-QMs 1 in [4 + 1] cyclizations with MBH carbonate 2a. As shown in Table 2, this [4 + 1] cyclization could be applicable to a wide range of o-QMs 1 bearing various R substituents, which offered 2,310061

DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

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The Journal of Organic Chemistry

Table 2. Substrate Scope of o-QMs 1 in [4 + 1] Cyclizations with MBH Carbonate 2aa

Table 1. Screening of Catalysts and Optimization of Reaction Conditionsa

entry

cat.

solvent

T (°C)

1a:2a

yield (%)b

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

4a 4b 4c 4d 4e 4f 4g 4h 4i 4j 4k 4a 4a 4a 4a 4a 4a 4a 4a 4a 4a 4a 4a PPh3

DCM DCM DCM DCM DCM DCM DCM DCM DCM DCM DCM acetone THF EtOAc toluene MeCN DCM DCM DCM DCM DCM DCM DCM DCM

25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 35 50 35 35 35 35 35 35

1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:1.2 1:2 1:3 1.2:1 2:1 3:1 1:2

56 trace trace 21 22 31 37 14 trace 15 trace 11 28 10 20 24 70 67 92 91 65 69 54 85

entry

3

R (1)

drb

yield (%)c

1 2 3 4 5 6 7 8 9 10 11 12 13

3aa 3ba 3ca 3da 3ea 3fa 3ga 3ha 3ia 3ja 3ka 3la 3ma

Ph (1a) 2-MeC6H4 (1b) 2-MeOC6H4 (1c) 2-FC6H4 (1d) 2-ClC6H4 (1e) 3-MeC6H4 (1f) 3-MeOC6H4 (1g) 3-ClC6H4 (1h) 4-MeC6H4 (1i) 4-MeOC6H4 (1j) 4-FC6H4 (1k) 4-ClC6H4 (1l) 2-thienyl (1m)

>95:5 >95:5 >95:5 >95:5 83:17 >95:5 >95:5 83:17 >95:5 >95:5 >95:5 >95:5 >95:5

92 82 63 95 99 77 64 89 96 52 68 96 99

a

Unless indicated otherwise, the reaction was carried out at the 0.1 mmol scale catalyzed by 10 mol % 4a in DCM (1 mL) at 35 °C under argon atmosphere for 12 h, and the molar ratio of 1:2a was 1:2. bThe dr value was determined by 1H NMR. cIsolated yield.

Table 3. Application of o-QMs 1 in [4 + 1] Cyclizations with MBH Carbonate 2ba

a

Unless otherwise indicated, the reaction was carried out at the 0.1 mmol scale and catalyzed by 10 mol % 4 in a solvent (1 mL) under argon atmosphere for 12 h. bIsolated yield and only one diastereomer was observed in all cases.

entry

3

R (1)

drb

yield (%)c

1 2 3 4 5 6 7 8 9 10 11

3ab 3bb 3db 3eb 3fb 3hb 3ib 3jb 3kb 3lb 3mb

Ph (1a) 2-MeC6H4 (1b) 2-FC6H4 (1d) 2-ClC6H4 (1e) 3-MeC6H4 (1f) 3-ClC6H4 (1h) 4-MeC6H4 (1i) 4-MeOC6H4 (1j) 4-FC6H4 (1k) 4-ClC6H4 (1l) 2-thienyl (1m)

>95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5

94 93 77 83 90 95 80 40 42 81 81

a

Unless indicated otherwise, the reaction was carried out at the 0.1 mmol scale catalyzed by 10 mol % 4a in DCM (1 mL) at 35 °C under argon atmosphere for 12 h, and the molar ratio of 1:2b was 1:2. bThe dr value was determined by 1H NMR. cIsolated yield.

Moreover, we also tried using MBH carbonates 2d,e as substrates (Scheme 4), which were derived from substituted aldehydes such as p-nitrobenzaldehyde and alkyl aldehyde. It was found that MBH carbonate 2d derived from p-nitrobenzaldehyde smoothly participated in the [4 + 1] cyclization to afford product 3ad in a moderate yield of 55% and an excellent diastereoselectivity of >95:5 dr (eq 9). However, MBH carbonate 2e derived from alkyl aldehyde failed to take part in the [4 + 1] cyclization (eq 10). The structures of all products 3 were unambiguously assigned by 1H and 13C NMR, IR, and HR MS. Furthermore, the structure of product 3aa was confirmed by H−H COSY, HMQC, and HMBC. In addition, the relative configuration of product 3aa was assigned as cis by NOSY (see Supporting

Scheme 3. Using MBH Carbonate 2c as a Substrate

Information for details). So, the relative configurations of other products 3 were assigned as cis by analogy. On the basis of the experimental results, we suggested two possible reaction pathways for this [4 + 1] cyclization of o10062

DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

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The Journal of Organic Chemistry Scheme 4. Using MBH Carbonates 2d,e as Substrates

Scheme 5. Possible Reaction Pathways

this 1-mmol scale reaction proceeded with a maintained high yield of 91% and an excellent diastereoselectivity of >95:5 dr, which indicated that this [4 + 1] cyclization could be used for larger-scale synthesis of 2,3-dihydrobenzofuran products 3. Furthermore, we performed a preliminary derivation of product 3aa by DDQ oxidation, which provided dibenzofuran derivative 5 in a considerable yield of 61% (Scheme 7). On the basis of a similar procedure in natural product synthesis,19 we considered that this derivation was a cascade reaction, which involved a sequence of oxidation of 3aa into alcohol E, dehydration of E to form triene F, 6π-electrocyclization of triene E to give intermediate G, and subsequent DDQ oxidation of G to furnish aromatized product 5. Finally, to investigate the preliminary application of axially chiral naphthylindole-derived phosphines 4 in the [4 + 1] cyclizations, we separated the enantiomers of 4a−f by preparative HPLC and employed them as chiral organocatalysts in [4 + 1] cyclization of o-QM 1a with MBH carbonate 2a (Table 4). The screening of chiral phosphines (R)-4 in DCM at 35 °C (entries 1−6) revealed that (R)-4f and (R)-4d exhibited higher catalytic activity than others in terms of controlling the enantioselectivity (entries 3 and 4 vs entries 1 and 2, and 5 and 6). Because (R)-4d could catalyze the reaction in a higher yield than (R)-4f (entry 4 vs 3), subsequent condition optimizations were performed in the presence of (R)-4d. The evaluation of different solvents (entries 7−12 and 4) found that chloroform was superior to others in delivering the [4 + 1] cyclization with the highest

QMs 1 with MBH carbonates 2 (Scheme 5). In both of the two pathways, naphthylindole-derived phosphine 4a acted as an organocatalyst to activate MBH carbonates 2, resulting in the generation of allylic phosphorus ylide A. In the next step of nucleophilic addition of ylide A to o-QMs 1, there are two possible selectivity, namely, α-selectivity15d and γ-selectivity.18 In pathway a, ylide A attacked o-QMs 1 with a α-selectivity to give intermediate B, which rapidly underwent an intramolecular nucleophilic substitution to generate products 4. In pathway b, ylide A attacked o-QMs 1 with a γ-selectivity to form intermediate C, which could transform to intermediate D. Then the intramolecular nucleophilic addition of intermediate D afforded the final products 4. Between the two pathways, pathway b (γ-selectivity) is more possible because the γaddition of intermediate A to o-QMs 1 is more sterically favored.18 To demonstrate the utility of this [4 + 1] cyclization, a 1mmol scale synthesis of product 3aa was performed (Scheme 6). Compared with the small-scale reaction (Table 2, entry 1), Scheme 6. A 1-mmol Scale Synthesis of 3aa

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DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

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The Journal of Organic Chemistry Scheme 7. Preliminary Derivation of Product 3aa

diastereoselectivity (entry 14). Although the enantioselectivity of product 3aa was still at a low level, these results implied that this class of axially chiral naphthylindole-derived phosphines could be applied to the catalytic asymmetric [4 + 1] cyclizations and could control the enantioselectivity to some extent.

Table 4. Preliminary Application of Axially Chiral Phosphines 4 in Catalytic Asymmetric [4 + 1] Cyclizationsa

■ entry

(R)-4

solvent

T (°C)

yield (%)b

drc

ee (%)d

1 2 3 4 5 6 7 8 9 10 11 12 13 14

(R)-4a (R)-4b (R)-4c (R)-4d (R)-4e (R)-4f (R)-4d (R)-4d (R)-4d (R)-4d (R)-4d (R)-4d (R)-4d (R)-4d

DCM DCM DCM DCM DCM DCM acetone THF EtOAc toluene MeCN CHCl3 CHCl3 CHCl3

35 35 35 35 35 35 35 35 35 35 35 35 0 50

44 40 24 31 27 52 38 24 22 22 29 45 23 89

>95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 >95:5 95:5 >95:5 >95:5 >95:5

16 13 20 20 3 0 13 18 6 11 20 24 26 24

CONCLUSIONS In summary, we have established an organocatalytic [4 + 1] cyclization of o-QMs with MBH carbonates using naphthylindole-derived phosphine as an organocatalyst. By using this approach, a series of 2,3-dihydrobenzofuran derivatives have been synthesized in high yields and excellent diastereoselectivities (up to 99% yield, >95:5 dr). Furthermore, the preliminary application of axially chiral naphthylindole-derived phosphines in the catalytic asymmetric [4 + 1] cyclizations indicated that this class of axially chiral catalysts could be applied to such reactions and could control the enantioselectivity to some extent. This reaction not only has established the first [4 + 1] cyclization of o-QMs with MBH carbonates, but also represents the first application of naphthylindole-derived phosphines as organocatalysts in catalytic reactions. In addition, this reaction has also provided a useful method for constructing 2,3-dihydrobenzofuran scaffolds. So, this reaction will not only enrich the chemistry of o-QMs, especially o-QMinvolved cyclizations, but also open a new window for finding the application of naphthylindole-derived phosphines as organocatalysts.

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EXPERIMENTAL SECTION

1

H and 13C NMR spectra were measured at 400 and 100 MHz, respectively. The solvent used for NMR spectroscopy was CDCl3, using tetramethylsilane as the internal reference. HRMS (ESI) was determined by a HRMS/MS instrument. Analytical grade solvents for the column chromatography were used after distillation, and commercially available reagents were used as received. Catalysts 4 were prepared according to the procedures in the literature17 and the general synthetic route was illustrated in the Supporting Information. In the synthetic route, most of S3 (except for S3c) are known compounds which were prepared in our previous work.17 The characteristic data of S3c are as follows. 1 - ( 2 - ( B i s ( 3 - F l u o r o p h e n y l ) m e t h y l ) - 1 H - i n do l - 3 - y l ) naphthalen-2-ol (S3c). Flash column chromatography eluent, petroleum ether/ethyl acetate = 20/1; reaction time = 12 h; yield: 93% (4.3 g); colorless solid, mp 85.5−86.2 °C; 1H NMR (400 MHz, CDCl3) δ 8.25 (s, 1H), 7.86 (t, J = 8.0 Hz, 2H), 7.44 (d, J = 8.2 Hz, 1H), 7.40 (d, J = 8.3 Hz, 1H), 7.36−7.30 (m, 2H), 7.30−7.26 (m, 3H), 7.23−7.17 (m, 2H), 7.14−7.09 (m, 1H), 7.01−6.82 (m, 5H), 6.81−6.75 (m, 1H), 5.45 (s, 1H), 5.23 (s, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 163.1 (d, J = 246 Hz), 162.9 (d, J = 245 Hz), 152.3,

a

Unless indicated otherwise, the reaction was carried out at the 0.05 mmol scale catalyzed by 10 mol % (R)-4 in a solvent (0.5 mL) at T °C under argon atmosphere for 12 h, and the molar ratio of 1a:2a was 1:1.2. bIsolated yield. cThe dr value was determined by 1H NMR and HPLC. dThe ee value was determined by HPLC.

enantioselectivity of 24% ee (entry 12 vs entries 4 and 7−11). Then, in the best solvent of chloroform, we studied the effect of the reaction temperature on the reaction (entries 12−14). It was found that lowering the reaction temperature from 35 °C to 0 °C led to a sharp decrease of the yield albeit with a slightly improved enantioselectivity of 26% ee (entry 13 vs 12), while elevating the reaction temperature from 35 °C to 50 °C could greatly improve the yield to a high level of 89% with a retained enantioselectivity of 24% ee (entry 14 vs 12). So, under current condition, axially chiral naphthylindole-derived phosphine (R)4d could catalyze the [4 + 1] cyclization of o-QM 1a with MBH carbonate 2a in a high yield and an excellent 10064

DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

Article

The Journal of Organic Chemistry

(E)-Benzyl 2-(7-(2-Chlorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ea). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr = 83:17; yield: 99% (45.5 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.47−7.42 (m, 1H), 7.36−7.27 (m, 6H), 7.21−7.15 (m, 2H), 6.81 (d, J = 15.7 Hz, 1H), 6.58 (s, 1H), 6.46 (s, 1H), 6.40 (s, 1H), 6.30−6.18 (m, 1H), 5.94 (s, 1H), 5.90 (s, 2H), 5.36 (d, J = 6.3 Hz, 1H), 5.27−5.16 (m, 2H), 4.06−3.96 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.1, 153.6, 148.0, 142.0, 139.0, 135.4, 134.9, 132.9, 132.6, 129.6, 128.5, 128.2, 127.6, 126.9, 126.8, 126.1, 118.9, 105.3, 101.3, 93.09, 86.7, 66.8, 53.3; IR (KBr): 3678, 2977, 1744, 1479, 1277, 1152, 749 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H21ClO5Na 483.0976, found 483.0973. (E)-Benzyl 2-(7-(3-Methylstyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3fa). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 77% (33.9 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.31 (s, 5H), 7.21−7.15 (m, 1H), 7.15−7.00 (m, 3H), 6.56 (s, 1H), 6.44 (s, 1H), 6.36 (d, J = 16.4 Hz, 2H), 6.30−6.22 (m, 1H), 5.92 (s, 1H), 5.90 (d, J = 1.5 Hz, 2H), 5.32 (d, J = 6.1 Hz, 1H), 5.21 (s, 2H), 4.03−3.85 (m, 1H), 2.33 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 153.6, 147.9, 142.0, 139.1, 138.0, 136.6, 135.4, 131.5, 129.6, 128.5, 128.4, 128.3, 128.2, 127.0, 126.1, 123.6, 119.2, 105.3, 101.2, 93.0, 87.0, 66.7, 53.0, 21.3; IR (KBr): 3678, 2985, 2360, 1723, 1474, 1263, 748, 693 cm−1; HRMS (ESITOF) m/z: [M + Na]+ Calcd for C28H24O5Na 463.1522, found 463.1537. (E)-Benzyl 2-(7-(3-methoxystyryl)-6,7-dihydro-[1,3]dioxolo[4,5f ]benzofuran-6-yl)acrylate (3ga). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 64% (29.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.31 (s, 5H), 7.21 (t, J = 7.9 Hz, 1H), 6.90 (d, J = 7.7 Hz, 1H), 6.86−6.82 (m, 1H), 6.82−6.73 (m, 1H), 6.56 (s, 1H), 6.45 (S, 1H), 6.36 (d, J = 15.8 Hz, 2H), 6.31−6.22 (m, 1H), 5.92 (s, 1H), 5.91−5.87 (m, 2H), 5.32 (d, J = 6.0 Hz, 1H), 5.21 (s, 2H), 4.07−3.92 (m, 1H), 3.80 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 153.6, 147.9, 142.0, 139.1, 138.0, 136.6, 135.4, 131.5, 129.6, 128.5, 128.4, 128.3, 128.2, 127.0, 126.1, 123.6, 119.2, 105.3, 101.2, 93.0, 87.0, 66.7, 53.0, 21.3; IR (KBr): 3698, 2360, 1473, 1261, 1145, 1040, 751, 691 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C28H24O6Na 479.1471, found 479.1486. (E)-Benzyl 2-(7-(3-Chlorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ha). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr = 83:17; yield: 89% (40.9 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.31 (s, 5H), 7.28−7.27 (m, 1H), 7.22−7.17 (m, 2H), 7.17−7.12 (m, 1H), 6.54 (s, 1H), 6.47 (s, 1H), 6.39 (s, 1H), 6.33−6.23 (m, 2H), 5.94−5.92 (m, 1H), 5.92−5.88 (m, 2H), 5.32 (d, J = 5.7 Hz, 1H), 5.21 (d, J = 1.6 Hz, 2H), 3.98−3.85 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.1, 153.7, 148.0, 142.0, 139.0, 138.5, 135.3, 134.4, 131.5, 129.9, 129.7, 128.6, 128.5, 128.4, 128.3, 127.4, 126.3, 126.0, 124.6, 118.6, 105.3, 101.3, 93.1, 86.7, 66.8, 52.8; IR (KBr): 3496, 2360, 1473, 1261, 1145, 1040, 751, 691 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H21ClO5Na 483.0976, found 483.0979. (E)-Benzyl 2-(7-(4-Methylstyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ia). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 96% (42.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.31 (s, 5H), 7.20 (d, J = 8.1 Hz, 2H), 7.10 (d, J = 8.0 Hz, 2H), 6.57 (s, 1H), 6.45 (s, 1H), 6.35 (d, J = 17.9 Hz, 2H), 6.27−6.16 (m, 1H), 5.95−5.87 (m, 3H), 5.31 (d, J = 6.1 Hz, 1H), 5.21 (s, 2H), 4.03−3.85 (m, 1H), 2.33 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 153.6, 147.8, 141.9, 139.1, 137.3, 135.4, 133.9, 131.27, 129.2, 128.8, 128.5, 128.3, 126.3, 126.1, 119.3, 105.4, 101.2, 93.0, 87.1, 66.7, 52.9, 21.2; IR (KBr): 3696, 2979, 1745, 1476, 1278, 1154, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C28H24O5Na 463.1522, found 463.1523. (E)-Benzyl 2-(7-(4-Methoxystyryl)-6,7-dihydro-[1,3]dioxolo[4,5f ]benzofuran-6-yl)acrylate (3ja). Preparative thin layer chromatog-

143.5, 143.3, 138.1, 136.3, 134.2, 130.6 (d, J = 9 Hz), 130.1 (d, J = 8 Hz), 129.9, 129.0, 128.5, 128.1, 126.3, 125.5, 124.8, 124.3, 124.2, 123.2, 123.0, 120.8, 120.0, 117.0, 115.7, 115.5, 114.4 (d, J = 21 Hz), 114.1 (d, J = 21 Hz), 111.7, 111.2, 106.3, 47.9; IR (KBr): 3446, 3307, 1716, 1614, 1589, 1558, 1507, 1485, 1140, 961, 866, 780, 702, 695 cm−1; HRMS (ESI-TOF) m/z: [M − H]− Calcd for C31H20F2NO 460.1518, found 460.1522. General Procedure for the Synthesis of Products 3. Under argon atmosphere, to the mixture of phosphine catalyst 4a (0.01 mmol), o-QM 1 (0.1 mmol), and MBH carbonates 2 (0.2 mmol) was added dichloromethane (1 mL). After the reaction mixture was stirred at 35 °C for 12 h, the reaction was stopped, and the reaction mixture was purified through preparative thin layer chromatography to afford pure products 3. (E)-Benzyl 2-(7-Styryl-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran6-yl)acrylate (3aa). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 92% (39.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.44−7.27 (m, 9H), 7.26−7.16 (m, 1H), 6.58 (s, 1H), 6.48 (s, 1H), 6.40 (t, 2H), 6.29 (dd, J = 15.6 Hz, 1H), 5.94 (s, 1H), 5.91 (d, J = 1.6 Hz, 2H), 5.37 (t, J = 14.3 Hz, 1H), 5.21 (d, J = 12.3 Hz, 2H), 4.06−3.84 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 153.7, 147.9, 142.0, 139.1, 136.7, 135.4, 131.4, 129.8, 128.6, 128.5, 128.3, 127.5, 126.4, 126.1, 119.1, 105.4, 101.3, 93.0, 87.0, 66.8, 53.0; IR (KBr): 3488, 3027, 2893, 1721, 1473, 1276, 1261, 1143, 1038, 826, 750, 695 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H22O5Na 449.1365, found 449.1362. (E)-Benzyl 2-(7-(2-Methylstyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ba). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 82% (36.1 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.39−7.35 (m, 1H), 7.34−7.27 (m, 5H), 7.18−7.08 (m, 3H), 6.61 (d, J = 15.6 Hz, 1H), 6.55 (s, 1H), 6.47 (s, 1H), 6.39 (s, 1H), 6.21−6.07 (m, 1H), 5.94 (t, J = 1.1 Hz, 1H), 5.92−5.84 (m, 2H), 5.41−5.29 (m, 1H), 5.26−5.09 (m, 2H), 4.07−3.87 (m, 1H), 2.30 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.1, 153.6, 147.8, 142.0, 139.1, 135.8, 135.4, 135.3, 131.1, 130.2, 129.4, 128.5, 128.3, 128.2, 127.4, 126.2, 126.0, 125.7, 119.4, 105.2, 101.2, 93.0, 87.1, 66.7, 53.4, 19.8; IR (KBr): 3489, 2919, 1721, 1472, 1276, 1261, 1143, 749, 697 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C28H24O5Na 463.1522, found 463.1530. (E)-Benzyl 2-(7-(2-methoxystyryl)-6,7-dihydro-[1,3]dioxolo[4,5f ]benzofuran-6-yl)acrylate (3ca). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 63% (28.7 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.40−7.36 (m, 1H), 7.35−7.26 (m, 5H), 7.24−7.16 (m, 1H), 6.95−6.84 (m, 2H), 6.76 (d, J = 14.1 Hz, 1H), 6.56 (s, 1H), 6.44 (s, 1H), 6.38 (s, 1H), 6.32−6.21 (m, 1H), 5.92 (s, 1H), 5.89 (d, J = 1.3 Hz, 2H), 5.34 (d, J = 6.6 Hz, 1H), 5.27−5.08 (m, 2H), 4.13− 3.94 (m, 1H), 3.83 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 156.6, 153.5, 147.8, 141.9, 139.1, 135.5, 130.2, 128.6, 128.4, 128.2, 126.8, 126.3, 126.2, 125.7, 120.6, 119.7, 110.8, 105.3, 101.2, 93.0, 87.1, 66.7, 55.4, 53.6; IR (KBr): 3694, 2927, 2361, 1722, 1472, 1277, 1144, 750, 695 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C28H24O6Na 479.1471, found 479.1478. (E)-Benzyl 2-(7-(2-Fluorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3da). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 95% (42.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.39−7.35 (m, 1H), 7.34−7.27 (m, 5H), 7.24−7.16 (m, 1H), 7.12−6.98 (m, 2H), 6.56 (t, J = 7.9 Hz, 2H), 6.46 (s, 1H), 6.41−6.31 (m, 2H), 5.93 (s, 1H), 5.91−5.87 (m, 2H), 5.40−5.30 (m, 1H), 5.27−5.15 (m, 2H), 4.07−3.84 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.1, 161.3, 158.9, 153.6, 148.0, 142.0, 139.0, 135.4, 132.4 (J = 4.6 Hz), 128.8 (J = 8.3 Hz), 128.5, 128.2, 127.4, 127.3, 126.1, 124.5, 124.4, 124.0, 123.7, 118.9, 115.6 (J = 21.9 Hz), 105.3, 101.3, 93.0, 86.8, 66.8, 53.4; IR (KBr): 3694, 2977, 1744, 1479, 1277, 1152, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H21FO5Na 467.1271, found 467.1256. 10065

DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

Article

The Journal of Organic Chemistry

CDCl3) δ (ppm): 7.49−7.38 (m, 1H), 7.18−7.07 (m, 3H), 6.67 (d, J = 15.5 Hz, 1H), 6.58 (s, 1H), 6.47 (s, 1H), 6.34 (s, 1H), 6.27−6.14 (m, 1H), 5.99−5.84 (m, 3H), 5.33 (d, J = 6.3 Hz, 1H), 4.23 (q, J = 7.1 Hz, 2H), 4.10−3.94 (m, 1H), 2.34 (s, 3H), 1.33−1.17 (m, 3H); 13 C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.6, 147.8, 141.9, 139.3, 135.9, 135.3, 131.3, 130.2, 129.2, 127.4, 126.1, 125.7, 125.5, 119.4, 105.2, 101.2, 93.0, 87.1, 60.9, 53.4, 19.8, 14.1; IR (KBr): 3546, 2362, 1717, 1457, 1264, 1143, 749 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C23H22O5Na 401.1365, found 401.1382. (E)-Ethyl 2-(7-(2-Fluorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3db). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 77% (29.4 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.51−7.40 (m, 1H), 7.24−7.16 (m, 1H), 7.12−6.99 (m, 2H), 6.70−6.57 (m, 2H), 6.47 (s, 1H), 6.44−6.37 (m, 1H), 6.34 (s, 1H), 6.00−5.87 (m, 3H), 5.40−5.25 (m, 1H), 4.23 (q, J = 6.8 Hz, 2H), 4.05−3.93 (m, 1H), 1.29−1.23 (m, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 160.7, 147.9, 143.8, 142.0, 139.9, 139.3, 136.4, 132.6, 131.5, 128.8, 128.5, 127.3, 127.2, 125.4, 124.1, 124.0, 123.6, 120.5, 118.9, 118.8, 115.8, 105.3, 101.3, 99.9, 93.0, 86.8, 61.0, 53.5, 14.1; IR (KBr): 3694, 2983, 2360, 1746, 1475, 1277, 1158, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C22H19FO5Na 405.1115, found 405.1100. (E)-Ethyl 2-(7-(2-Chlorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3eb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 83% (33.0 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.56−7.49 (m, 1H), 7.38−7.30 (m, 1H), 7.24−7.13 (m, 2H), 6.84 (t, J = 16.1 Hz, 1H), 6.60 (s, 1H), 6.48 (d, J = 10.1 Hz, 1H), 6.36−6.21 (m, 2H), 5.92−5.88 (m, 3H), 5.34 (t, J = 7.3 Hz, 1H), 4.24 (q, J = 7.1 Hz, 2H), 4.06−3.95 (m, 1H), 1.30−1.22 (m, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.6, 148.0, 142.0, 139.3, 134.9, 132.9, 132.8, 129.6, 128.5, 127.4, 126.8, 125.4, 118.9, 105.3, 101.3, 93.0, 86.7, 61.0, 53.3, 14.1; IR (KBr): 3678, 2987, 2362, 1721, 1473, 1262, 1143, 749 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C22H19ClO5Na 421.0819, found 421.0857. (E)-Ethyl 2-(7-(3-Methylstyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3fb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 90% (34.0 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.21−7.13 (m, 3H), 7.11−7.00 (m, 1H), 6.57 (s, 1H), 6.50−6.38 (m, 2H), 6.37−6.26 (m, 2H), 5.98−5.80 (m, 3H), 5.31 (d, J = 6.0 Hz, 1H), 4.32−4.18 (m, 2H), 4.03−3.91 (m, 1H), 2.33 (s, 3H), 1.27 (m, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.7, 147.9, 141.9, 139.3, 138.1, 136.7, 131.3, 129.8, 128.4, 128.3, 127.0, 125.4, 123.5, 119.2, 105.3, 101.2, 93.0, 87.0, 60.9, 53.0, 21.3, 14.1; IR (KBr): 3487, 2362, 1721, 1473, 1265, 1143, 747 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C23H22O5Na 401.1365, found 401.1365. ((E)-Ethyl 2-(7-(3-Chlorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3hb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 95% (37.8 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.35 (s, 1H), 7.25−7.02 (m, 3H), 6.56 (s, 1H), 6.48 (s, 1H), 6.42−6.35 (m, 2H), 6.31 (s, 1H), 5.94−5.86 (m, 3H), 5.37−5.24 (m, 1H), 4.28−4.17 (m, 2H), 3.99−3.88 (m, 1H), 1.30− 1.21 (m, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.7, 148.0, 142.0, 139.2, 138.6, 134.5, 131.7, 129.8, 129.7, 127.4, 126.3, 125.3, 124.5, 118.7, 105.3, 101.3, 93.1, 86.8, 60.9, 52.9, 14.1; IR (KBr): 3468, 2361, 2893, 1721, 1473, 1265, 1143, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C22H19ClO5Na 421.0819, found 421.0840. (E)-Ethyl 2-(7-(4-Methylstyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ib). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 80% (30.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.31−7.26 (m, 1H), 7.25 (s, 1H). 7.11 (d, J = 7.9 Hz, 2H), 6.57 (s, 1H), 6.45 (s, 1H), 6.44−6.35 (m, 1H), 6.32 (s, 1H), 6.31−6.22 (m, 1H), 5.93−5.89 (m, 2H), 5.89−5.83 (m, 1H), 5.30 (d, J = 6.1 Hz, 1H), 4.30−4.16 (m, 2H), 4.02−3.91 (m, 1H), 2.33 (s,

raphy, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 52% (23.7 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.32 (s, 5H), 7.26−7.19 (m, 2H), 6.88−6.77 (m, 2H), 6.53 (s, 1H), 6.46 (s, 1H), 6.38 (s, 1H), 6.36−6.23 (m, 1H), 6.18−6.08 (m, 1H), 5.93−5.91 (m, 1H), 5.91−5.86 (m, 2H), 5.31 (d, J = 6.1 Hz, 1H), 5.21 (s, 2H), 4.01−3.88 (m, 1H), 3.81 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 159.1, 153.6, 147.8, 141.9, 139.1, 135.4, 130.8, 129.5, 128.5, 128.3, 128.2, 127.7, 127.5, 126.1, 119.4, 113.9, 105.4, 101.2, 93.0, 87.1, 66.7, 55.3, 53.0; IR (KBr): 3675, 2977, 1721, 1473, 1276, 1261, 1143, 750 cm−1; HRMS (ESITOF) m/z: [M + Na]+ Calcd for C28H24O6Na 479.1471, found 479.1497. (E)-Benzyl 2-(7-(4-Fluorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ka). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 68% (30.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.29 (d, J = 16.6 Hz, 5H), 7.25−7.18 (m, 2H), 6.97 (t, J = 8.6 Hz, 2H), 6.55 (s, 1H), 6.46 (s, 1H), 6.41−6.28 (m, 2H), 6.25−6.08 (m, 1H), 5.92 (s, 1H), 5.90 (d, J = 1.5 Hz, 2H), 5.32 (d, J = 5.8 Hz, 1H), 5.21 (s, 2H), 4.05−3.84 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.2, 162.3 (J = 245 Hz), 153.7, 147.9, 142.0, 139.0, 135.4, 132.9, 132.8, 130.1, 129.7 (J = 2.2 Hz), 128.5, 128.3, 128.2, 127.9, 127.8, 126.0, 118.9, 115.3 (J = 21.5 Hz), 105.3, 101.3, 93.1, 86.9, 66.8, 52.9; IR (KBr): 3457, 2364, 1720, 1633, 1262, 1143, 1038, 750, 697 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H21FO5Na 467.1271, found 467.1285. (E)-Benzyl 2-(7-(4-Chlorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3la). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 96% (44.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.32 (s, 5H), 7.26−7.16 (m, 4H), 6.55 (s, 1H), 6.46 (s, 1H), 6.38 (s, 1H), 6.31 (d, J = 15.8 Hz, 1H), 6.28−6.20 (m, 1H), 5.92 (s, 1H), 5.91−5.88 (m, 2H), 5.32 (d, J = 5.8 Hz, 1H), 5.21 (s, 2H), 3.99−3.88 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.1, 153.7, 148.0, 142.0, 139.0, 135.4, 135.2, 133.1, 130.6, 130.0, 128.6, 128.5, 128.3, 128.2, 127.6, 126.0, 118.7, 105.3, 101.3, 93.1, 86.8, 66.8, 52.9; IR (KBr): 3701, 2361, 1745, 1477, 1153, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H21ClO5Na 483.0976, found 483.0978. (E)-Benzyl 2-(7-(2-(Thiophen-2-yl)vinyl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ma). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 99% (42.8 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.33 (s, 5H), 7.14 (d, J = 5.0 Hz, 1H), 7.02−6.92 (m, 1H), 6.89 (d, J = 3.2 Hz, 1H), 6.56 (s, 1H), 6.50 (d, J = 15.6 Hz, 1H), 6.45 (s, 1H), 6.38 (s, 1H), 6.22−6.05 (m, 1H), 5.98−5.81 (m, 3H), 5.31 (d, J = 5.8 Hz, 1H), 5.22 (s, 2H), 4.05−3.80 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.1, 153.7, 148.0, 142.0, 141.8, 139.0, 135.4, 129.5, 128.5, 128.3, 127.2, 126.1, 125.6, 124.5, 124.1, 118.8, 105.4, 101.3, 93.0, 86.9, 66.7, 52.7; IR (KBr): 3678, 3027, 1717, 1473, 1276, 1143, 1038, 750 cm−1; HRMS (ESITOF) m/z: [M + Na]+ Calcd for C25H20O5S Na 455.0929, found 455.0963. (E)-Ethyl 2-(7-Styryl-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran6-yl)acrylate (3ab). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 94% (34.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.37 (d, J = 7.3 Hz, 2H), 7.31 (t, J = 7.5 Hz, 2H), 7.23 (t, J = 7.2 Hz, 1H), 6.58 (s, 1H), 6.47 (s, 1H), 6.46−6.24 (m, 3H), 6.01− 5.78 (m, 3H), 5.32 (d, J = 6.0 Hz, 1H), 4.31−4.15 (m, 2H), 4.06− 3.89 (m, 1H), 1.26 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.7, 147.9, 142.0, 139.3, 136.7, 131.2, 130.0, 128.5, 127.5, 126.3, 125.4, 119.2, 105.3, 101.2, 93.0, 87.0, 60.9, 53.0, 14.1; IR (KBr): 3678, 2684, 2360, 1719, 1143, 1284, 745 cm−1; HRMS (ESITOF) m/z: [M + Na]+ Calcd for C22H20O5Na 387.1209, found 387.1230. (E)-Ethyl 2-(7-(2-Methylstyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3bb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 93% (35.2 mg); colorless oil; 1H NMR (400 MHz, 10066

DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069

Article

The Journal of Organic Chemistry

1143, 749, 669 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C24H24O5Na 415.1522, found 415.1555. (E)-Benzyl 2-(6-(4-Nitrophenyl)-7-styryl-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ad). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 55% (30.0 mg); yellow oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 8.07 (d, J = 8.8 Hz, 2H), 7.56 (t, J = 10.6 Hz, 2H), 7.35−7.29 (m, 3H), 7.25−7.16 (m, 5H), 7.08 (d, J = 7.5 Hz, 2H), 6.58 (s, 1H), 6.53 (s, 1H), 6.51−6.41 (m, 2H), 6.22 (s, 1H), 5.91 (s, 2H), 5.54−5.34 (m, 1H), 5.18−4.99 (m, 2H), 4.79 (d, J = 9.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 151.7, 148.2, 147.1, 146.9, 142.6, 142.3, 136.2, 135.2, 132.1, 128.6, 128.4, 128.2, 127.8, 127.7, 127.5, 126.8, 126.2, 122.9, 119.7, 105.2, 101.4, 93.6, 93.5, 66.9, 54.4; IR (KBr): 3415, 2923, 1721, 1474, 1346, 1293, 1149, 1034, 826, 751, 698 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C33H25NO7Na 570.1529, found 570.1534. Procedure for the Synthesis of Compound 5. A solution of 3aa (42.6 mg, 0.1 mmol) and DDQ (27 mg, 0.12 mmol) in toluene (1 mL) was heated to 135 °C and the reaction mixture was refluxed overnight. After stopping the reaction, the reaction mixture was purified through preparative thin layer chromatography to afford pure product 5. Benzyl 8-Phenylbenzo[b][1,3]dioxolo[4,5-f ]benzofuran-6-carboxylate (5). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; yield: 61% (25.7 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 8.25−8.15 (m, 2H), 7.67 (d, J = 7.4 Hz, 2H), 7.57 (d, J = 7.2 Hz, 2H), 7.49 (t, J = 7.6 Hz, 2H), 7.45−7.31 (m, 5H), 7.18 (s, 1H), 6.09 (s, 2H), 5.52 (s, 2H); 13C NMR (100 MHz, CDCl3) δ (ppm): 164.6, 154.9, 152.5, 148.6, 144.8, 140.3, 136.1, 136.0, 128.9, 128.6, 128.2, 128.1, 127.4, 127.1, 126.7, 122.7, 116.0, 115.1, 101.8, 99.2, 94.5, 66.9, 29.7; IR (KBr):3711, 2983, 1699, 1541, 1263, 1168, 747, 688 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C27H18O5Na 445.1046, found 445.1042.

3H), 1.25 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.6, 147.8, 141.9, 139.3, 137.3, 133.9, 131.1, 129.2, 128.9, 126.2, 125.4, 119.3, 105.4, 101.2, 93.0, 87.1, 60.9, 53.0, 27.7, 21.2, 14.1; IR (KBr): 3728, 2360, 1747, 1476, 1276, 1261, 1143, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C23H22O5Na 401.1365, found 401.1358. (E)-Ethyl 2-(7-(4-Methoxystyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3jb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 40% (15.8 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.36−7.27 (m, 2H), 6.90−6.76 (m, 2H), 6.58 (s, 1H), 6.51−6.27 (m, 3H), 6.27−6.11 (m, 1H), 5.94−5.84 (m, 3H), 5.30 (d, J = 6.1 Hz, 1H), 4.31−4.17 (m, 2H), 3.99−3.90 (m, 1H), 3.80 (s, 3H), 1.25 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.4, 159.1, 153.6, 147.8, 141.9, 139.4, 130.7, 129.5, 127.8, 127.5, 125.3, 119.5, 113.9, 105.3, 101.2, 93.0, 87.1, 60.9, 55.3, 53.1, 14.1; IR (KBr): 3848, 2984, 2361, 1457, 1261, 1144, 750, 698 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C23H22O6Na 417.1314, found 417.1343. (E)-Ethyl 2-(7-(4-Fluorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3kb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 42% (16.0 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.36−7.31 (m, 2H), 7.04−6.89 (m, 2H), 6.57 (s, 1H), 6.47 (s, 1H), 6.41 (d, J = 15.8 Hz, 1H), 6.32 (s, 1H), 6.29−6.17 (m, 1H), 5.94−5.86 (m, 3H), 5.31 (d, J = 5.9 Hz, 1H), 4.27−4.18 (m, 2H), 3.99−3.89 (m, 1H), 1.26 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 162.2 (J = 245 Hz), 153.7, 147.9, 142.0, 139.3, 132.9, 130.0, 129.9, 129.8, 127.9, 127.8, 125.3, 119.0, 115.4 (J = 21 Hz), 105.3, 101.3, 93.0, 86.9, 60.9, 53.0, 14.1; IR (KBr): 3629, 2982, 2360, 1719, 1473, 1265, 1165, 747, 669 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C22H19FO5Na 405.1115, found 405.1125. (E)-Ethyl 2-(7-(4-Chlorostyryl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3lb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 81% (32.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.31−7.27 (m, 4H), 6.57 (s, 1H), 6.47 (s, 1H), 6.40 (d, J = 15.8 Hz, 1H), 6.35−6.28 (m, 2H), 5.93−5.90 (m, 2H), 5.89 (t, J = 1.2 Hz, 1H), 5.31 (d, J = 5.8 Hz, 1H), 4.26−4.19 (m, 2H), 3.97−3.91 (m, 1H), 1.26 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.7, 153.0, 148.0, 142.0, 139.2, 135.2, 133.1, 130.8, 129.9, 128.7, 127.5, 125.3, 118.8, 105.3, 101.3, 93.1, 86.8, 60.9, 53.0, 14.1; IR (KBr): 3693, 2983, 1746, 1476, 1157, 750 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C22H19ClO5Na 421.0819, found 421.0842. (E)-Ethyl 2-(7-(2-(Thiophen-2-yl)vinyl)-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3mb). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 81% (30.0 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.14 (d, J = 4.5 Hz, 1H), 7.00−6.90 (m, 2H), 6.56 (d, J = 14.9 Hz, 2H), 6.46 (s, 1H), 6.32 (s, 1H), 6.23−6.14 (m, 1H), 5.94−5.89 (m, 2H), 5.88 (s, 1H), 5.30 (d, J = 5.9 Hz, 1H), 4.23 (q, J = 7.1 Hz, 2H), 3.96−3.89 (m, 1H), 1.27 (t, J = 7.2 Hz, 3H); 13 C NMR (100 MHz, CDCl3) δ (ppm): 165.3, 153.7, 147.9, 142.0, 141.8, 139.3, 129.7, 127.3, 125.6, 125.4, 124.4, 124.1, 118.8, 105.3, 101.3, 93.0, 86.9, 61.0, 52.8, 14.1; IR (KBr): 3690, 2961, 1718, 1473, 1276, 1265, 1143, 748 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C20H18O5SNa 393.0773, found 393.0794. (E)-tert-Butyl 2-(7-Styryl-6,7-dihydro-[1,3]dioxolo[4,5-f ]benzofuran-6-yl)acrylate (3ac). Preparative thin layer chromatography, petroleum ether/ethyl acetate = 10/1; reaction time = 12 h; dr >95:5; yield: 77% (30.2 mg); colorless oil; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.37 (d, J = 7.3 Hz, 2H), 7.33−7.27 (m, 2H), 7.23 (t, J = 7.2 Hz, 1H), 6.57 (s, 1H), 6.45 (t, J = 7.8 Hz, 2H), 6.37−6.28 (m, 1H), 6.23 (s, 1H), 5.90 (d, J = 2.3 Hz, 2H), 5.79 (s, 1H), 5.29 (d, J = 6.2 Hz, 1H), 3.99−3.92 (m, 1H), 1.44 (s, 9H); 13C NMR (100 MHz, CDCl3) δ (ppm): 164.5, 153.8, 147.8, 141.9, 140.7, 136.7, 131.3, 130.1, 128.5, 127.5, 126.3, 124.6, 119.3, 105.3, 101.2, 93.0, 87.1, 81.5, 53.2, 28.0; IR (KBr): 3628, 2361, 1684, 1473, 1276, 1261,

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.8b01390. General synthetic route for catalysts 4, 1H and 13C NMR spectra of substrate S3c and products 3 and 5, HPLC spectra of product 3aa, H−H COSY, HMQC, HMBC, and NOSY spectra of product 3aa (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Feng Shi: 0000-0003-3922-0708 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are grateful for financial support from National Natural Science Foundation of China (21772069), Natural Science Foundation of Jiangsu Province (BK20160003), Six Kinds of Talents Project of Jiangsu Province (SWYY-025), and Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX18_2107).

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REFERENCES

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The Journal of Organic Chemistry Methides. Synthesis 2015, 47, 3629−3644. (c) Jaworski, A. A.; Scheidt, K. A. Emerging Roles of in Situ Generated Quinone Methides in Metal-Free Catalysis. J. Org. Chem. 2016, 81, 10145− 10153. (2) For early examples on catalytic asymmetric substitutions of oQMs: (a) Wilcke, D.; Herdtweck, E.; Bach, T. Enantioselective Brønsted Acid Catalysis in the Friedel-Crafts Reaction of Indoles with Secondary ortho-Hydroxybenzylic Alcohols. Synlett 2011, 2011, 1235−1238. (b) Luan, Y.; Schaus, S. E. Enantioselective Addition of Boronates to o-Quinone Methides Catalyzed by Chiral Biphenols. J. Am. Chem. Soc. 2012, 134, 19965−19968. (3) For selected examples on catalytic asymmetric substitutions of oQMs: (a) Zhao, W.; Wang, Z.; Chu, B.; Sun, J. Enantioselective Formation of All-Carbon Quaternary Stereocenters from Indoles and Tertiary Alcohols Bearing A Directing Group. Angew. Chem., Int. Ed. 2015, 54, 1910−1913. (b) Saha, S.; Alamsetti, S. K.; Schneider, C. Chiral Brønsted Acid-Catalyzed Friedel−Crafts Alkylation of Electron-Rich Arenes with in situ-generated ortho-Quinone Methides: Highly Enantioselective Synthesis of Diarylindolylmethanes and Triarylmethanes. Chem. Commun. 2015, 51, 1461−1464. (c) Huang, Y.; Hayashi, T. Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines. J. Am. Chem. Soc. 2015, 137, 7556−7559. (d) Wang, Z.; Ai, F.; Wang, Z.; Zhao, W.; Zhu, G.; Lin, Z.; Sun, J. Organocatalytic Asymmetric Synthesis of 1, 1-Diarylethanes by Transfer Hydrogenation. J. Am. Chem. Soc. 2015, 137, 383−389. (e) Guo, W.; Wu, B.; Zhou, X.; Chen, P.; Wang, X.; Zhou, Y.-G.; Liu, Y.; Li, C. Formal Asymmetric Catalytic Thiolation with a Bifunctional Catalyst at a Water−Oil Interface: Synthesis of Benzyl Thiols. Angew. Chem., Int. Ed. 2015, 54, 4522−4526. (f) Caruana, L.; Mondatori, M.; Corti, V.; Morales, S.; Mazzanti, A.; Fochi, M.; Bernardi, L. Catalytic Asymmetric Addition of Meldrum’s Acid, Malononitrile, and 1, 3Dicarbonyls to ortho-Quinone Methides Generated In Situ Under Basic Conditions. Chem. - Eur. J. 2015, 21, 6037−6041. (g) Zhu, Y.; Zhang, L.; Luo, S. Asymmetric Retro-Claisen Reaction by Chiral Primary Amine Catalysis. J. Am. Chem. Soc. 2016, 138, 3978−3981. (4) For early examples on catalytic asymmetric [4 + 2] cyclizations of o-QMs: (a) Alden-Danforth, E.; Scerba, M. T.; Lectka, T. Asymmetric Cycloadditions of o-Quinone Methides Employing Chiral Ammonium Fluoride Precatalysts. Org. Lett. 2008, 10, 4951−4953. (b) Lv, H.; You, L.; Ye, S. Enantioselective Synthesis of Dihydrocoumarins via N-Heterocyclic Carbene-Catalyzed Cycloaddition of Ketenes and o-Quinone Methides. Adv. Synth. Catal. 2009, 351, 2822−2826. (c) El-Sepelgy, O.; Haseloff, S.; Alamsetti, S. K.; Schneider, C. Brønsted Acid Catalyzed, Conjugate Addition of βDicarbonyls to In Situ Generated ortho-Quinone Methides Enantioselective Synthesis of 4-Aryl-4H-Chromenes. Angew. Chem., Int. Ed. 2014, 53, 7923−7927. (d) Hsiao, C. C.; Liao, H. H.; Rueping, M. Enantio- and Diastereoselective Access to Distant Stereocenters Embedded within Tetrahydroxanthenes: Utilizing ortho-Quinone Methides as Reactive Intermediates in Asymmetric Brønsted Acid Catalysis. Angew. Chem., Int. Ed. 2014, 53, 13258−13263. (5) For selected examples on catalytic asymmetric [4 + 2] cyclizations of o-QMs: (a) Tsui, G. C.; Liu, L.; List, B. The Organocatalytic Asymmetric Prins Cyclization. Angew. Chem., Int. Ed. 2015, 54, 7703−7706. (b) Hu, H.; Liu, Y.; Guo, J.; Lin, L.; Xu, Y.; Liu, X.; Feng, X. Enantioselective Synthesis of Dihydrocoumarin Derivatives by Chiral Scandium(III)-Complex Catalyzed InverseElectron-Demand Hetero-Diels−Alder Reaction. Chem. Commun. 2015, 51, 3835−3837. (c) Lee, A.; Scheidt, K. A. N-Heterocyclic Carbene-Catalyzed Enantioselective Annulations: A Dual Activation Strategy for A Formal [4 + 2] Addition for Dihydrocoumarins. Chem. Commun. 2015, 51, 3407−3410. (d) Alamsetti, S. K.; Spanka, M.; Schneider, C. Synergistic Rhodium/Phosphoric Acid Catalysis for the Enantioselective Addition of Oxonium Ylides to ortho-Quinone Methides. Angew. Chem. 2016, 128, 2438−2442. (e) Chen, P.; Wang, K.; Guo, W.; Liu, X.; Liu, Y.; Li, C. Enantioselective Reactions of 2Sulfonylalkyl Phenols with Allenic Esters: Dynamic Kinetic Resolution and [4 + 2] Cycloaddition Involving ortho-Quinone Methide

Intermediates. Angew. Chem., Int. Ed. 2017, 56, 3689−3693. (f) Wang, Z.; Sun, J. Enantioselective [4 + 2] Cycloaddition of o-Quinone Methides and Vinyl Sulfides: Indirect Access to Generally Substituted Chiral Chromanes. Org. Lett. 2017, 19, 2334−2337. (g) Wang, Z.; Wang, T.; Yao, W.; Lu, Y. Phosphine-Catalyzed Enantioselective [4 + 2] Annulation of o-Quinone Methides with Allene Ketones. Org. Lett. 2017, 19, 4126−4129. (6) For catalytic asymmetric [4 + 2] cyclizations of o-QMs from our group: (a) Zhao, J.-J.; Sun, S.-B.; He, S.-H.; Wu, Q.; Shi, F. Catalytic Asymmetric Inverse-Electron-Demand Oxa-Diels−Alder Reaction of In Situ Generated ortho-Quinone Methides with 3-Methyl-2-Vinylindoles. Angew. Chem., Int. Ed. 2015, 54, 5460−5464. (b) Zhao, J.-J.; Zhang, Y.-C.; Xu, M.-M.; Tang, M.; Shi, F. Catalytic Chemo-, E/Z-, and Enantioselective Cyclizations of o-Hydroxybenzyl Alcohols with Dimedone-Derived Enaminones. J. Org. Chem. 2015, 80, 10016− 10024. (c) Zhang, Y.-C.; Zhu, Q.-N.; Yang, X.; Zhou, L.-J.; Shi, F. Merging Chiral Brønsted Acid/Base Catalysis: An Enantioselective [4 + 2] Cycloaddition of o-Hydroxystyrenes with Azlactones. J. Org. Chem. 2016, 81, 1681−1688. (7) For selected examples on [4 + 3] cyclizations of o-QMs: (a) Lv, H.; Jia, W.-Q.; Sun, L.-H.; Ye, S. N-Heterocyclic Carbene Catalyzed [4 + 3] Annulation of Enals and o-Quinone Methides: Highly Enantioselective Synthesis of Benzo-ε-Lactones. Angew. Chem., Int. Ed. 2013, 52, 8607−8610. (b) Izquierdo, J.; Orue, A.; Scheidt, K. A. A Dual Lewis Base Activation Strategy for Enantioselective CarbeneCatalyzed Annulations. J. Am. Chem. Soc. 2013, 135, 10634−10637. (c) Mei, G.-J.; Zhu, Z.-Q.; Zhao, J.-J.; Bian, C.-Y.; Chen, J.; Chen, R.W.; Shi, F. Brønsted Acid-Catalyzed Stereoselective [4 + 3] Cycloadditions of ortho-Hydroxybenzyl Alcohols with N,N′-Cyclic Azomethine Imines. Chem. Commun. 2017, 53, 2768−2771. (8) For [4 + 1] cyclizations of o-QMs with sulfur ylides: (a) Chen, M.-W.; Cao, L.-L.; Ye, Z.-S.; Jiang, G.-F.; Zhou, Y.-G. A Mild Method for Generation of o-Quinone Methides under Basic Conditions. The Facile Synthesis of trans-2, 3-Dihydrobenzofurans. Chem. Commun. 2013, 49, 1660−1662. (b) Wu, B.; Chen, M.-W.; Ye, Z.-S.; Yu, C.-B.; Zhou, Y.-G. A Streamlined Synthesis of 2, 3-Dihydrobenzofurans via the ortho-Quinone Methides Generated from 2-Alkyl-Substituted Phenols. Adv. Synth. Catal. 2014, 356, 383−387. (c) Lei, X.; Jiang, C.H.; Wen, X.; Xu, Q.-L.; Sun, H. Formal [4 + 1] Cycloaddition of oQuinone Methides: Facile Synthesis of Dihydrobenzofurans. RSC Adv. 2015, 5, 14953−14957. (d) Yang, Q.-Q.; Xiao, W.-J. Catalytic Asymmetric Synthesis of Chiral Dihydrobenzofurans through a Formal [4 + 1] Annulation Reaction of Sulfur Ylides and In Situ Generated ortho-Quinone Methides. Eur. J. Org. Chem. 2017, 2017, 233−236. (9) For [4 + 1] cyclizations of o-QMs with pyridinium methylides: Osyanin, V. A.; Osipov, D. V.; Klimochkin, Y. N. Reactions of oQuinone Methides with Pyridinium Methylides: A Diastereoselective Synthesis of 1,2-Dihydronaphtho[2,1-b]furans and 2,3-Dihydrobenzofurans. J. Org. Chem. 2013, 78, 5505−5520. (10) For [4 + 1] cyclizations of o-QMs with in situ-generated oxyphosphonium enolates: Rodriguez, K. X.; Vail, J. D.; Ashfeld, B. L. Phosphorus(III)-Mediated Stereoconvergent Formal [4 + 1]-Cycloannulation of 1,2-Dicarbonyls and o-Quinone Methides: A Multicomponent Assembly of 2,3-Dihydrobenzofurans. Org. Lett. 2016, 18, 4514−4517. (11) For [4 + 1] cyclizations of o-QMs with aldehydes: Xie, Y.; Yu, C.; Que, Y.; Li, T.; Wang, Y.; Lu, Y.; Wang, W.; Shen, S.; Yao, C. NHeterocyclic Carbene-Triggered Transition-Metal-Free Synthesis of 2, 3-Disubstituted Benzofuran Derivatives. Org. Biomol. Chem. 2016, 14, 6463−6469. (12) For [4 + 1] cyclizations of o-QMs with ammonium ylides: Meisinger, N.; Roiser, L.; Monkowius, U.; Himmelsbach, M.; Robiette, R.; Waser, M. Asymmetric Synthesis of 2,3-Dihydrobenzofurans by a [4 + 1] Annulation between Ammonium Ylides and In Situ Generated o-Quinone Methides. Chem. - Eur. J. 2017, 23, 5137− 5142. (13) For [4 + 1] cyclizations of o-QMs with bromomalonates: Lian, X.-L.; Adili, A.; Liu, B.; Tao, Z.-L.; Han, Z.-Y. Enantioselective [4 + 1] 10068

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The Journal of Organic Chemistry Cycloaddition of ortho-Quinone Methides and Bromomalonates under Phase-Transfer Catalysis. Org. Biomol. Chem. 2017, 15, 3670− 3673. (14) For [4 + 1] cyclizations of o-QMs with 3-chlorooxindoles: Jiang, X.-L.; Liu, S.-J.; Gu, Y.-Q.; Mei, G.-J.; Shi, F. Catalytic Asymmetric [4+ 1] Cyclization of ortho-Quinone Methides with 3Chlorooxindoles. Adv. Synth. Catal. 2017, 359, 3341−3346. (15) For some examples using MBH carbonates as one-carbon synthons: (a) Zhang, X.-N.; Deng, H.-P.; Huang, L.; Wei, Y.; Shi, M. Phosphine-Catalyzed Asymmetric [4 + 1] Annulation of Morita− Baylis−Hillman Carbonates with Dicyano-2-methylenebut-3-enoates. Chem. Commun. 2012, 48, 8664−8666. (b) Hu, F.-L.; Wei, Y.; Shi, M. Phosphine-Catalyzed Asymmetric [4 + 1] Annulation of Activated α,β-Unsaturated Ketones with Morita−Baylis−Hillman Carbonates: Enantioselective Synthesis of Spirooxindoles Containing Two Adjacent Quaternary Stereocenters. Chem. Commun. 2014, 50, 8912−8914. (c) Zhan, G.; Shi, M.-L.; He, Q.; Lin, W.-J.; Ouyang, Q.; Du, W.; Chen, Y.-C. Catalyst-Controlled Switch in Chemo- and Diastereoselectivities: Annulations of Morita−Baylis−Hillman Carbonates from Isatins. Angew. Chem., Int. Ed. 2016, 55, 2147−2151. (d) Cheng, Y.; Han, Y.; Li, P. Organocatalytic Enantioselective [1 + 4] Annulation of Morita−Baylis−Hillman Carbonates with ElectronDeficient Olefins: Access to Chiral 2,3-Dihydrofuran Derivatives. Org. Lett. 2017, 19, 4774−4777. (16) For some reviews on phosphine catalysis: (a) Lu, X.; Zhang, C.; Xu, Z. Reactions of Electron-Deficient Alkynes and Allenes under Phosphine Catalysis. Acc. Chem. Res. 2001, 34, 535−544. (b) Wang, Z.; Xu, X.; Kwon, O. Phosphine Catalysis of Allenes with Electrophiles. Chem. Soc. Rev. 2014, 43, 2927−2940. (c) Li, W.; Zhang, J. Recent Developments in the Synthesis and Utilization of Chiral β-Aminophosphine Derivatives as Catalysts or Ligands. Chem. Soc. Rev. 2016, 45, 1657−1677. (d) Wang, T.; Han, X.; Zhong, F.; Yao, W.; Lu, Y. Amino Acid-Derived Bifunctional Phosphines for Enantioselective Transformations. Acc. Chem. Res. 2016, 49, 1369− 1378. (17) Zhang, H.-H.; Wang, C.-S.; Li, C.; Mei, G.-J.; Li, Y.; Shi, F. Design and Enantioselective Construction of Axially Chiral NaphthylIndole Skeletons. Angew. Chem., Int. Ed. 2017, 56, 116−121. (18) (a) Qin, Z.; Liu, W.; Wang, D.; He, Z. Phosphine-Catalyzed (4 + 1) Annulation of o-Hydroxyphenyl and o-Aminophenyl Ketones with Allylic Carbonates: Syntheses and Transformations of 3Hydroxy-2,3-Disubstituted Dihydrobenzofurans and Indolines. J. Org. Chem. 2016, 81, 4690−4700. (b) Li, H.; Luo, J.; Li, B.; Yi, X.; He, Z. Enantioselective [4 + 1]-Annulation of α,β-Unsaturated Imines with Allylic Carbonates Catalyzed by a Hybrid P-Chiral Phosphine Oxide−Phosphine. Org. Lett. 2017, 19, 5637−5640. (19) Li, H.; Chen, Q.; Lu, Z.; Li, A. Total Syntheses of Aflavazole and 14-Hydroxyaflavinine. J. Am. Chem. Soc. 2016, 138, 15555− 15558.

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DOI: 10.1021/acs.joc.8b01390 J. Org. Chem. 2018, 83, 10060−10069