Enantioselective Synthesis of β-Allenoates via Phosphine Catalysed

Nov 24, 2017 - The intermediate propargylamine was isolated in 50% yield and converted to give the β-allenoate 10aa in 68% yield and 96% ee upon reac...
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Article Cite This: J. Org. Chem. 2018, 83, 267−274

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Enantioselective Synthesis of β‑Allenoates via Phosphine-Catalyzed and ZnI2‑Promoted Preparation of Oxazolidines and Propargylamines Using Chiral Amines, 1‑Alkynes, and Propiolates Mariappan Periasamy,* Lakavathu Mohan, Iddum Satyanarayana, and Polimera Obula Reddy School of Chemistry, University of Hyderabad Central University P.O., Hyderabad, 500046 Telangana, India S Supporting Information *

ABSTRACT: Diphenylphosphinoethane (DPPE)-catalyzed and ZnI2-promoted in situ formation of oxazolidine, alkynyl zinc, and propargylamine intermediates from 1-alkynes, chiral (S)-diphenyl(pyrrolidin-2-yl)methanol, and propiolates gave the corresponding chiral (R)-β-allenoates in 40−72% yield with up to >99% ee. The intermediate propargylamine was isolated in 50% yield and converted to give the β-allenoate 10aa in 68% yield and 96% ee upon reaction with ZnI2. The results are discussed considering a mechanism involving oxazolidine and iminium ions formed in situ followed by addition of alkynyl zinc complex to produce the propargylamine that gives the corresponding allenoate via a 1,5hydrogen shift in the presence of ZnI2.

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INTRODUCTION In recent years, there has been immense interest in the development of methods for synthesis of chiral allenes.1 The recently reported methods2 to readily access allenes with very high optical purities made these derivatives more than academic curiosity. Since several naturally occurring and biologically active allenic compounds were also reported,3 practical methods to access chiral allenes gained importance. Previously, methods for highly enantioselective synthesis of disubstituted chiral allenes using chiral secondary amines, 1-alkynes, and aldehydes were reported.4 More recently, trisubstituted allenes were prepared via CuCl promoted hydroamination of alkynes using chiral amine derivatives (Scheme 1).4e Very recently, the asymmetric method was reported for the preparation of chiral disubstituted allenes via coupling of diazo compounds and propargylamine.4f Herein, we report the results on the biphosphine catalyzed and zinc halide promoted enantioselective synthesis of chiral allenoates with up to 72% yield and 99% ee, using ethyl propiolate, 1-alkynes, and the commercially available chiral secondary amine 11.

corresponding enamine derivative 8 was obtained in 70% yield.4d We have observed that the enamine derivative could be converted to the corresponding (R)-β-allenoate 10aa upon reaction with phenylacetylene and ZnI2 for 12 h at 120 °C but only in 5% yield (Scheme 2). Presumably, the enamine intermediate I reacts with the alkenyl zinc complex produced in situ to give the intermediate II which affords the allenoate in low yield besides a complex mixture of unidentified products. We then examined the use of different readily accessible optically active chiral secondary amines, 1, 2, and 11 in a single pot reaction under these conditions (Scheme 3). We have found that when the reaction was carried out using chiral amine 11, the corresponding allene (R)-10aa was obtained in 10% yield and 92% ee. Whereas the reaction using chiral secondary amine 1 gave the product (R)-10aa in 5% yield and 90% ee, the chiral secondary amine 2 afforded the product (R)-10aa in 10% yield and 92% ee besides a complex mixture of unidentified products. Presumably, intermediates similar to the compound 8 which are expected to be formed are unstable under the present reaction conditions. Recently, asymmetric synthesis of oxazolidine derivatives was reported by a biphosphine catalyzed synthetic protocol.11 Also, a two-step synthesis involving preparation of oxazolidine derivative using benzaldehyde and its conversion to allene was also reported.8a Accordingly, we envisaged the preparation of the oxazolidine in situ by phosphine catalysis followed by preparation of alkynyl zinc compounds in situ using 1-alkynes to access the corresponding β-allenoates (Scheme 4).

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RESULTS AND DISCUSSION Chiral allenoates5,6 are an important class of compounds potentially useful for further synthetic exploitation.7,8 Over the years, a few methods have been reported for the synthesis of βallenoates but with limited scope.9,10 It was of interest to us to examine whether hydroamination methodology reported previously would be applicable to the enantioselective synthesis of chiral β-allenoates. Accordingly, we carried out an experiment using ethyl propiolate 7a and chiral amine 1, but only the © 2017 American Chemical Society

Received: October 17, 2017 Published: November 24, 2017 267

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

Article

The Journal of Organic Chemistry Scheme 1. Hydroamination Route for Allene Synthesis

Scheme 2. Synthesis of Enamine Derivative and its Conversion to β-Allenoate

Scheme 3. Reaction of Different Optically Active Chiral Secondary Amines

Table 1. Reaction of Different Phosphine Catalysts with Chiral Amines, Ethyl Propiolate 7a, and Phenylacetylene 9a

Scheme 4. Reaction of Oxazolidine Intermediate with 1Alkyne and ZnI2

entry

catalysta

amine

mol (%)

10aa (%)

eec (%)

1 2 3 4 5b 6b 7b 8 9

PPh3 PPh3 PPh3 PPh3 PCy3 DPPEd DPPPd DPPBd DPPPentd

11 1 2 11 11 11 11 11 11

5 5 5 10 10 5 5 5 5

20 5 10 20 10 62 65 65 68

92 90 92 92 90 99 92 93 90

a

All reactions were performed using 1.0 mmol of chiral amines, 1.0 mmol of 9a, 1.0 mmol of ethyl propiolate 7a, and 5 mol% of the catalyst at 120 °C for 12 h. bThese reactions were run for 10−12 h. c The ee was determined by chiral HPLC analysis. dDPPE, DPPP, DPPB, and DPPPent are acronyms for diphenylphosphinoethane, -propane, -butane, and -pentane, respectively.

In the initial experiments, we have examined the efficacy of phosphine catalyst to initiate the hydroamination of the propiolate. We have chosen the ethyl propiolate 7a, phenylacetylene 9a, and chiral secondary cyclic amines, 1, 2, and 11 for the optimization of reaction conditions using PPh3. The results are presented in Table 1. The chiral β-allenoate (R)10aa was obtained in 20% yield with 92% ee when PPh3 was used as a catalyst but the yield is still poor (Table 1, entry 1). However, replacement of chiral amine 11 with other chiral secondary amines, such as 1 and 2, resulted in the very low

conversion of the substrates (Table 1, entry 2 and 3). Also, the corresponding (R)-10aa was obtained only in 20% yield using 10 mol % of catalyst (Table 1, entry 4). The lower yield could be attributed to the absence of hydroxyl group in chiral amine 1 and 2. When the tricyclohexyl phosphine (PCy3) was used, the 268

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

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The Journal of Organic Chemistry

corresponding β-allenoate was obtained in 10% yield and 90% ee (entry 5, Table 1). Fortunately, the diphenylphosphinoethane (DPPE) catalysis enhanced the yield of the (R)-β-allenoate (62% yield and 99% ee, entry 6, Table 1). We have tested the applicability of other biphosphines and the results are presented in Table 1. The diphenylphosphinopropane (DPPP) led to moderate improvement in yield (65%) of chiral β-allenoate (R)-10aa with 92% ee (entry 7, Table 1). Also, the use of diphenyl phosphinobutane (DPPB) gave the corresponding allene (R)-10aa in 65% yield with 93% ee, and diphenylphosphinopentane (DPPPent) gave the β-allenoate (R)-10aa in good yield (68%) and selectivity (90% ee) (entry 8 and 9, Table 2). We have also studied the reaction of ZnCl2, ZnBr2, and ZnI2promoted chiral β-allenoate synthesis using DPPE as the catalyst. The ZnCl2 and ZnBr2 gave the chiral β-allenoate in low yield (entry 1 and 2, Table 2). However, the use of ZnI2promoted reaction gave the chiral β-allenoate in 62% yield with an excellent enantioselectivity (99% ee) (entry 3, Table 2). The reaction temperature was also found to be crucial for this transformation. An elevating the temperature above 120 °C led

Table 2. Reaction of Different Metal Salts and Solvents with Chiral Amine 11, DPPE, Ethyl Propiolate, and Phenylacetylenea

S.No

solvent

temp. °C

MXn

time (h)b

10aac

eed

1 2 3 4 5 6

toluene toluene toluene toluene toluene dioxane

120 110 120 140 110 100

ZnCl2 ZnBr2 ZnI2 ZnI2 ZnI2 ZnI2

15 12 10 10 10 15

20 50 62 68 55 20

90 99 99 85 99 92

a The reaction was performed using amine 11, 1 mmol of 9a, 1.0 mmol of 7a, and 5 mol % of the DPPE. bThese reactions were run for 10−15 h. cYields of β-allenoate. dThe ee was determined by chiral HPLC analysis.

Table 3. Synthesis of β-Allenoatesa,b,c

a The reactions were carried out by using amine 11 (1.0 mmol), propiolates 7 (1.0 mmol), DPPE (5 mol %), and 1-alkynes 9 (1.0 mmol) in toluene (3 mL) at 120 °C for 10−14 h. bYields of β-allenoate. cThe ee was determined by chiral HPLC analysis. dThe ee could not be determined by chiral HPLC as the AD-H, AS-H, OB-H, OD-H, and OJ-H columns available with us failed to separate the enantiomers of 10ka, 10la, and 10ad.

269

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

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The Journal of Organic Chemistry to the formation of chiral β-allenoate 10aa in 68% yield (entry 4, Table 2), whereas lowering the temperature to 110 °C resulted in 55% yield of chiral β-allenoate 10aa (entry 5, Table 2). In dioxane solvent, this transformation gave the chiral βallenoate 10aa in 20% yield (entry 6, Table 2). Thus, ZnI2 gave the better optimum result under this condition (entry 3, Table 2). Under the optimum conditions, we have examined the substrate scope using various 1-alkynes. As shown in Table 3, when the alkynes with 9b, 9c, 9d, and 9e R1 groups 4-Me-, 3Me-, 4-OMe-, and 3-OMe-substitution in the phenyl ring react with ethyl propiolate 7a to give the (R)-β-allenoates 10ba− 10ae in good yields with very good enantioselectivities (Table 3). In addition, alkynes substituted with 4-tert-butyl-, 4-propyl, and 4-pentyl groups in the phenyl ring 9f, 9g, and 9h also gave the allenoates with excellent enantioselectivity (Table 3, 10fa− 10ha). Also, alkynes 9i, 9j, and 9l with electron withdrawing 4F-, 3-F-, and 4-Cl, resulted in the formation of the allenoates in 40−60% yields with 96−99% ee (Table 3, 10ia, 10ja, and 10la). Similarly, the alkyne 9k with 4-Ph substitution gave the corresponding (R)-β-allenoate in 70% yield (Table 3, 10ka). We have also examined the use of propiolate esters containing various R2 groups, such as 3-phenylpropyl 7b, 4-phenylpropyl 7c, and pent-4-en-1-yl 7d and obtained the corresponding βallenoates 10ab−10ad in 41−60% yield with 98−99% ee (Table 3). Unfortunately, the enantiomeric purity of the compounds 10ka, 10la, and 10ad could not be determined by chiral HPLC analysis as the AD-H, AS-H, OB-H, OD-H, and OJ-H columns available with us failed to separate the enantiomers of these compounds. However, comparison of specific rotation values of compounds 10ka, 10la, and 10ad with similar reported derivatives would suggest that the optical purities of these compounds are expected to be also very high (Supporting Information, Table S2). All the optically active β-allenoates obtained by using chiral amine 11 are levorotatory from which the absolute configurations of the major enantiomer of the chiral allenes are assigned as R according to the Lowe−Brewster rule12 and the previous studies.4 We have also carried out an experiment to isolate the propargylamine intermediate 13 that is expected to form in this transformation by stopping the reaction after 5 h (Scheme 5).

mixture after removing toluene solvent which indicated the presence of the oxazolidine 12 and enamine derivative 14 (Scheme 6) (see Supporting Information). However, upon Scheme 6. Isolation of Intermediate Enamine Derivative 14 and β-Allenoate

silica gel column chromatography, the reaction mixture gave only the enamine derivative 14. The structure of the enamine product 14 was confirmed by single crystal X-ray analysis (Supporting Information). Presumably, the oxazolidine derivative present in the mixture is also converted to the enamine derivative 14 in the presence of silica gel.13 We have observed that the enamine derivative 14, upon reaction with 1-alkyne, afforded the β-allenoate 10aa in only 10% yield and 92% ee (Scheme 6). We have also attempted the reaction of 1-alkynes 3a and 3b with alkyl substitution with ethyl propiolate 7a, DPPE, and chiral amine 11 in toluene. It was found that the reaction did not give the desired β-allenoate but gave the corresponding propargylamine derivatives 15 in 33−38% yield along with some unidentified products (Scheme 7). Scheme 7. Isolation of Propargylamine Derivative 15

Scheme 5. Isolation of Propargylamine Derivative 13

In this case, the oxazolidine 12 that is expected to be formed in situ, reacts with aliphatic 1-alkynes in the presence of ZnI2 to afford the propargylamines in low yield due to lesser reactivity of the aliphatic 1-alkyne toward oxazolidine derivative 12 compared to aromatic 1-alkynes. Also, the propargylamine derivatives 15 upon reaction with ZnI2 did not give the desired β-allenoate 10aa. In this case, however, only the enynoate 16 obtained in 48−50% yield (Scheme 7).

In this case, the propargylamine 13 was obtained in 50% yield besides the allenoate 10aa (5% yield). Also, the propargylamine intermediate 13 is readily converted to the chiral β-allenoate 10aa upon reaction with ZnI2 (Scheme 5). We have examined the intermediates involved in this transformation by recording the NMR spectrum of the reaction 270

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

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The Journal of Organic Chemistry Scheme 8. Plausible Mechanism for Chiral β-Allenoates

designing methods to access these potentially useful multifunctional synthons for further synthetic exploitation.

A tentative reaction mechanism depicted in Scheme 8 may be considered for the formation of allenoates.4,11,14 Initially, the intermediate 18 would be formed by the conjugate addition of biphosphine to the electron-deficient propiolate. The chiral amine 11 would be deprotonated by intermediate 18. Subsequent conjugate addition would generate the intermediate 19 which could undergo intramolecular Michael addition and elimination of the biphosphine to generate the cyclized oxazolidine product 12 and the iminium species 20. Reaction of the alkynyl zinc formed in situ with the intermediate 20 would result in the formation of the propargylamine 23. Subsequently, complexation with ZnI 2 would give the intermediate 24 which after an intramolecular hydride shift and addition of the H and ZnI group across the triple bond would give the intermediate 25. After elimination of ZnI2 and the imine 26, the chiral (R)-β-allenoate 10 would be formed. The spectral data of the imine byproduct 26 isolated showed 1:1 correspondence with the reported data.4a The byproduct 26 could be easily reduced to isolate the starting chiral diphenylprolinol 11 for reuse by adding sodium borohydride in methanol at −20 °C before workup and bringing the contents to 25 °C and stirring for 2 h following a reported procedure.4a

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EXPERIMENTAL SECTION

General Information. Melting points were determined using a capillary point apparatus. IR (KBr) spectra and neat IR spectra were recorded with polystyrene as reference. 1H-NMR (400 MHz) and 13C{1H}NMR (100 MHz) spectra were recorded with chloroform-d as solvent and TMS as reference (δ= 0 ppm). The chemical shifts are expressed in δ downfield from the signal of internal TMS. Highresolution mass spectra (HRMS) were recorded on micromass ESITOF. Optical rotations were measured using automatic polarimeters (readability ±0.001°). The condition of the polarimeter was checked by measuring the optical rotation of a standard S-(−)-diphenyl prolinol, 99% ee (S-DPP). Analytical grade ZnCl2, ZnBr2, and ZnI2 samples were heated at 120 °C under reduced pressure (0.001 mmHg) in a vacuum oven and stored under dry nitrogen at room temperature. Toluene was freshly distilled over sodium-benzophenone ketyl before use. Analytical thin layer chromatographic tests were carried out on glass plates (3 × 10 cm) coated with 250mμ silica gel-G and GF254 containing 13% calcium sulfate as binder. The spots were visualized by short exposure to iodine vapor or UV light. Column chromatography was carried out using silica gel (100−200 mesh) and neutral alumina. General Procedure for Synthesis of Chiral β-Allenoates. To a stirred solution of amine 11 (1 mmol) in toluene (3 mL), DPPE (0.020 g, 0.005 mmol), and propiolates 7a (0.108 mL, 1.0 mmol) and the contents were stirred for 1.5 h. Then ZnI2 (0.160 g, 0.5 mmol) and 1-alkyne 9 (1 mmol) were added and the reaction mixture was stirred at 120 °C for 10 h. The reaction mixture cooled to room temperature. Toluene was removed using reduced pressure. Water (5 mL) and DCM (15 mL) were added. The DCM layer was washed with saturated NaCl solution, dried (Na2SO4), and concentrated. The residue was subjected to column chromatography using hexane and ethyl acetate (95:5) as eluent to isolate the allenoates 10. General Procedure for Chiral Enamine Intermediate. To a stirred solution of amine 11 (1 mmol) in toluene (3 mL), DPPE

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CONCLUSION We have developed a method for the highly enantioselective synthesis of chiral β-allenoates from 1-alkynes, propiolates, and chiral secondary amines via the corresponding transient oxazolidine intermediates and propargylamine derivatives. Methods for isolation of oxazolidine, enamine, and propargylamine intermediates and subsequent zinc iodide promoted conversion to chiral β-allenoate 10 should be helpful in 271

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

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The Journal of Organic Chemistry

125.8, 125.4, 85.8, 76.4, 67.6, 60.5, 50.2, 48.3, 40.6, 31.9, 29.4, 29.3, 29.1, 29.0, 28.8, 23.7, 22.7, 18.6, 14.2, 14.1; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C32H44NO3: 490.3321 found: 490.3329. Ethyl 3-(2-(Hydroxydiphenylmethyl)pyrrolidin-1-yl)undec-4ynoate (15b). Yield: 0.283 g, 33%; light yellow liquid; [α]D25: −160.8 (c 0.20, CHCl3); IR (neat): 3419, 2361, 1731 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.74−7.72 (m, 2H), 7.55−7.53 (m, 2H), 7.34− 7.29 (m, 3H), 7.27−7.25 (m, 1H), 7.23−7.13 (m, 2H), 4.61 (s, 1H), 4.22−4.17 (m, 2H), 4.10−4.02 (m, 1H), 3.41−3.36 (m, 1H), 3.02− 2.86 (m, 2H), 2.48−2.36 (m, 2H), 2.27−2.23 (m, 2H), 1.80−1.62 (m, 4H), 1.60−1.48 (m, 4H). 1.41−1.34 (m, 4H), 1.27−1.23 (m, 3H), 0.96 (t, J = 8.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 170.4, 147.6, 146.8, 128.0, 127.8, 126.4, 125.5, 125.4, 85.7, 77.3, 76.7, 76.4, 67.6, 60.5, 50.2, 48.3, 40.6, 31.4, 29.4, 29.4, 29.1, 28.9, 28.5, 23.7, 22.6, 18.6, 14.2, 14.1; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C30H40NO3: 462.3009; found: 462.3008. 5-Phenyl-penta-3,4-dienoic Acid Ethyl Ester (10aa). Yield: 0.131 g, 65%, 99% ee; white liquid; [α]D25: −198.9 (c 0.11g, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel OB-H, hexanes:iPrOH/98:2; flow rate 0.5 mL/min, 254 nm, retention times: 17.6 min. (major) and 20.4 min. (minor); IR (neat) 1961, 1723 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.43−7.32 (m, 4H), 7.23−7.22 (m, 1H), 6.25−6.23 (m, 1H), 5.75−5.72 (m, 1H), 4.21 (quin, J = 4.0 Hz, 2H), 3.19−3.17 (m, 2H), 1.31−1.28 (m, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.3, 171.2, 133.9, 132.3, 128.6, 127.1, 95.6, 88.2, 60.9, 34.5, 14.2; HRMS (ESI-TOF) m/z: [M+NH4]+ calcd for C13H14O2 NH4: 220.1338; found: 220.1338. 5-p-Tolyl-penta-3,4-dienoic Acid Ethyl Ester (10ba). Yield: 0.146 g, 68%, 96% ee; light yellow liquid; [α]D25: −241 (c 0.5, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel OB-H, hexanes:iPrOH/98:2; flow rate 0.5 mL/min, 254 nm, retention times: 16.5 min. (minor) and 21.6 min. (major); IR (neat) 1966, 1736 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.22−7.20 (m, 1H), 7.18−7.14 (m, 2H), 7.05−7.03 (m, 1H), 6.20−6.19 (m, 1H), 5.69 (q, J = 4.0 Hz, 1H), 4.17 (quin, J = 4.0 Hz, 2H), 3.16−3.13 (m, 2H), 2.35 (s, J = 4.0 Hz, 3H), 1.32−1.1.26 (m, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.1, 171.3, 136.9, 132.4, 128.2, 129.3, 126.8, 95.4, 88.1, 60.9, 34.6, 21.2, 14.2; HRMS (ESI-TOF) m/z: [M+Na]+ calcd for C14H16O2Na: 239.1047; found: 239.1048. (R)-Ethyl-5-(m-tolyl)penta-3,4-dienoate (10ca). Yield: 0.151 g, 70%, 94% ee; yellow liquid; [α]D25: −232.4 (c 0.5 CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel AS-H, hexanes:iPrOH/100:0; flow rate 1 mL/min, 254 nm, retention times: 13.6 min. (major) and 16.1 min. (minor); IR (neat) 1965, 1720 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.25−7.22 (m, 1H), 7.21−7.18 (m, 2H), 7.14 (d, J = 4.0 Hz, 1H), 6.22−6.19 (m, 1H), 5.78 (q, J = 4.0 Hz, 1H), 4.19 (q, J = 4.0 Hz, 2H), 3.20−3.16 (m, 2H), 2.35 (s, 3H), 1.30 (t, J = 8.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.3, 171.2, 138.2, 133.8, 128.5, 127.9, 127.5, 124.0, 95.6, 88.1, 60.9, 34.6, 21.3, 14.2; HRMS (ESI-TOF): [M+Na]+ calcd for C14H16O2Na: 239.1047; found 239.1048. (R)-Ethyl 5-(4-methoxyphenyl)penta-3,4-dienoate (10da). Yield: 0.129 g, 56%, 99% ee; white liquid; [α]D25: −260.3 (c 0.4, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel ODH, hexanes:i-PrOH/95:5; flow rate 0.5 mL/min, 254 nm, retention times: 16.1 min. (major) and 19.0 min. (minor); IR (neat) 1956, 1725 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.27−7.24 (d, J = 4.0 Hz, 2H), 6.88−6.85 (d, J = 4.0 Hz, 2H), 6.20−6.18 (m, 1H), 5.70 (q, J = 4.0 Hz, 1H), 4.20 (quin, J = 4.0 Hz, 2H), 3.82 (s, 3H), 3.16 (d, J = 4.0 Hz, 2H), 1.29 (t, J = 8.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 205.7, 171.3, 158.8, 128.0, 126.1, 114.1, 95.0, 88.1, 60.9, 55.3, 34.7, 14.2; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C14H17O3: 233.1178; found: 233.1178. (R)-Ethyl 5-(3-Methoxyphenyl)penta-3,4-dienoate(10ea). Yield; 0.120g, 52%, 98% ee; white liquid; [α]D25: −255.7 (c 0.2, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantiose-

(0.020 g, 0.005 mmol), and ethylpropiolate 7a (0.108 mL, 1.0 mmol), the reaction mixture stirred for 2 h at 120 °C under N2 atmosphere. The reaction mixture cooled to room temperature. Toluene was removed using reduced pressure. Water (5 mL) and DCM (15 mL) were added. The DCM layer was washed with saturated NaCl solution, dried (Na2SO4), and concentrated. The residue was subjected to column chromatography using hexane and ethyl acetate (80:20) as eluent to isolate the 14. General Procedure for Chiral Propargylamines. To a stirred solution of amine 11 (1 mmol) in toluene (3 mL), DPPE (0.020 g, 0.005 mmol), ethyl propiolate 7a (0.108 mL, 1.0 mmol), the reaction mixture stirred for 1.5 h and then ZnI2 (0.160 g, 0.5 mmol), 1-alkyne 9a (1 mmol) at 120 °C under N2 atmosphere was added. The contents were stirred for 5 h. The reaction mixture cooled to room temperature. Toluene was removed using reduced pressure. Water (5 mL) and DCM (15 mL) were added. The DCM layer was washed with saturated NaCl solution, dried (Na2SO4), and concentrated. The residue was subjected to column chromatography using hexane and ethyl acetate (94:6) as eluent to isolate the 13. Typical Procedure for Isolation of Imine 26.4a To a stirred solution of amine 11 (1 mmol) in toluene (3 mL), DPPE (0.020 g, 0.005 mmol), ethyl propiolate 7a (0.108 mL, 1.0 mmol), the reaction mixture stirred for 1.5 h and then ZnI2 (0.160 g, 0.5 mmol), 1-alkyne 9a (1 mmol) at 120 °C under N2 atmosphere was added. T he contents were stirred for 8 h. The reaction mixture was cooled to room temperature. After removal of toluene, the residue was washed with hexane (2 × 10 mL) to dissolve the allene product. The combined hexane layers was concentrated and chromatographed on a silicagel column (100−200 mesh) to isolate the β-allenoate 10aa. The remaining residue was washed with ethyl acetate (2 × 10 mL). The combined ethyl acetate layers was filtered and concentrated under reduced pressure to obtain the imine 26. Semisolid; Yield: 0.083 g, 67%, [α]D25: −62.10 (c 0.50, CHCl3) ; IR (KBr) 3329, 1633 cm−1; 1 H NMR (400 MHz, CDCl3, δ ppm) 7.81−7.70 (m, 2H), 7.58 (s, 1H), 7.52- 7.47 (m, 2H), 7.43−7.39 (m, 2H), 7.26−7.20 (m, 4H), 5.10 (t, 1H), 4.26 (s, 1H), 2.75−2.50 (m, 2H), 1.82−1.70 (m, 2H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 179.1, 145.7, 144.2, 128.8, 126.8, 126.0, 126.3, 125.2, 125.0, 78.9, 78.3, 37.3, 20.8. (S)-Ethyl 3-(2-(Hydroxydiphenylmethyl)pyrrolidin-1-yl)acrylate (14). Yield: 0.322 g, 92%; white solid; [α]D25: −90.2 (c 0.1, CHCl3); IR (neat) 3416, 1671, 1616, 1063 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.47−7.40 (m, 1H), 7.38−7.34 (m, 5H), 7.33− 7.25 (m, 5H), 4.63−4.61 (m, 1H), 4.47−4. 44 (d, J = 8.0 Hz, 1H), 3.90−3.87 (m, 2H), 3.03 (t, J = 8.0 Hz, 2H), 2.15−1.98 (m, 3H), 1.32−1.29 (m, 2H), 1.14 (t, J = 8.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 169.3, 150.7, 144.7, 144.2, 128.3, 128.1, 127.5, 127.3, 127.0, 126.8, 86.5, 80.4, 69.2, 58.7, 49.0, 28.5, 23.0, 14.5; HRMS (ESI-TOF): [M+H]+ calcd for C22H26NO3: 352.1913; found: 352.1915. Ethyl 3-((S)-2-(Hydroxydiphenylmethyl)pyrrolidin-1-yl)-5phenylpent-4-ynoate (13). Yield: 0.226 g, 50%; light yellow liquid; [α]D25: −76.8 (c 0.13, CHCl3); IR (neat): 3418, 2356, 1730 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.81−7.82 (m, 2H), 7.62−7.53 (m, 5H), 7.43−7.38 (m, 5H), 7.34−7.29 (m, 2H), 7.24−7.16 (m, 1H), 4.35−4.15 (m, 4H), 3.78−3.68 (m, 1H), 3.14−3.0 (m, 2H), 2.68−2.53 (m, 2H), 1.89−1.77 (m, 4H), 1.36−1.26 (m, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 170.2, 147.6, 146.6, 132.4, 131.8, 130.1, 128.4, 128.3, 128.2, 128.1, 127.9, 126.6, 126.2, 125.5, 125.4, 122.9, 86.2, 85.7, 77.3, 67.9, 60.7, 60.6, 50.6, 48.6, 40.3, 29.5, 23.7, 14.3; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C30H32NO3: 454.2383; found: 454.2389. Ethyl 3-(2-(Hydroxydiphenylmethyl)pyrrolidin-1-yl)tridec-4ynoate (15a). Yield: 0.185 g, 38%; light yellow liquid; [α]D25: −165.3 (c 0.25, CHCl3); IR (neat): 3419, 2361, 1731 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.74−7.72 (m, 2H), 7.62−7.53 (m, 2H), 7.34− 7.25 (m, 3H), 7.22−15 (m, 3H), 4.21−4.17 (m, 1H), 4.08−4.07 (m, 2H), 3.39−3.32 (m, 1H), 3.08−2.91 (m, 1H), 2.45−2.41 (m, 2H), 2.27−2.24 (m, 2H), 1.68−1.60 (m, 1H), 1.58−1.53 (m, 8H), 1.49− 1.24 (m, 12H), 0.94 (t, J = 8.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 170.4, 147.6, 146.8, 128.3, 128.0, 127.9, 126.5, 126.0, 272

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

Article

The Journal of Organic Chemistry

7.01 (m, 2H), 6.22−6.20 (m, 1H), 5.76−5.71 (m, 1H), 4.23−4.17 (m, 2H), 3.18−3.17 (m, 2H), 1.35−1.28 (m, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.5, 171.0, 164.3, 163.1 (JC−F = 240 Hz), 136.4 (JC−F = 1 Hz), 131.2 (JC−F = 240 Hz), 122.6, 113.9 (JC−F = 30 Hz), 113.4 (JC−F = 20 Hz), 94.9, 88.7, 61.0, 34.3, 14.1; HRMS (ESITOF) m/z: [M+NH4]+ calcd for C13H13FO2 NH4: 238.1244; found: 238.1244. (R)-Ethyl 5-([1,1′-Biphenyl]-4-yl)penta-3,4-dienoate (10ka). Yield: 0.194, 70%; white liquid; [α]D25: −270.3 (c 1.0, CHCl3); IR (neat) 1955, 1721 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.62− 7.57 (m, 4H), 7.48−7.37 (m, 5H), 6.30−6.29 (m, 1H), 5.78 (q, J = 4.0 Hz, 1H), 4.25−4.20 (m, 2H), 3.22−3.19 (m, 2H), 1.31 (t, J = 4.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.5, 171.2, 140.7, 140.0, 133.0, 128.8, 128.7, 127.3, 127.2, 126.9, 95.3, 88.3, 60.9, 34.5, 14.2; HRMS (ESI-TOF) m/z: [M+NH4]+ calcd for C19H18O2 NH4: 296.1651; found: 296.1651. (R)-Ethyl 5-(4-Chlorophenyl)penta-3,4-dienoate (10la). Yield: 0.094, 40%; colorless liquid; [α]D25: −213.0 (c 0.75, CHCl3); IR (neat) 1955, 1725 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.33− 7.30 (m, 2H), 7.29−7.25 (m, 2H), 6.20−6.19 (m, 1H), 5.75−5.73 (m, 1H), 4.21−4.19 (m, 2H), 3.18−3.16 (m, 2H), 1.31−1.28 (m, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.4, 171.0, 132.7, 132.5, 130.0, 128.7, 128.2, 94.7, 88.6, 60.9, 34.4, 14.2; HRMS (ESI-TOF) m/ z: [M+NH4]+ calcd for C13H13ClO2NH4: 254.0948; found 254.0948. (R)-Phenethyl 5-Phenylpenta-3,4-dienoate (10ab). Yield: 0.152 g, 55%, 98% ee; white liquid; [α]D25: −220.1 (c 0.4, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel OJ-H, hexanes:iPrOH/95:5; flow rate 1 mL/min, 254 nm, retention times: 36.4 min. (major) and 33.8 min. (minor); IR (neat) 1963, 1732 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.35−7.31 (m, 6H), 7.27−7.24 (m, 4H), 6.25−6.23 (m, 1H), 5.75−5.70 (m, 1H), 4.39−4.35 (m, 2H), 3.21− 3.17 (m, 2H), 3.0−2.96 (m, 2H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.3, 171.1, 137.6, 133.9, 129.0, 128.9, 128.6, 128.5, 127.1, 126.9, 126.6, 95.6, 88.1, 65.3, 35.0, 34.4; HRMS (ESI-TOF) m/z: [M +H]+ calcd for C19H19O2: 279.1386; found: 279.1389. (R)-3-Phenylpropyl 5-Phenylpenta-3,4-dienoate (10ac). Yield: 0.175 g, 60%, 99% ee; white liquid; [α]D32: −211.6 (c 0.4 CHCl3); Rf = 0.7 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel OJ-H, hexanes:i-PrOH/90:10; flow rate 1 mL/min, 254 nm, retention times: 20.7 min. (major) and 30.4 min. (minor); IR (neat) 1963, 1732 cm−1; 1 H NMR (400 MHz, CDCl3, δppm) 7.35−7.31 (m, 6H), 7.27−7.24 (m, 4H), 6.25−6.23 (m, 1H), 5.75−5.70 (m, 1H), 4.39−4.35 (m, 2H), 3.21−3.17 (m, 2H), 3.0−2.96 (m, 2H), 2.03−1.99 (m, 2H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.3, 171.1, 137.6, 133.9, 129.0, 128.9, 128.6, 128.5, 127.1, 126.9, 126.6, 95.6, 88.2, 64.3,34.7, 32.1, 30.1; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C20H21O2: 293.1542; found: 293.1542. (R)-Pent-4-en-1-yl 5-Phenylpenta-3,4-dienoate (10ad). Yield: 0.098 g, 41%; white liquid; [α]D25: −210.3 (c 0.2, CHCl3); IR (neat) 1960, 1730, 1649 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.33− 7.22 (m, 5H), 6.24−6.23 (m, 1H), 5.84−5.72 (m, 2H), 5.07−5.02 (m, 2H), 4.16−4.14 (m, 2H), 3.20−3.17 (m, 2H), 2.16−2.14 (m, 2H), 1.78−1.75 (m, 2H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.3, 171.2, 137.3, 133.9, 132.4, 130.0, 128.6, 126.9, 115.3, 95.6, 88.2, 64.4, 34.5, 30.0, 27.7; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C16H19O2: 243.1386; found: 243.1386. Ethyl Tridec-2-en-4-ynoate (16a).15 Yield: 0.118g, 50%, white liquid; IR (neat) 2215, 1716, 1620 cm−1. 1H NMR (400 MHz, CDCl3, δppm) 6.77 (dt, J = 15.5 Hz, 2.3 Hz, 1H), 6.15 (d, J = 15.8 Hz, 1H), 4.21 (q, J = 7.1 Hz, 2H), 2.37 (td, J = 7.1, 2.2 Hz, 2H), 1.56 (quin, J = 5.5 Hz, 2H), 1.42−1.37 (m, 2H), 1.32−1.26 (m, 11H), 0.90 (t, J = 7.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 166.1, 129.2, 126.1, 100.8, 77.9, 60.5, 31.8, 29.1, 29.0, 28.8, 28.3, 22.6, 19.7, 14.2, 14.0. Ethyl Undec-2-en-4-ynoate (16b).15 Yield: 0.079g, 48%; white liquid; IR (neat) 2205, 1718, 1623 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 6.76 (d, J = 16 Hz, 1H), 6.14 (d, J = 16.0 Hz, 1H), 4.20 (q, J = 7.1 Hz, 2H), 2.39−2.35 (m, 2H), 1.60−1.50 (m, 2H), 1.44−1.26 (m,

lectivity was determined by HPLC using chiral column, chiralcel AS-H, hexanes:i-PrOH/95:5; flow rate 0.5 mL/min, 254 nm, retention times: 13.4 min. (major) and 14.8 min. (minor); IR (neat) 1961, 1726 cm−1; 1 H NMR (400 MHz, CDCl3, δppm) 7.36−7.22 (m, 1H), 6.93−6.89 (m, 2H), 6.80−6.78 (m, 1H), 6.23−6.21(m, 1H), 5.74 (q, J = 4.0 Hz, 1H), 4.24−4.218 (m, 2H), 3.85 (s, 3H), 3.19−3.17 (m, 2H), 1.31− 1.28 (m, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.4, 171.2, 159.8, 135.4, 129.5, 119.5, 112.9, 112.1, 95.6, 88.3, 60.9, 55.2, 34.5, 14.2; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C14H17O3: 233.1178; found: 233.1178. (R)- Ethyl 5-(4-(tert-Butyl)phenyl)penta-3,4-dienoate (10fa). Yield: 0.175, 68%, 90% ee; yellow liquid; [α]D25: −219.3 (c 0.40, CHCl3); Rf = 0.7 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel ODH, hexanes:i-PrOH/98:2; flow rate 0.5 mL/min, 254 nm, retention times: 16.8 min (minor) and 18.8 min (major) ; IR (neat) 1965, 1725 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.36−7.33 (m, 2H), 7.27− 7.25 (m, 2H), 6.23−6.21 (m, 1H), 5.71−5.70 (m, 1H), 4.22−4.18 (m, 2H), 3.17−3.15 (m, 2H), 1.62−1.58 (m, 3H), 1.32−1.28 (m, 9H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.2, 171.2, 150.2, 134.8, 130.9, 126.6, 125.9, 125.5, 95.2, 88.0, 60.8, 34.6, 34.5, 31.2, 14.2; HRMS (ESI-TOF) m/z: [M+H]+ calcd for C17H23O2: 259.1699; found: 259.1698. (R)-Ethyl 5-(4-Propylphenyl)penta-3,4-dienoate (10ga). Yield: 0.170, 70%, 99% ee; yellow liquid; [α]D25: −209.0 (c 0.1, CHCl3); Rf = 0.7 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel OJ-H, hexanes:i-PrOH/98:2; flow rate 0.5 mL/min, 254 nm, retention times: 18.8 min. (major) and 16.8 min. (minor); IR (neat) 1962, 1725 cm−1; 1 H NMR (400 MHz, CDCl3, δppm) 7.27−7.22 (m, 2H), 7.15−7.13 (m, 2H), 6.23−6.21 (m, 1H), 5.74−5.71 (m, 1H), 4.23−4.18 (m, 2H), 3.18−3.16 (m, 2H), 2.60−2.56 (m, 2H), 1.66−2.61 (m, 2H), 1.33− 1.28 (m, 3H), 0.95 (t, J = 4.0 Hz, 3H). 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.1, 171.3, 141.8, 132.4, 128.7, 128.3, 126.8, 95.4, 88.1, 60.9, 37.7, 34.6, 24.5, 14.2, 13.8; HRMS (ESI-TOF) m/z: [M +H]+ calcd for C16H21O2: 245.1542; found: 245.1542. (R)-Ethyl-5-(4-pentylphenyl)penta-3,4-dienoate (10ha). Yield: 0.195 g, 72%, 98% ee; yellow liquid; [α]D25: −211.7 (c 0.2, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel ODH, hexanes:i-PrOH/99:1; flow rate 0.5 mL/min, 254 nm, retention times: 11.0 min. (major) and 13.9 min. (minor); IR (neat) 1952, 1726 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.24 (d, J = 4.0 Hz, 2H), 7.14 (d, J = 4.0 Hz, 2H), 6.23−6.18 (m, 1H), 5.71 (q, J = 4.0 Hz, 1H), 4.20 (q, J = 4.0 Hz, 2H), 3.18−3.15 (m, 2H), 2.60 (t, J = 8.0 Hz, 2H), 1.58 (s, 3H), 1.33−1.27 (m, 6H), 0.91 (t, J = 4.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.1, 171.2, 142.0, 131.1, 129.9, 128.7, 126.8, 95.4, 88.0, 60.8, 35.6, 34.6, 31.4, 31.1, 14.1, 13.9; HRMS (ESI-TOF) m/z: [M+NH4]+ calcd for C18H24O2NH4: 290.2120; found: 290.2119. (R)-Ethyl 5-(4-Fluorophenyl)penta-3,4-dienoate (10ia). Yield: 0.132g, 60%, 96% ee; light yellow liquid; [α]D25: −185.4 (c 0.5, CHCl3); Rf = 0.7 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel ODH, hexanes:i-PrOH/100:0; flow rate 0.5 mL/min, 254 nm, retention times: 16.7 min. (major) and 19.6 min. (minor); IR (neat) 1954, 1736 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.31−7.27 (m, 2H), 7.04− 6.99 (m, 2H), 6.22−6.19 (m, 1H), 5.76−5.71 (m, 1H), 4.23−4.21 (m, 2H), 3.19−3.16 (m, 2H), 1.30 (t, J = 4.0 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 206.1, 171.1, 163.2, 160.8, 132.4, 130.0, 129.8, 128.3, 115.6, 115.4, 94.6, 88.5, 60.9, 34.5, 14.2; HRMS (ESITOF) m/z: [M+NH4]+ calcd for C13H13FO2 NH4: 238.1244; found: 238.1242. (R)-Ethyl 5-(3-Fluorophenyl)penta-3,4-dienoate (10ja). Yield: 0.129g, 59%, 99% ee; light yellow liquid; [α]D25: −193.9 (c 0.5, CHCl3); Rf = 0.6 (silica gel, hexane/EtOAc 95:5); The enantioselectivity was determined by HPLC using chiral column, chiralcel OBH, hexanes:i-PrOH/98:2; flow rate 1.0 mL/min, 254 nm, retention times: 23.6 min. (major) and 18.8 min. (minor); IR (neat) 1956, 1736 cm−1; 1H NMR (400 MHz, CDCl3, δppm) 7.30−7.29 (m, 2H), 7.03− 273

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274

Article

The Journal of Organic Chemistry 13H), 0.89 (t, J = 7.1 Hz, 3H); 13C{1H}NMR (100 MHz, CDCl3, δppm) 166.1, 129.2, 126.1, 100.8, 77.9, 60.5, 31.2, 28.5, 28.2, 22.5, 19.7, 14.2, 14.0.

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(7) (a) Cai, F.; Pu, X.; Qi, X.; Lynch, V.; Radha, A.; Ready, J. M. J. Am. Chem. Soc. 2011, 133, 18066. (b) Pu, X.; Qi, X.; Ready, J. M. J. Am. Chem. Soc. 2009, 131, 10364. (c) Löhr, S.; Averbeck, J.; Schürmann, M.; Krause, N. Eur. J. Inorg. Chem. 2008, 2008, 552. (d) Sato, I.; Matsueda, Y.; Kadowaki, K.; Yonekubo, S.; Shibata, T.; Soai, K. Helv. Chim. Acta 2002, 85, 3383. (8) (a) Widenhoefer, R. A.; Zhang, Z. Angew. Chem., Int. Ed. 2007, 46, 283. (b) Liu, L.; Xu, Bo.; Mashuta, M. S.; Hammond, G. B. J. Am. Chem. Soc. 2008, 130, 17642. (c) Shi, Y.; Roth, K. E.; Ramgren, S. D.; Blum, S. A. J. Am. Chem. Soc. 2009, 131, 18022. (d) Kalek, M.; Fu, G. C. J. Am. Chem. Soc. 2015, 137, 9438. (9) (a) Haubrich, A.; van Klaveren, M.; van Koten, G.; Handke, G.; Krause, N. J. Org. Chem. 1993, 58, 5849. (b) Henderson, M. A.; Heathcock, C. H. J. Org. Chem. 1988, 53, 4736. (c) Krause, N.; Handke, G. Tetrahedron Lett. 1991, 32 (49), 7229. (d) Tang, Y.; Shen, L.; Dellaria, B. J.; Hsung, R. P. Tetrahedron Lett. 2008, 49, 6404. (10) Wang, M.; Liu, Z. L.; Zhang, X.; Tian, P. P.; Xu, Y. H.; Loh, T. P. J. Am. Chem. Soc. 2015, 137, 14830. (11) (a) Sriramurthy, V.; Barcan, B. A.; Kwon, O. J. Am. Chem. Soc. 2007, 129, 12928. (b) Sriramurthy, V.; Kwon, O. Org. Lett. 2010, 12, 1084. (c) Wolf, C.; Xu, H. Chem. Commun. 2011, 47, 3339. (12) (a) Lowe, G. J. Chem. Commun. 1965, 411. (b) Brewster, J. H. Top. Stereochem. 1967, 2, 1. (13) (a) Fife, T. H.; Hagopian, L. J. Am. Chem. Soc. 1968, 90, 1007. (b) Fife, T. H.; Hutchins, J. E. C. J. Org. Chem. 1980, 45, 2099. (14) (a) Crabbé, P.; Fillion, H.; André, D.; Luche, J.-L. J. Chem. Soc., Chem. Commun. 1979, 859. (b) Searles, S.; Li, Y.; Nassim, B.; Lopes, M.-T. R.; Tran, P. T.; Crabbé, P. J. Chem. Soc., Perkin Trans. 1 1984, 747. (c) Lo, V. K. Y.; Wong, M. K.; Che, C. M. Org. Lett. 2008, 10, 517. (d) Kuang, J.; Ma, S. J. Am. Chem. Soc. 2010, 132, 1786. (e) Tang, X.; Zhu, C.; Cao, T.; Kuang, J.; Lin, W.; Ni, S.; Ma, S.; Zhang, J. Nat. Commun. 2013, 4, 2450. (15) Bedke, D. K.; Shibuya, G. M.; Pereira, A. R.; Gerwick, W. H.; Vanderwal, C. D. J. Am. Chem. Soc. 2010, 132, 2542.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b02632. ORTEP of compound 14 and HPLC and 1H/13C NMR spectra (PDF) X-ray crystallographic data for compound 14 (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Mariappan Periasamy: 0000-0001-6376-6589 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are thankful to the DST-SERB (New Delhi) for a J.C. Bose National Fellowship (SR/S2/JCB-33/2005) and Green Chemistry (SB/S5/GC-01/2014) research grants and also to the CSIR, New Delhi, for a research grant (02/0176/14/EMR-II). Support of the UGC under UPE and CAS programs is also gratefully acknowledged. L.M., I.S., and P.O.R. are thankful to the UGC and CSIR (New Delhi) for research fellowships.

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REFERENCES

(1) (a) Neff, R. K.; Frantz, D. E. ACS Catal. 2014, 4, 519. (b) RiveraFuentes, P.; Diederich, F. Angew. Chem., Int. Ed. 2012, 51, 2818. (c) Jin, J.; Weinreb, S. M. J. Am. Chem. Soc. 1997, 119, 2050. (d) Wan, Z.; Nelson, S. G. J. Am. Chem. Soc. 2000, 122, 10470. (e) Crimmins, M. T.; Emmitte, K. A. J. Am. Chem. Soc. 2001, 123, 1533. (2) (a) Chu, W. D.; Zhang, Y.; Wang, J. Catal. Sci. Technol. 2017, 7, 4570. (b) Mundal, D. A.; Lutz, K. E.; Thomson, R. J. J. Am. Chem. Soc. 2012, 134, 5782. (c) Hassink, M.; Liu, X.; Fox, J. M. Org. Lett. 2011, 13, 2388. (d) Lim, J.; Choi, J.; Kim, H.-S.; Kim, I. S.; Nam, K. C.; Kim, J.; Lee, S. J. Org. Chem. 2016, 81, 303. (3) (a) Hoffmann-Röder, A.; Krause, N. Angew. Chem., Int. Ed. 2004, 43, 1196. (4) (a) Periasamy, M.; Sanjeevakumar, N.; Dalai, M.; Gurubrahamam, R.; Reddy, P. O. Org. Lett. 2012, 14, 2932. (b) Gurubrahamam, R.; Periasamy, M. J. Org. Chem. 2013, 78, 1463. (c) Periasamy, M.; Reddy, P. O.; Sanjeevakumar, N. Tetrahedron: Asymmetry 2014, 25, 1634. (d) Periasamy, M.; Reddy, P. O.; Sanjeevakumar, N. Eur. J. Org. Chem. 2013, 2013, 3866. (e) Periasamy, M.; Reddy, P. O.; Satyanarayana, I.; Mohan, L.; Edukondalu, A. J. Org. Chem. 2016, 81, 987. (f) Poh, J. S.; Makai, S.; von Keutz, T.; Tran, D. N.; Battilocchio, C.; Pasau, P.; Ley, S. V. Angew. Chem., Int. Ed. 2017, 56, 1864. (5) (a) Tang, Y.; Chen, Q.; Liu, X.; Wang, G.; Lin, L.; Feng, X. Angew. Chem., Int. Ed. 2015, 54, 9512. (b) Suarez, A.; Fu, G. C. Angew. Chem., Int. Ed. 2004, 43, 3580. (c) Hassink, M.; Liu, X.; Fox, J. M. Org. Lett. 2011, 13, 2388. (d) Xiao, Q.; Xia, Y.; Li, H.; Zhang, Y.; Wang, J. Angew. Chem., Int. Ed. 2011, 50, 1114. (6) (a) Crouch, I. T.; Neff, R. K.; Frantz, D. E. J. Am. Chem. Soc. 2013, 135, 4970. (b) Lee, P.; Mo, J.; Kang, D.; Eom, D.; Park, C.; Lee, C. H.; Jung, Y. M.; Hwang, H. J. Org. Chem. 2011, 76, 312. (c) Liu, H.; Leow, D.; Huang, K. W.; Tan, C. H. J. Am. Chem. Soc. 2009, 131, 7212. (d) Qian, H.; Yu, X.; Zhang, J.; Sun, J. J. Am. Chem. Soc. 2013, 135, 18020. (e) Akpinar, G. E.; Kus, M.; Ucuncu, M.; Karakus, E.; Artok, L. Org. Lett. 2011, 13, 748. 274

DOI: 10.1021/acs.joc.7b02632 J. Org. Chem. 2018, 83, 267−274