DBU-Promoted Cascade Annulation of Nitroarylcyclopropane-1,1

Nov 7, 2018 - ... An Access to Highly Functionalized Cyclopenta[b]furan Derivatives ... College of Basic Medicine, Jining Medical University , Jining ...
0 downloads 0 Views 956KB Size
Download PDF
Note pubs.acs.org/joc

Cite This: J. Org. Chem. 2018, 83, 14768−14776

DBU-Promoted Cascade Annulation of Nitroarylcyclopropane-1,1dicarbonitriles and 3‑Aryl-2-cyanoacrylates: An Access to Highly Functionalized Cyclopenta[b]furan Derivatives Siran Qian,†,§ Zengyang Xie,‡,§ Jiaming Liu,† Mingshuang Li,† Shan Wang,† Naili Luo,† and Cunde Wang*,† †

School of Chemistry and Chemical Engineering, Yangzhou University, 180 Siwangting Street, Yangzhou 225002, P. R. China College of Basic Medicine, Jining Medical University, Jining 272067, P. R. China

J. Org. Chem. 2018.83:14768-14776. Downloaded from pubs.acs.org by UNIV OF SOUTH DAKOTA on 12/18/18. For personal use only.

‡

S Supporting Information *

ABSTRACT: A DBU-promoted cascade annulation of nitroarylcyclopropane-1,1-dicarbonitriles and 3-aryl-2-cyanoacrylates for the synthesis of highly functionalized cyclopenta[b]furan derivatives is described. High stereoselectivity, fused cyclopentane and furan can be established in a single reaction, highlighting the high efficiency and step-economy of this protocol. This reaction offers a novel and straightforward protocol to the synthesis of cyclopenta[b]furans featuring the [3 + 2] cycloadditions of nitroarylcyclopropane-1,1-dicarbonitriles with 3-aryl-2-cyanoacrylates. from our research group in this field, a new [3 + 3] annulation reaction of 2-aroyl-3-arylcyclopropane-1,1-dicarbonitriles was disclosed for the synthesis of fully substituted benzenes.5c The following fully substituted anilines also were successfully prepared via [4 + 2] annulation of 2-aroyl-3-arylcyclopropane-1,1-dicarbonitriles with 3-aryl-2-cyanoacrylate mediated by DBU.7 However, when we further explored the generality of this reaction with a variety of 2-aroyl-3-nitrophenylcyclopropane−1,1-dicarbonitriles to the reaction conditions, quite unexpectedly, the corresponding fully substituted anilines were not obtained, and the fused cyclopenta[b]furan-6carboxylates were yielded with complete relative stereoselectivity via simple DBU-mediated twice annulations. The pleasing result promoted us to improve further the reaction conditions for the construction of the cyclopenta[b]furan core. Functionalized cyclopenta[b]furans are important structural motifs of numerous biologically active natural products and synthetic pharmaceuticals (Figure 1).8−11 For example, (−)-rocaglamide (Scheme 1) is a potent inhibitor of P388 lymphocytic leukemia, a novel natural product isolated from Aglaiaelliptifolia Merr.8−11 The cyclopenta[b]furan class of natural products also includes more complex polycyclic compounds incorporating further fused saturated or unsaturated rings. For instance, the marine alkaloid nakadomarin A9 contains a reduced pyridine and pyrrole core structure, whereas sessilifoliamide I10 can be seen as Stemona derived alkaloids, and the brazilide A11 is characterized by core structures derived from furan-fused cyclopentanones and chromane, as well as the euphane

D

onor−acceptor cyclopropanes (D−A cyclopropanes) have emerged as important synthons for the construction of complex architectures in organic chemistry due to their stereoelectronic factors and intrinsic ring strain.1 D−A cyclopropanes generate easily the stabilized dipoles which can participate in a variety of the annulations and cycloadditions with nucleophiles and electrophiles to these cyclic compounds.2 Moreover, for quite some time the annulations and cycloadditions of D−A cyclopropanes with all-carbon partners have proved to be powerfully synthetic tools to form carbocyclic compounds. In this light, D−A cyclopropanes have emerged to have a prominent role, in recent years remarkable progress has been acquired which led to the development of highly substituted five-membered carbocycles synthesis, based on the [3 + 2] annulation of functionalized D−A cyclopropanes with alkenes, alkynes, allenes, enol ethers, and enamines.3 As a new type of D−A cyclopropane with threecarbon building blocks, these 1-cyanocyclopropane-1-carboxylate derivatives were used widely in the construction of heterocycles and carbocycles. Because of the synergistic effects of the strain and high polarization of the ring, the cyclopropane ring may be cleaved into two 1,3-dipoles in various conditions for the preparation of very important molecular scaffolds, providing a method that was diversity oriented.4 Recently, we have demonstrated the utility of the base-mediated opening ring of 1-cyanocyclopropane-1-carboxylates for the synthesis of densely functionalized and architecturally complex compounds.5 Like 1-cyanocyclopropane-1-carboxylates, 2-aroyl-3arylcyclopropane-1,1-dicarbonitriles as appropriate D−A cyclopropane candidates can also participate as dipoles in a variety of cycloaddition reactions via rapid ring opening under appropriate conditions.6 As a result of continuing efforts © 2018 American Chemical Society

Received: September 8, 2018 Published: November 7, 2018 14768

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry

Figure 1. Examples for cyclopenta[b]furan containing natural product and synthetic pharmaceuticals.

synthetic strategies to this cyclopenta[b]furan moiety have been researched, to the best of our knowledge, no example of this kind of base-promoted [3 + 2]/[3 + 2] cycloaddition reaction has been reported. At the outset of our experiment, the reaction between 1a and 2a in the mole ratio 1.0:1.0 was chosen as the model reaction (Table 1). First, the solution of substrates 1a and 2a

Scheme 1. Proposed Reaction Mechanism

Table 1. Screening of Reaction Conditions for the Synthesis of 3a

triterpenes fused cyclopenta[b]furan core12 are a new class of natural products from Lantana Camara, and their simplified synthetic compounds including cyclopenta[b]furan core are used as potential inhibitors to treat thrombotic disorders.13 Synthetic GRL-06579A (Figure 1) is considered to be a powerful enzyme inhibitor and antiviral agent for treatment of HIV.14 Additionally, Strigolactones core structures derived from fused cyclopentanfuran are important plant hormones, involved in several crucial processes like seed germination, plant growth, and shoot branching.15 Therefore, efficient synthesis methods for cyclopenta[b]furan system should be of great importance. In spite of the importance of the cyclopenta[b]furans, only a few methods were reported for the synthesis of these cyclopenta[b]furan derivatives. The existing methods include oxidative cyclization of o-cyclopentenylphenol derivatives,8b [2 + 2] cycloaddition oxidation sequence,16 iodine-catalyzed reaction of indandione/indanone and aldehydes,17 hypervalent-iodine-mediated direct dehydrogenative α,β′-bifunctionalization of β-ketoesters and β-diketones,18 lactonization of 2substituted indanone,19 triphenylphosphine-mediated annulation from dialkyl acetylenedicarboxylates,20 Nazarov reactions of 2-furyl vinyl ketones and related enones,21 cobalt-catalyzed domino reaction between 2-bromoaryl aldehyde and dimethyl itaconate,22 ring-closing metathesis/atom-transfer ring closure strategy,23 acid-catalyzed double cyclization,24 and intramolecular carboxypalladation of alkynoic acids followed by intramolecular olefin insertion.25 Recently, Vitale and coworkers reported that few compounds containing cyclopenta[b]furan moiety were prepared through formal [3 + 2] cycloadditions of 2-nitrobenzofurans with vinylcyclopropanes in the presence of palladium(0) catalyst.26 Despite several

a

entry

base (equiv)

solvent

T (°C)

t (h)

yield (%)a

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 14b 15b

(−) Et3N (1.0) Et3N (1.0) piperidine (1.0) DBU (1.0) DABCO (1.0) K2CO3 (1.0) NaOH (1.0) DBU (1.0) DBU (1.0) DBU (1.0) DBU (1.0) DBU (1.0) DBU (1.25) DBU (0.75) EtONa (1.0) guanidine (1.0)

DCM DCM DCM DCM DCM DCM DCM DCM 1,2-DCE THF toluene EtOH DMF DCM DCM toluene DCM

20 20 40 40 40 40 40 40 80 70 110 80 100 40 40 40 40

24 24 24 24 12 14 12 12 14 14 14 16 24 10 14 12 12

0 0 25 11 89 69 trace trace 82 72 78 65 trace 89 83 36 88

Isolated yields. bNitrogen atmosphere and dried solvent.

in dichloromethane was stirred at 20 °C without any promoter for 24 h, and the conceivable annulation product was not obtained (Table 1, entry 1). Then when the experiment was performed with the reaction between 1a and 2a using 1 equiv Et3N as a basic promoter at 20 °C for 24 h (Table 1, entry 2), no annulation product was observed. Under otherwise identical conditions, the annulation product 3a was obtained in 25% yield when the reaction was carried out at 40 °C (Table 1, entry 3). The following various bases, piperidine, DBU, DABCO, K2CO3, and NaOH, were employed, respectively, for basic promoters evaluation (entries 4−8). It seems that more basic organic amines were beneficial to the reaction. With the use of DBU and DABCO as the catalyst, the reaction worked at 40 °C for 12 or 14 h to give the product 3a in 89% and 69% yield (entries 5−6), respectively. Compared with Et3N, DBU 14769

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry displayed much better catalytic activity, greatly shortening the reaction time to 12 h to afford the product 3a (entry 5). With the use of inorganic amines such as K2CO3 or NaOH instead of amines as the basic promoter, only a trace product was observed under otherwise identical conditions (entries 7−8). In an attempt to improve yield, different solvents were employed to escalate the reaction temperature. When 1,2DCE, THF, toluene, or EtOH were used, respectively, in the reaction at different reaction temperatures, the product 3a was obtained in good yields (entries 9−12); however, with the use of DMF as the solvent, the reaction worked at 100 °C to give only the trace product 3a even when the reaction time was prolonged for 24 h (entry 13), the results support the important role that the solvent and the reaction temperature may play in the transition state of this opening ring of D−A cyclopropanes, the higher temperature, and the polar aprotic solvents were propitious to the formation of the product 3a. Increasing the DBU loading to 1.25 equiv did not have a significant improvement under otherwise identical conditions (entry 14). Lowering the DBU loading to 0.75 equiv still resulted in 3a in 83% yield, albeit requiring a reaction time of 14 h (entry 15). Additionally, the organic bases EtONa and guanidine were used in the cascade [3 + 2]/[3 + 2] cycloaddition under nitrogen atmosphere in dried toluene and dichloromethane, respectively (entries 16−17), and a modest 36% yield of 3a was obtained with 1 equiv of EtONa in dried toluene (entry 16); EtONa performed worse than the bases DBU and DABCO studied due to both its nucleophilic ability to carry on conjugate addition more readily with acrylates.27 Guanidine (1 equiv) gave a 88% yield of 3a in dried DCM under nitrogen (entry 17), which promoted to catalyze the reaction similarly to DBU. The best result was obtained in the mole ratio 1.0:1.0 for 1a/2a using DBU (1.0 equiv) as the base at 40 °C in dichloromethane under reflux for 12 h, whereby the yield of product 3a reached 89% (Table 1, entry 5). After the optimal conditions were determined, various nitrophenylcyclopropanes 1a−f and acrylates 2a−i with different substituents were carefully investigated (Table 2). The results indicated that D−A cyclopropanes 1a−f and acrylates 2a−i bearing electron-withdrawing substituents or electron-donating substituents on the aromatic ring are suitable substrates, and the corresponding 3a−r were obtained with usually good to high yields. Substrate acrylates 2a−i at aromatic ring bearing chloro, bromo, methoxy, or methyl did not have a remarkable influence on the reaction. Additionally, the substrate acrylates 2a−i with a heterocyclic core such as thiophene were also compatible substrates under the optimal reaction conditions, and the corresponding product was obtained in excellent yield (Table 2, entry 13). Both electron-donating and electron-withdrawing substituents on the aromatic aroyl group of D−A cyclopropanes 1a−f were well tolerated. The results revealed that a significant ortho site effect of the nitro group was observed. For example, the 2-nitro substituted on the nitrobenzene led to lower yields of the products compared with their 4-substituted counterparts even though the reaction time was prolonged to 16 h. However, the 3-nitro substituted on the nitrobenzene did not undergo annulation under the optimal reaction conditions. Meanwhile, when other electron-withdrawing groups such as p-CF3, mnitro were used to replace the ortho- or para-nitro group of D− A cyclopropanes 1a−f, the reaction did not work either via cascade annulations, and it only gave the corresponding aniline

Table 2. Synthesis of 6,6a-Dihydro-5H-cyclopenta[b]furan6-carboxylatesa

entry

R1

R2

R3

yield (%)b

1 2 3 4 5 6 7 8 9 10 11 12 13c,d 14c 15 16 17c 18c

p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 p-NO2 o-NO2 o-NO2

m-CH3O p-CH3O p-CH3O m-CH3O p-CH3O p-CH3O m-Cl p-CH3O m-CH3 m-CH3O m-CH3 m-CH3O m-CH3O p-CH3O p-Br m-CH3O p-CH3O p-CH3O

p-CH3 p-CH3 p-Br p-Cl p-Cl m-CH3 p-OCH3 p-CH3O m-CH3O p-Br p-CH3O 3,4-OCH2CH2O thiophen-2-yl m-Cl p-CH3 m-CH3 p-Br p-Cl

89(3a) 89(3b) 87(3c) 88(3d) 88(3e) 89(3f) 89(3g) 87(3h) 90(3i) 90(3j) 91(3k) 88(3l) 89(3m) 84(3n) 86(3o) 89(3p) 85(3q) 83(3r)

a

Reaction conditions: D−A cyclopropanes 1a-f (1 mmol), acrylates 2a-i (1 mmol), DBU (152 mg, 1 mmol), DCM (15 mL), 40 °C, 12 h. b Isolated yield cReaction time: 16 h. dUsing ethyl 2-cyano-3(thiophen-2-yl)acrylate as a substrate.

derivates (see Supporting Information).7 The relative configuration of 3h and 3p bearing an amine and a carboxylate contiguous substituents at C(2) and C(6), two cyano substituents at C(3) and C(6), three aryl contiguous substituents at C(4), C(5), and C(6a) of 5H-cyclopenta[b]furan core was determined by X-ray crystallography (Figure 2).28 On the basis of the above-described results and our previous work on organic base-mediated opening-ring/closing-ring reactions of D−A cyclopropane compounds, we propose the mechanism outlined in Scheme 1. First, DBU-mediated deprotonation of D−A cyclopropane affords a cyclopropan-1ide [A], which undergoes opening ring to produce prop-2-en1-ide [B].5a In view of nitro group as a strong electronwithdrawing group of prop-2-en-1-ide [B], in addition to induced effects, ortho or para-nitro group promotes the charge separation of anion [B] by conjugation effects. Chargeseparated resonance structures do contribute very much to stabilize anion [B] via the resonance hybrids anion [C], [D], and [E]. The Micheal addition of substituted benzyl anion [C] to the double bond of the substrate acrylate gave the adduct [F]. Subsequently, the intramolecular nucleophilic addition of intermediate [F] to C2-carbonyl group of aroyl forms the intermediate nitrophenylcyclopentan-1-olate, following the addition to C5-cyano group transfers easily to the dicyclo intermediate [G] again.5b,f The 2-amino-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylates 3a−r are finally obtained through 1,5-H shift of the intermediate [G] in the presence of 14770

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry

Figure 2. Molecular structures of 3h and 3p, non-hydrogen atoms are shown at the 30% probability level. chromatography (TLC). For TLC, silica gel plates (HSGF 254) were used, and compounds were visualized by irradiation with UV light. Flash column chromatography was performed using silica gel (230−400 mesh). Acrylates 2a−i and other reagents were purchased from commercial suppliers and purified by standard techniques. Procedure for Preparation of Nitrophenylcyclopropanes 1a−f. The nitrophenylcyclopropanes 1a−f were synthesized following a literature procedure method as described.29 (2S,3R/2R,3S)-2-(3-Methoxybenzoyl)-3-(4-nitrophenyl)cyclopropane-1,1-dicarbonitrile (1a). Bright yellow solid, 812 mg, yield: 78%; mp 195.5−196.0 °C (EA/PE); IR (KBr, cm−1): 3440, 2972, 2930, 2730, 2672, 2431, 2202, 1680, 1550, 1436, 1332, 1267, 1107, 1021; 1H NMR (600 MHz, DMSO-d6) δ (ppm): 8.30 (d, J = 8.4 Hz, 2H), 8.02 (d, J = 8.4 Hz, 2H), 7.91 (d, J = 7.2 Hz, 1H), 7.76 (s, 1H), 7.56 (dd, J = 8.4 and 7.2 Hz, 1H), 7.36 (d, J = 7.8 Hz, 1H), 5.20 (d, J = 8.4 Hz, 1H), 4.27 (d, J = 8.4 Hz, 1H), 3.88 (s, 3H); 13 C{1H} NMR (150 MHz, DMSO-d6) δ (ppm): 189.7, 159.6, 147.8, 138.2, 136.6, 130.7, 130.2, 123.5, 121.7, 120.8, 113.6, 112.5, 112.4, 55.6, 37.5, 34.8, 15.6; HR-MS (ESI) calcd for C19H13N3NaO4 [(M + Na)+]: 370.0804; Found: 370.0802. (2S,3R/2R,3S)-2-(4-Methoxybenzoyl)-3-(4-nitrophenyl)cyclopropane-1,1-dicarbonitrile (1b). Bright yellow solid, 844 mg, yield: 81%; mp 211.5−212.0 °C (EA/PE); IR (KBr, cm−1): 3432, 2980, 2932, 2730, 2672, 2422, 2209, 1686, 1552, 1450, 1332, 1289, 1092, 1008; 1H NMR (600 MHz, DMSO-d6) δ (ppm): 8.30 (d, J = 7.8 Hz, 2H), 8.29 (d, J = 8.4 Hz, 2H), 8.01 (d, J = 9.0 Hz, 2H), 7.17 (d, J = 9.0 Hz, 2H), 5.16 (d, J = 8.4 Hz, 1H), 4.25 (d, J = 8.4 Hz, 1H), 3.91 (s, 3H); 13C{1H} NMR (150 MHz, DMSO-d6) δ (ppm): 187.8, 164.5, 147.8, 138.3, 131.8, 130.7, 128.2, 123.5, 114.3, 112.6, 112.5, 55.8, 37.2, 34.5, 15.3; HR-MS (ESI) calcd for C19H13N3NaO4 [(M + Na)+]: 370.0804; Found: 370.0794. (2S,3R/2R,3S)-2-(3-Chlorobenzoyl)-3-(4-nitrophenyl)cyclopropane-1,1-dicarbonitrile (1c). Bright yellow solid, 876 mg, yield: 83%; mp 216.5−217.5 °C (EA/PE); IR (KBr, cm−1): 3428, 3130, 2980, 2922, 2730, 2674, 2426, 2221, 1682, 1555, 1438, 1330, 1270, 1096, 1001; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.43 (s, 1H), 8.30 (d, J = 8.0 Hz, 2H), 8.20 (d, J = 8.0 Hz, 1H), 8.02 (d, J = 8.0 Hz, 2H), 7.84 (d, J = 7.6 Hz, 1H), 7.67 (t, J = 7.6 Hz, 1H), 5.21 (d, J = 8.0 Hz, 1H), 4.25 (d, J = 8.0 Hz, 1H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 189.7, 148.3, 138.7, 137.7, 134.7, 134.4, 131.3, 131.2, 129.6, 128.1, 123.9, 113.0, 112.1, 38.2, 34.8, 16.7; HRMS (ESI) calcd for C18H10ClN3NaO3 [(M + Na)+]: 374.0308; Found: 374.0302. (2S,3R/2R,3S)-2-(3-Methylbenzoyl)-3-(4-nitrophenyl)cyclopropane-1,1-dicarbonitrile (1d). Bright yellow solid, 756 mg, yield: 76%; mp 149.0−149.5 °C (EA/PE); IR (KBr, cm−1): 3420, 3132, 2980, 2920, 2734, 2670, 2420, 2220, 1679, 1550, 1440, 1332, 1272, 1090, 898; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.73 (s, 1H), 8.43 (d, J = 8.0 Hz, 2H), 8.31 (d, J = 8.0 Hz, 1H), 8.14 (d, J = 7.6 Hz, 1H), 8.03 (d, J = 8.0 Hz, 2H), 7.57 (t, J = 7.6 Hz, 1H), 5.18

base DBU. Moreover, the above reactions are carried out under the optimized reaction conditions when the ortho or para-nitro group of D−A cyclopropanes is replaced by other analogously electron-withdrawing groups such as p-CF3 and mnitro. The reactions do not afford the title cascade annulations and only gave the corresponding aniline derivates via [4 + 2] annulations promoted by DBU (see Supporting Information).7 Additionally, to understand further the proposed mechanism, the nitroarylcyclopropane-1,1-dicarbonitrile was replaced with 1-cyanocyclopropane-carbonate for the reaction with 3-aryl-2cyanoacrylate, and the result showed that the reaction of 1cyanocyclopropanecarbonate and 3-aryl-2-cyanoacrylate afforded the simple [3 + 2] cycloaddition to yield a highly functionalized cyclopentane (see Supporting Information). According to the experimental results, the strongly electronwithdrawing ortho or para-nitro group of D−A cyclopropanes plays a very crucial role in the title reactions by synergetic conjugation effects and induced effects. In summary, we have demonstrated that a range of fused cyclopenta[b]furan-6-carboxylates can be successfully obtained with complete relative stereoselectivity via a simple DBUmediated cascade annulation of D−A nitroarylcyclopropane and 3-aryl-2-cyanoacrylates. The reaction is simply promoted by DBU giving the final products in good yields via domino sequence, including ring opening of D−A nitroarylcyclopropane, regioselective Micheal addition, twice intramolecular nucleophilic addition, and 1,5-H shift. The developed procedure offers several advantages, including good yields, operational simplicity, mild reaction conditions, and easily available substrates D−A nitroarylcyclopropanes and 3-aryl-2cyanoacrylate, which makes it a useful practical process for the synthesis of these cyclopenta[b]furan-6-carboxylate derivatives.

■

EXPERIMENTAL SECTION

Melting points were measured on a Mel-Tem capillary melting point apparatus and are uncorrected. 1H NMR spectra are recorded at 400 or 600 MHz, and 13C NMR were recorded at 100 or 150 MHz in DMSO-d6 referenced to TMS. 1H NMR data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, br = broad, m = multiplet), coupling constants (Hz), and integration. Chemical shifts are reported in parts per million relative to TMS (1H, δ 0.00; 13C, δ 0.00). High-resolution mass spectra analysis was performed using electrospray ionization (ESI) and a TOF analyzer. IR spectra were reported in frequency of absorption (cm−1) with KBr pellet. All reactions were monitored by thin layer 14771

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry (d, J = 8.0 Hz, 1H), 4.27 (d, J = 8.0 Hz, 1H), 2.45 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 193.1, 138.3, 137.0, 134.2, 132.9, 130.0, 129.9, 129.1, 128.7, 126.8, 117.9, 112.9,112.1, 32.5, 31.3, 21.4, 16.1; HR-MS (ESI) calcd for C19H13N3NaO3 [(M + Na)+]: 354.0855; Found: 354.0851. (2 S,3R/2R,3S)-2-(4-Bromobenzoyl)-3-(4-nitrophenyl)cyclopropane-1,1-dicarbonitrile (1e). Bright yellow solid, 975 mg, yield: 82%; mp 247.2−247.0 °C (EA/PE); IR (KBr, cm−1): 3430, 2977, 2930, 2728, 2676, 2425, 2202, 1680, 1550, 1442, 1330, 1287, 1082, 998; 1H NMR (600 MHz, DMSO-d6) δ (ppm): 8.30 (d, J = 8.4 Hz, 2H), 8.23 (d, J = 8.4 Hz, 2H), 8.01 (d, J = 9.0 Hz, 2H), 7.87 (d, J = 9.0 Hz, 2H), 5.17 (d, J = 8.4 Hz, 1H), 4.26 (d, J = 8.4 Hz, 1H); 13 C{1H} NMR (150 MHz, DMSO-d6) δ (ppm): 189.4, 147.8, 138.3, 134.5, 132.0, 131.1, 130.7, 129.1, 123.4, 112.5, 112.4, 37.6, 34.5, 15.9; HR-MS (ESI) calcd for C18H10BrN3NaO3 [(M + Na)+]: 417.9803; Found: 417.9801. (2S,3R/2R,3S)-2-(4-Methoxybenzoyl)-3-(2-nitrophenyl)cyclopropane-1,1-dicarbonitrile (1f). Bright yellow solid, 761 mg, yield: 73%; mp 210.3-211.3 °C (EA/PE); IR (KBr, cm−1): 3387, 2976, 2920, 2720, 2670, 2426, 2220, 1675, 1532, 1450, 1311, 1265, 1090, 898; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.30 (d, J = 7.2 Hz, 2H), 8.28 (t, J = 8.4 Hz, 1H), 7.89 (d, J = 6.6 Hz, 2H), 7.78−7.76 (m, 1H), 7.17 (d, J = 9.0 Hz, 2H), 5.13 (d, J = 8.4 Hz, 1H), 4.27 (d, J = 8.4 Hz, 1H), 3.91 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 187.9, 164.5, 148.9, 134.4, 131.9, 131.8, 130.9, 128.3, 126.3, 125.5, 114.3, 112.9, 112.7, 55.8, 36.6, 35.0, 15.5; HR-MS (ESI) calcd for C19H13N3NaO4 [(M + Na)+]: 370.0804; Found: 370.0801. General Procedure for Preparation of 4-Nitrophenyl-6,6adihydro-5H-cyclopenta[b]furan-6-carboxylate (3a−r). To the mixture of nitrophenylcyclopropanes 1a−f (1.0 mmol) and ethyl 2cyano-3-phenylacrylates 2a−i (1.0 mmol) in dichloromethane (15 mL) was added DBU (152 mg, 1.0 mmol), and the resulting mixture was slowly warmed up to 40 °C and stirred sequentially for ca. 12 h until full conversion of the nitrophenylcyclopropanes was achieved (monitored by TLC, Hexanes/EtOAc, 3/1). Upon completion, the reaction mixture was diluted with 10 mL of H2O and extracted with dichloromethane (10 mL × 2). The combined organic layers were washed with water (10 mL) and brine (10 mL), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to yield a crude product. The crude product was purified by column chromatography (EtOAc/hexanes, 1/5, silica gel) to provide the desired products 3a−r. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-6a-(3-methoxyphenyl)-4-(4-nitrophenyl)-5-(p-tolyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3a). Bright yellow solid, 501 mg, yield: 89%; mp 202.2−203.2 °C (EA/PE); IR (KBr, cm−1): 3410, 3320, 3170, 2999, 2206, 1554, 1513, 1442, 1337, 1237, 1109, 1023, 896, 786; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.19 (s, 2H), 8.10 (d, J = 8.1 Hz, 2H), 7.55 (d, J = 8.1 Hz, 2H), 7.43 (dd, J = 7.6 Hz, 1H), 7.07 (d, J = 6.1 Hz, 3H), 7.05−6.94 (m, 3H), 6.89 (s, 1H), 5.49 (s, 1H), 3.98 (s, 2H), 3.77 (s, 3H), 2.20 (s, 3H), 1.07 (t, J = 6.7 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.3, 163.3, 159.8, 145.5, 142.9, 141.6, 137.8, 135.4, 132.7, 130.6, 129.1, 129.0, 123.6, 118.2, 116.0, 115.8, 115.2, 115.0, 112.3, 99.8, 66.6, 63.7, 59.1, 57.5, 55.6, 21.0, 14.0; HR-MS (ESI) calcd for C32H26N4NaO6 [(M + Na)+]: 585.1750; Found: 585.1748. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-6a-(4-methoxyphenyl)-4-(4-nitrophenyl)-5-(p-tolyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3b). Bright yellow solid, 501 mg, yield: 89%; mp 197.1−197.6 °C (EA/PE); IR (KBr, cm−1): 3409, 3322, 3221, 3170, 2994, 2929, 2206, 1553, 1513, 1441, 1337, 1236, 1107, 1023, 851, 786; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.19 (s, 2H), 8.10 (d, J = 8.1 Hz, 2H), 7.55 (d, J = 8.1 Hz, 2H), 7.43 (d, J = 7.0 Hz, 1H), 7.07 (s, 3H), 7.05−6.95 (m, 3H), 6.90 (s, 1H), 5.49 (s, 1H), 3.98−3.95 (m, 2H), 3.77 (s, 3H), 2.20 (s, 3H), 1.08 (t, J = 6.6 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.3, 159.8, 145.5, 143.0, 141.6, 137.8, 135.4, 132.7, 130.5, 129.1, 128.8, 123.6, 123.5, 116.0, 115.8, 115.1, 112.3, 99.8, 66.6, 63.7, 59.1, 57.5, 55.7, 20.9, 14.1; HR-MS (ESI) calcd for C32H26N4NaO6 [(M + Na)+]: 585.1750; Found: 585.1745.

Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(4-bromophenyl)-3,6-dicyano-6a-(4-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3c). Bright yellow solid, 546 mg, yield: 87%; mp 222.3−223.3 °C (EA/PE); IR (KBr, cm−1): 3403, 3325, 3177, 2998, 2202, 1743, 1634, 1553, 1512, 1429, 1332, 1227, 1107, 1021; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.17 (s, 2H), 8.11 (d, J = 8.7 Hz, 2H), 7.55 (d, J = 8.6 Hz, 2H), 7.45 (d, J = 8.3 Hz, 2H), 7.32 (d, J = 8.7 Hz, 2H), 7.12 (d, J = 8.3 Hz, 2H), 7.05 (d, J = 8.7 Hz, 2H), 5.49 (s, 1H), 4.00 (q, J = 7.1 Hz, 2H), 3.78 (s, 3H), 1.10 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.2, 160.8, 145.5, 143.6, 141.3, 135.2, 133.1, 132.7, 131.7, 131.2, 129.3, 128.8, 127.8, 127.3, 125.4, 123.7, 123.5, 122.0, 115.8, 115.1, 114.8, 114.6, 100.0, 66.4, 63.8, 58.6, 57.6, 55.6, 14.1; HR-MS (ESI) calcd for C31H23BrN4NaO6 [(M + Na)+]: 649.0699; Found: 649.0706. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(4-chlorophenyl)-3,6-dicyano-6a-(3-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3d). Bright yellow solid, 513 mg, yield: 88%; mp 191.5−192.2 °C (EA/PE); IR (KBr, cm−1): 3364, 3178, 2930, 2838, 2202, 1742, 1634, 1558, 1502, 1446, 1377, 1249, 1106, 1025; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.22 (s, 2H), 8.11 (s, 2H), 7.60 (s, 2H), 7.44 (s, 1H), 7.31 (s, 2H), 7.22 (s, 2H), 7.11 (s, 1H), 7.02 (s, 1H), 6.91 (s, 1H), 5.60 (s, 1H), 4.01 (s, 2H), 3.78 (s, 3H), 1.09 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.1, 159.9, 145.6, 143.3, 141.2, 135.3, 134.8, 133.3, 132.8, 132.4, 131.0, 129.3, 128.8, 128.3, 123.7, 118.3, 115.7, 115.3, 114.9, 112.3, 99.8, 66.4, 63.8, 58.7, 57.6, 55.7, 14.1; HR-MS (ESI) calcd for C31H23ClN4NaO6 [(M + Na)+]: 605.1204; Found: 605.1205. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(4-chlorophenyl)-3,6-dicyano-6a-(4-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3e). Bright yellow solid, 513 mg, yield: 88%; mp 204.5−205.7 °C (EA/PE); IR (KBr, cm−1): 3385, 3168, 2933, 2835, 2201, 1742, 1635, 1549, 1443, 1369, 1248, 1106, 1029; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.18 (s, 2H), 8.12 (d, J = 7.8 Hz, 2H), 7.56 (d, J = 7.9 Hz, 2H), 7.33 (s, 4H), 7.20 (d, J = 7.3 Hz, 2H), 7.06 (d, J = 7.8 Hz, 2H), 5.52 (s, 1H), 4.01 (d, J = 6.6 Hz, 2H), 3.79 (s, 3H), 1.11 (d, J = 6.4 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.2, 160.8, 145.5, 143.6, 141.3, 134.8, 133.3, 132.6, 129.0, 128.6, 127.6, 125.4, 123.6, 115.9, 115.1, 114.9, 114.7, 100.0, 66.5, 63.8, 58.5, 57.6, 55.7, 14.0; HR-MS (ESI) calcd for C31H23ClN4NaO6 [(M + Na)+]: 605.1204; Found: 605.1219. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-6a-(4-methoxyphenyl)-4-(4-nitrophenyl)-5-(m-tolyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3f). Bright yellow solid, 501 mg, yield: 89%; mp 218.4−219.2 °C (EA/PE); IR (KBr, cm−1): 3402, 3328, 3176, 2995, 2212, 1753, 1643, 1508, 1429, 1335, 1234, 1101, 1022; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.12 (s, 2H), 8.09 (d, J = 8.6 Hz, 2H), 7.51 (d, J = 8.6 Hz, 2H), 7.31 (d, J = 8.5 Hz, 2H), 7.13−6.96 (m, 5H), 6.92 (d, J = 7.5 Hz, 1H), 5.40 (s, 1H), 4.07−3.87 (m, 2H), 3.78 (s, 3H), 2.16 (s, 3H), 1.10 (t, J = 7.0 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 180.1, 168.1, 165.5, 150.1, 148.1, 146.4, 142.24, 140.5, 136.2, 133., 133.7, 133.0, 132.6, 132.3, 130.3, 128.2, 120.7, 120.2, 119.9 119.4, 104.8, 71.4, 68.4, 63.9, 62.3, 60.5, 26.1, 18.8; HR-MS (ESI) calcd for C32H26N4NaO6 [(M + Na)+]: 585.1750; Found: 585.1761. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-6a-(3-chlorophenyl)-3,6dicyano-5-(4-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3g). Bright yellow solid, 519 mg, yield: 89%; mp 158.6−159.6 °C (EA/PE); IR (KBr, cm−1): 3394, 3179, 2945, 2208, 1548, 1356, 1248, 1108, 1021, 886, 789, 506; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.17 (s, 2H), 8.11 (s, 2H), 7.56 (s, 2H), 7.32 (s, 4H), 7.20 (s, 2H), 7.06 (s, 2H), 5.51 (s, 1H), 4.01 (s, 2H), 3.79 (s, 3H), 1.11 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.2, 160.8, 145.5, 143.6, 141.3, 134.8, 133.3, 132.6, 129.0, 128.6, 127.6, 125.4, 123.6, 115.9, 115.1, 114.9, 114.7, 100.0, 66.5, 63.8, 58.5, 57.6, 55.7, 14.0; HR-MS (ESI) calcd for C31H23ClN4NaO6 [(M + Na)+]: 605.1204; Found: 605.1201. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-5,6a-bis(4methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5H-cyclopenta[b]14772

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry furan-6-carboxylate (3h). Bright yellow solid, 503 mg, yield: 87%; mp 197.1−197.8 °C (EA/PE); IR (KBr, cm−1): 3426, 3306, 3221, 3170, 2925, 2211, 1744, 1635, 1549, 1432, 1330, 1239, 1106, 1029; 1 H NMR (400 MHz, DMSO-d6) δ (ppm): 9.14 (s, 2H), 8.09 (s, 2H), 7.53 (s, 2H), 7.30 (s, 2H), 7.07 (d, J = 9.0 Hz, 4H), 6.79 (s, 2H), 5.40 (s, 1H), 3.99 (s, 2H), 3.78 (s, 3H), 3.67 (s, 3H), 1.10 (s, 3H); 13 C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.4, 160.7, 159.2, 145.4, 143.1, 141.7, 131.9, 129.0, 127.5, 125.5, 123.5, 116.0, 115.7, 115.3, 114.7, 113.9, 99.9, 66.8, 63.6, 58.7, 57.5, 55.7, 55.3, 14.0; HR-MS (ESI) calcd for C32H26N4NaO7 [(M + Na)+]: 601.1699; Found: 601.1701. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-5-(3-methoxyphenyl)-4-(4-nitrophenyl)-6a-(m-tolyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3i). Bright yellow solid, 506 mg, yield: 90%; mp 183.5−184.3 °C (EA/PE); IR (KBr, cm−1): 3412, 3307, 3217, 3172, 2926, 2201, 1753, 1643, 1558, 1509, 1446, 1334, 1237, 1105, 1032; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.15 (s, 2H), 8.06 (d, J = 8.4 Hz, 2H), 7.51 (d, J = 8.3 Hz, 2H), 7.40 (dd, J = 7.9 Hz, 1H), 7.05 (d, J = 6.2 Hz, 2H), 7.03−6.93 (m, 3H), 6.90 (d, J = 7.2 Hz, 1H), 6.85 (s, 1H), 5.45 (s, 1H), 4.08−3.84 (m, 2H), 3.73 (s, 3H), 2.13 (s, 3H), 1.04 (t, J = 6.9 Hz, 3H); 13C{1H} NMR (150 MHz, DMSO-d6) δ (ppm): 174.9, 162.8, 159.4, 145.0, 142.6, 141.2, 137.0, 135.2, 135.0, 131.0, 130.2, 128.7, 128.4, 127.8, 127.3, 123.1, 117.8, 115.4, 114.7, 114.5, 111.8, 99.4, 66.1, 63.2, 58.8, 57.1, 26.3, 20.9, 13.5; HR-MS (ESI) calcd for C32H26N4NaO6 [(M + Na)+]: 585.1750; Found: 585.1747. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(4-bromophenyl)-3,6-dicyano-6a-(3-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3j). Bright yellow solid, 565 mg, yield: 90%; mp 163.1−164.0 °C (EA/PE); IR (KBr, cm−1): 3398, 3182, 2926, 2207, 1743, 1642, 1588, 1369, 1242, 1107, 1028; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.21 (s, 2H), 8.10 (s, 2H), 7.58 (s, 2H), 7.44 (s, 3H), 7.11 (s, 3H), 6.99 (s, 1H), 6.88 (s, 1H), 5.57 (s, 1H), 3.99 (s, 2H), 3.77 (s, 3H), 1.07 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.1, 159.8, 145.6, 143.3, 141.2, 135.2, 132.9, 131.5, 130.7, 129.0, 123.6, 122.0, 118.2, 115.7, 115.3, 114.9, 112.3, 99.8, 66.3, 63.9, 58.8, 57.5, 55.6, 14.0; HR-MS (ESI) calcd for C31H23BrN4NaO6 [(M + Na)+]: 649.0699; Found: 649.0693. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-5-(4-methoxyphenyl)-4-(4-nitrophenyl)-6a-(m-tolyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3k). Bright yellow solid, 512 mg, yield: 91%; mp 197.0−197.8 °C(EA/PE); IR (KBr, cm−1): 3410, 3318, 3170, 2996, 2935, 2208, 1554, 1512, 1441, 1336, 1236, 1107, 1023, 971, 893, 749, 462; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.18 (s, 2H), 8.09 (d, J = 7.1 Hz, 2H), 7.54 (d, J = 7.1 Hz, 2H), 7.42 (s, 1H), 7.25−6.89 (m, 6H), 6.88 (s, 1H), 5.48 (s, 1H), 3.97 (s, 2H), 3.76 (s, 3H), 2.18 (s, 3H), 1.06 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.3, 163.3, 159.8, 145.5, 142.9, 141.6, 137.8, 135.4, 132.7, 130.7, 130.6, 129.1, 129.0, 123.6, 118.2, 116.0, 115.8, 115.2, 115.0, 112.3, 99.8, 66.6, 63.7, 59.1, 57.4, 55.6, 21.0, 14.0; HRMS (ESI) calcd for C32H26N4NaO6 [(M + Na)+]: 585.1750; Found: 585.1753. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-5-(2,3dihydrobenzo[b][1,4]dioxin-6-yl)-6a-(3-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5H-cyclopenta[b]furan-6-carboxylate (3l). Bright yellow solid, 534 mg, yield: 88%; mp 159.1−159.8 °C (EA/ PE); IR (KBr, cm−1): 3356, 3179, 2934, 2205, 1747, 1647, 1566, 1509, 1444, 1387, 1338, 1290, 1242, 1113, 1057, 1031; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.17 (s, 2H), 8.12 (d, J = 8.7 Hz, 2H), 7.55 (d, J = 8.5 Hz, 2H), 7.42 (dd, J = 8.1 Hz, 1H), 7.08 (d, J = 8.8 Hz, 1H), 6.95 (d, J = 7.7 Hz, 1H), 6.85 (s, 1H), 6.68 (d, J = 8.5 Hz, 2H), 6.59 (d, J = 8.6 Hz, 1H), 5.40 (s, 1H), 4.15 (s, 4H), 3.98 (q, J = 5.2 Hz, 2H), 3.76 (s, 3H), 1.07 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.3, 163.3, 159.8, 145.5, 143.5, 143.0, 142.8, 141.6, 135.4, 130.7, 128.9, 128.5, 123.7, 123.6, 119.3, 118.2, 117.0, 115.9, 115.8, 115.2, 115.1, 112.3, 99.7, 66.5, 64.3, 63.7, 58.7, 57.4, 55.6, 55.3, 14.0; HR-MS (ESI) calcd for C33H26N4NaO8 [(M + Na)+]: 629.1648; Found: 629.1645. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-6a-(3-methoxyphenyl)-4-(4- nitrophenyl)-5-(thiophen-2-yl)-6,6a-dihydro-

5H-cyclopenta[b]furan-6-carboxylate (3m). Bright yellow solid, 494 mg, yield: 89%; mp 127.6−128.2 °C (EA/PE); IR (KBr, cm−1): 3451, 3339, 3160, 2942, 2838, 2205, 1731, 1636, 1594, 1560, 1518, 1340, 1254, 1110, 1026; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.21 (s, 2H), 8.13 (s, 2H), 7.60 (s, 2H), 7.41 (s, 2H), 7.09 (s, 1H), 6.97 (s, 1H), 6.87 (s, 2H), 6.79 (s, 1H), 5.80 (s, 1H), 4.00 (s, 2H), 3.76 (s, 3H), 1.08 (s, 3H); 13C{1H} NMR (100 MHz, DMSOd6) δ (ppm): 175.2, 163.1, 159.9, 145.7, 142.7, 141.5, 138.0, 135.0, 130.8, 129.6, 129.0, 127.4, 127.2, 123.5, 118.2, 115.7, 115.6, 115.3, 115.0, 112.2, 99.3, 67.1, 63.9, 57.2, 55.6, 55.0, 14.0; HR-MS (ESI) calcd for C29H22N4NaO6S [(M + Na)+]: 577.1158; Found: 577.1152. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(3-chlorophenyl)-3,6-dicyano-6a-(4-methoxyphenyl)-4-(4-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3n). Bright yellow solid, 490 mg, yield: 84%; mp 184.6−185.8 °C (EA/PE); IR (KBr, cm−1): 3429, 3326, 3179, 2985, 2204, 1753, 1634, 1558, 1508, 1323, 1231, 1100, 1019; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.17 (s, 2H), 8.11 (d, J = 7.1 Hz, 2H), 7.56 (d, J = 7.0 Hz, 2H), 7.42−7.15 (m, 5H), 7.10 (s, 1H), 7.05 (s, 2H), 5.52 (s, 1H), 3.99 (s, 2H), 3.78 (s, 3H), 1.10 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.4, 163.2, 160.8, 145.5, 143.8, 141.3, 138.2, 132.9, 130.8, 130.3, 129.5, 129.0, 128.6, 127.5, 125.3, 123.6, 115.8, 115.0, 114.7, 99.9, 66.4, 63.9, 58.6, 57.5, 55.7, 14.0; HR-MS (ESI) calcd for C31H23ClN4NaO6 [(M + Na)+]: 605.1204; Found: 605.1212. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-6a-(4-bromophenyl)-3,6dicyano-4-(4-nitrophenyl)-5-(p-tolyl)-6,6a-dihydro-5H-cyclopenta[b]furan-6-carboxylate (3o). Bright yellow solid, 526 mg, yield: 86%; mp 195.1−195.9 °C (EA/PE); IR (KBr, cm−1): 3384, 3222, 3153, 2926, 2837, 2200, 1743, 1636, 1526, 1450, 1343, 1287, 1162, 1106; 1 H NMR (400 MHz, DMSO-d6) δ (ppm): 9.20 (s, 2H), 8.10 (d, J = 8.2 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H), 7.52 (d, J = 8.4 Hz, 2H), 7.33 (d, J = 8.0 Hz, 2H), 7.05−7.02 (m, 4H), 5.44 (s, 1H), 3.99 (q, J = 6.8, 2H), 2.19 (s, 3H), 1.08 (t, J = 7.0 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.1, 163.2, 145.5, 142.4, 141.4, 137.8, 133.3, 132.5, 130.6, 129.2, 128.3, 123.9, 123.5, 116.3, 115.7, 114.9, 99.5, 66.6, 63.9, 59.0, 57.3, 21.0, 14.0; HR-MS (ESI) calcd for C31H23BrN4NaO5 [(M + Na)+]: 633.0750; Found: 633.0749. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-3,6-dicyano-6a-(3-methoxyphenyl)-4-(4-nitrophenyl)-5-(m-tolyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3p). Bright yellow solid, 501 mg, yield: 89%; mp 170.3−171.4 °C (EA/PE); IR (KBr, cm−1): 3408, 3309, 3171, 2995, 2202, 1742, 1633, 1552, 1510, 1444, 1336, 1234, 1107, 1020; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.18 (s, 2H), 8.09 (d, J = 8.4 Hz, 2H), 7.54 (d, J = 8.5 Hz, 2H), 7.43 (dd, J = 8.0 Hz, 1H), 7.09 (dd, J = 8.3, 4.8 Hz, 2H), 7.06−7.00 (m, 2H), 6.98 (d, J = 7.8 Hz, 1H), 6.93 (d, J = 7.5 Hz, 1H), 6.88 (s, 1H), 5.47 (s, 1H), 4.05−3.90 (m, 2H), 3.77 (s, 3H), 2.16 (s, 3H), 1.07 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 175.3, 163.3, 159.8, 145.5, 143.0, 141.6, 137.5, 135.7, 135.4, 131.4, 130.7, 129.1, 128.9, 128.3, 127.8, 123.5, 118.2, 115.9, 115.8, 115.2, 115.0, 112.3, 99.9, 66.6, 63.7, 59.3, 57.5, 55.6, 26.7, 14.0; HR-MS (ESI) calcd for C32H26N4NaO6 [(M + Na)+]: 585.1750; Found: 585.1737. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(4-bromophenyl)-3,6-dicyano-6a-(4-methoxyphenyl)-4-(2-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3q). Bright yellow solid, 533 mg, yield: 85%; mp 172.6−173.3 °C (EA/PE); IR (KBr, cm−1): 3358, 3230, 3184, 2919, 2846, 2208, 1732, 1652, 1517, 1452, 1346, 1298, 1171, 1102, 1017; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.09 (s, 2H), 7.87 (s, 1H), 7.80 (s, 2H), 7.51 (s, 3H), 7.35 (s, 2H), 7.11 (s, 2H), 6.89 (s, 2H), 5.07 (s, 1H), 3.98 (s, 2H), 3.82 (s, 3H), 1.08 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 174.6, 163.1, 160.9, 147.1, 134.1, 132.9, 131.4, 129.4, 129.0, 127.7, 125.5, 124.7, 122.3, 115.3, 114.7, 114.3, 99.7, 67.9, 63.8, 55.7, 55.3, 14.0; HR-MS (ESI) calcd for C31H23BrN4NaO6 [(M + Na)+]: 649.0699; Found: 649.0697. Ethyl (5R,6R,6aS/5S,6S,6aR)-2-Amino-5-(4-chlorophenyl)-3,6-dicyano-6a-(4-methoxyphenyl)-4-(2-nitrophenyl)-6,6a-dihydro-5Hcyclopenta[b]furan-6-carboxylate (3r). Bright yellow solid, 484 mg, yield: 83%; mp 187.6−188.2 °C (EA/PE); IR (KBr, cm−1): 3376, 3236, 3165, 2935, 2846, 2203, 1731, 1654, 1528, 1458, 1341, 1286, 1169, 1102; 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.09 (s, 2H), 14773

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry

furan-derived donor−acceptor cyclopropanes. Org. Biomol. Chem. 2013, 11, 3494−3509. (d) Garve, L. K. B.; Barkawitz, P.; Jones, P. G.; Werz, D. B. Ring-opening 1,3-dichlorination of donor−acceptor cyclopropanes by iodobenzene dichloride. Org. Lett. 2014, 16, 5804− 5807. (e) Racine, S.; de Nanteuil, F.; Serrano, E.; Waser, L. Synthesis of (carbo)nucleoside analogues by [3 + 2] annulation of aminocyclopropanes. Angew. Chem., Int. Ed. 2014, 53, 8484−8487. (f) Gupta, A.; Kholiya, R.; Rawat, D. S. BF3·OEt2-mediated highly stereoselective synthesis of trisubstituted-tetrahydrofuran via [3 + 2] cycloaddition reaction of 2-arylcyclopropyl ketones with aldehydes. Asian J. Org. Chem. 2017, 6, 993−997. (g) Sasazawa, K.; Takada, S.; Yubune, T.; Takaki, N.; Ota, R.; Nishii, Y. Stereochemical courses and mechanisms of ring-opening cyclization of donor−acceptor cyclopropylcarbinols and cyclization of 7-benzyloxy dibenzyl lignan lactones. Chem. Lett. 2017, 46, 524−526. (3) For reviews, see: (a) Melnikov, M. Y.; Budynina, E. M.; Ivanova, O. A.; Trushkov, I. V. Recent advances in ring-forming reactions of donor−acceptor cyclopropanes. Mendeleev Commun. 2011, 21, 293− 301. (b) Wang, Z. W. Polar intramolecular cross-cycloadditions of cyclopropanes toward natural product synthesis. Synlett 2012, 23, 2311−2327. (c) Tang, P.; Qin, Y. Recent applications of cyclopropane-based strategies to natural product synthesis. Synthesis 2012, 44, 2969−2984. (d) Mack, D.; Njardarson, J. Recent advances in the metal-catalyzed ring expansions of three- and four-membered rings. ACS Catal. 2013, 3, 272−286. (e) Cavitt, M. A.; Phun, L. H.; France, S. Intramolecular donor−acceptor cyclopropane ring-opening cyclizations. Chem. Soc. Rev. 2014, 43, 804−818. (f) Grover, H. K.; Emmett, M. R.; Kerr, M. A. Carbocycles from donor−acceptor cyclopropanes. Org. Biomol. Chem. 2015, 13, 655−671. (g) Gharpure, S. J.; Nanda, L. N. Application of oxygen/nitrogen substituted donor-acceptor cyclopropanes in the total synthesis of natural products. Tetrahedron Lett. 2017, 58, 711−720 and references cited therein. . (4) Liu, J. M.; Liu, X. Y.; Qing, X. S.; Wang, T.; Wang, C. D. I2/ K2CO3-promoted ring-opening/cyclization/rearrangement/ aromatization sequence: A powerful strategy for the synthesis of polysubstituted furans. Chin. Chem. Lett. 2017, 28, 458−462. (5) (a) Liu, J.; Zhou, L.; Ye, W.; Wang, C. Formal [3 + 2] cycloaddition of 1-cyanocyclopropane 1-ester with pyridine, quinoline or isoquinoline: a general and efficient strategy for construction of cyano -indolizine skeletons. Chem. Commun. 2014, 50, 9068−9071. (b) Tan, C.; Ye, W.; Yao, J.; Liu, J.; Xue, S.; Li, Y.; Wang, C. Efficient strategy for construction of 6-carbamoylfulvene-6-carboxylate skeletons via[3 + 2] cycloaddition of 1-cyanocyclopropane-1-ester with βnitrostyrenes. RSC Adv. 2015, 5, 26491−26495. (c) Ye, W.; Zhou, L.; Xue, S.; Li, Y.; Wang, C. Bimolecular intermolecular-Michael/ intramolecular-Michael/aromatization reaction of 1-cyanocyclopropane 1-esters or 1,1-dicyanocyclopropanes: A straightforward approach to fully substituted benzenes. Synlett 2015, 26, 1769− 1773. (d) Ye, W.; Tan, C.; Yao, J.; Xue, S.; Li, Y.; Wang, C. Iodinepromoted domino reactions of 1-cyanocyclopropane 1-esters: A straightforward approach to fully substituted 2-aminofurans. Adv. Synth. Catal. 2016, 358, 426−434. (e) Xue, S.; Liu, J.; Wang, C. DBUmediated [3 + 2] cycloaddition reactions of donor−acceptor cyclopropanes with nitromethane: Efficient strategy for the construction of isoxazole skeletons. Eur. J. Org. Chem. 2016, 2016, 2450− 2456. (f) Liu, J.; Ye, W.; Qing, X.; Wang, C. Solvent-Free DABCOmediated [3 + 2] cycloadditions of donor−acceptor cyclopropanes with aldehydes: strategy for synthesis of fully substituted furans. J. Org. Chem. 2016, 81, 7970−7976. (g) Su, Z.; Qian, S.; Xue, S.; Wang, C. DBU-mediated [4 + 1] annulations of donor− acceptor cyclopropanes with carbon disulfide or thiourea for synthesis of 2aminothiophene3-carboxylates. Org. Biomol. Chem. 2017, 15, 7878− 7886. (6) (a) Cao, W.; Zhang, H.; Chen, J.; Deng, H.; Shao, M.; Lei, L.; Qian, J.; Zhu, Y. A facile preparation of trans-1,2-cyclopropanes containing ptrifluoromethylphenylgroup and its application to the construction of pyrazole and cyclopropane ring fused pyridazinone derivatives. Tetrahedron 2008, 64, 6670−6674. (b) Han, Y.; Tang, W.Q.; Guo, L.-Y.; Yan, C.-G. Convenient synthesis of 1α,1β,2,5-

7.81 (s, 3H), 7.52 (s, 3H), 7.23 (s, 2H), 7.12 (s, 2H), 6.97 (s, 2H), 5.10 (s, 1H), 3.99 (s, 2H), 3.83 (s, 3H), 1.09 (s, 3H); 13C{1H} NMR (100 MHz, DMSO-d6) δ (ppm): 174.6, 163.1, 160.9, 147.1, 143.8, 134.20, 133.6, 132.9, 132.7, 129.4, 129.0, 128.5, 127.7, 125.4, 124.7, 115.3, 114.7, 114.4, 99.7, 67.8, 63.8, 58.4, 55.7, 14.0; HR-MS (ESI) calcd for C31H23ClN4NaO6 [(M + Na)+]: 605.1204; Found: 605.1206.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.8b02325. X-ray structure of 3h (CIF) X-ray structure of 3p (CIF) 1 H NMR and 13C NMR spectra of all the products (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*Fax: +86-514-8797-5244. Tel: +86-514-8797-5568. E-mail: [email protected]. ORCID

Cunde Wang: 0000-0001-5561-979X Author Contributions §

These authors contributed equally to this work.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS Financial support of this research by the National Natural Science Foundation of China (NNSFC 21173181) is gratefully acknowledged by the authors. A project was funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions (PPZY2015B112).

■

REFERENCES

(1) For reviews, see: (a) Reissig, H. U.; Zimmer, R. Donor− acceptor-substituted cyclopropane derivatives and their application in organic synthesis. Chem. Rev. 2003, 103, 1151−1196. (b) Yu, M.; Pagenkopf, B. L. Recent advances in donor−acceptor (DA) cyclopropanes. Tetrahedron 2005, 61, 321−347. (c) Carson, C. A.; Kerr, M. A. Heterocycles from cyclopropanes: applications in natural product synthesis. Chem. Soc. Rev. 2009, 38, 3051−3060. (d) Schneider, T.; Kaschel, J.; Werz, D. A new golden age for donor−acceptor cyclopropanes. Angew. Chem., Int. Ed. 2014, 53, 5504−5523. (e) O’Connor, N. R.; Wood, J. L.; Stoltz, B. M. Synthetic applications and methodological developments of donor−acceptor cyclopropanes and related compounds. Isr. J. Chem. 2016, 56, 431− 444. (f) Wang, L.; Tang, Y. Asymmetric ring-opening reactions of donor-acceptor cyclopropanes and cyclobutanes. Isr. J. Chem. 2016, 56, 463−475 and references cited therein. . (2) For selected examples on cycloadditions of D−A cyclopropane, see: (a) Kaschel, J.; Schneider, T. F.; Kratzert, D.; Stalke, D.; Werz, D. B. Domino reactions of donor−acceptor-substituted cyclopropanes for the synthesis of 3,3′-linked oligopyrroles and pyrrolo[3,2e]indoles. Angew. Chem., Int. Ed. 2012, 51, 11153−11156. (b) Kaschel, J.; Schmidt, C. D.; Mumby, M.; Kratzert, D.; Werz, D.; Stalke, D. B. Donor−acceptor cyclopropanes with Lawesson’s and Woollins’ reagents: formation of bisthiophenes and unprecedented cage-like molecules. Chem. Commun. 2013, 49, 4403−4405. (c) Kaschel, J.; Schneider, T. F.; Kratzert, K.; Stalke, D.; Werz, D. B. Symmetric and unsymmetric 3,3′-linked bispyrroles via ring-enlargement reactions of 14774

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry tetrahydro-1H-5a-aza-cyclopropa[a]indenes by base promoted cyclodimerization of 1,1-dicyano-2-aryl-3-benzoylcyclopropanes. Tetrahedron 2014, 70, 6663−6668. (c) Zhou, D.; Yu, H.; Liu, Y.; Chen, J.; Deng, H.; Shao, M.; Ren, Z.; Cao, W. A new stereoselective approach for the synthesis of substituted 3-cyclopropylmethylene-1,3-dihydroindol-2-one via the condensation reaction of cis-1-aryl-2-benzoyl-3,3dicyanocyclopropanes with oxindole in water. Tetrahedron Lett. 2010, 51, 5473−5475 and references cited therein . (7) Liu, J.; Qian, S.; Su, Z.; Wang, C. DBU-mediated [4 + 2] annulations of donor−acceptor cyclopropanes with 3-aryl-2-cyanoacrylates for the synthesis of fully substitutedanilines. RSC Adv. 2017, 7, 38342−38349. (8) (a) King, M. L.; Chiang, C.-C.; Ling, H.-C.; Fujita, E.; Ochiai, M.; McPhail, A. T. X-Ray crystal structure of rocaglamide, a novel antileulemic 1H-cyclopenta[b]benzofuran from Aglaia elliptifolia. J. Chem. Soc., Chem. Commun. 1982, 1150−1151. (b) Trost, B. M.; Greenspan, P. D.; Yang, B. V.; Saulnier, M. G. An unusual oxidative cyclization. A synthesis and absolute stereochemical assignment of (−)-rocaglamide. J. Am. Chem. Soc. 1990, 112, 9022−9024. (c) Malona, J. A.; Cariou, K.; Spencer, W. T., III; Frontier, A. J. Total synthesis of (±)-rocaglamide via oxidation-initiated Nazarov cyclization. J. Org. Chem. 2012, 77, 1891−1908. (9) Kobayashi, J. i.; Watanabe, D.; Kawasaki, N.; Tsuda, M. Nakadomarin A, a novel hexacyclic manzamine-related alkaloid from Amphimedon Sponge. J. Org. Chem. 1997, 62, 9236−9239. (10) Takeya, K.; Hitotsuyanagi, Y.; Hikita, M.; Nakada, K.; Fukaya, H. Sessilifoliamide I, a new alkaloid from Stemona sessilifolia. Heterocycles 2007, 71, 2035−2040. (11) Yang, B. O.; Ke, C.-Q.; He, Z.-S.; Yang, Y.-P.; Ye, Y. Brazilide A, a novel lactone with an unprecedented skeleton from Caesalpinia sappan. Tetrahedron Lett. 2002, 43, 1731−1733. (12) (a) Ohno, K.; Nagase, H.; Matsumoto, K.; Nishiyama, H.; Nishio, S. In Advances in Prottaglandin, Thromboxane, and Leukotriene Research; Hayashi, O., Yamamoto, S., Eds.; Ravan Press: New York, 1985; Vol. 15. (b) Jhoti, H.; Cleasby, A.; Reid, S.; Thomas, J. P.; Weir, M.; Wonacott, A. Crystal structures of Thrombin complexed to a novel series of synthetic inhibitors containing a 5,5-trans-lactone template. Biochemistry 1999, 38, 7969−7977. (13) (a) Weir, M. P.; Bethell, S. S.; Cleasby, A.; Campbell, C. J.; Dennis, R. J.; Dix, C. J.; Finch, H.; Jhoti, H.; Mooney, C. J.; Patel, S.; Tang, C.-M.; Ward, M.; Wonacott, A. J.; Wharton, C. W. Novel natural product 5,5-trans-lactone inhibitors of human α-Thrombin: mechanism of action and structural studies. Biochemistry 1998, 37, 6645−6657. (b) Kelly, H. A.; Bolton, R.; Brown, S. A.; Coote, S. J.; Dowle, M.; Dyer, U.; Finch, H.; Golding, D.; Lowdon, A.; McLaren, J.; Montana, J. G.; Owen, M. R.; Pegg, N. A.; Ross, B. C.; Thomas, R.; Walker, D. A. Synthesis of trans-fused [5,5] bicyclic lactones/lactams as templates for serine protease inhibition. Tetrahedron Lett. 1998, 39, 6979−6982. (c) Finch, H.; Pegg, N. A.; McLaren, J.; Lowdon, A.; Bolton, R.; Coote, S. J.; Dyer, U.; Montana, J. G.; Owen, M. R.; Dowle, M.; Buckley, D.; Ross, B. C.; Campbell, C.; Dix, C. J.; Mooney, C. J.; Tang, C. M.; Patel, C. 5,5-Trans lactone-containing inhibitors of serine proteases: Identification of a novel, acylating thrombin inhibitor. Bioorg. Med. Chem. Lett. 1998, 8, 2955−2960. (d) Pass, M.; Bolton, R. E.; Coote, S. J.; Finch, H.; Hindley, S.; Lowdon, A.; McDonald, E.; McLaren, J.; Owen, M.; Pegg, N. A.; Mooney, C. J.; Tang, C.-M.; Parry, S.; Patel, C. Synthetic [5,5] transfused Indane lactones as inhibitors of thrombin. Bioorg. Med. Chem. Lett. 1999, 9, 431−436. (14) Ghosh, A. K.; Sridhar, P. R.; Leshchenko, S.; Hussain, A. K.; Li, J.; Kovalevsky, A. Y.; Walters, D. E.; Wedekind, J. E.; Grum-Tokars, V.; Das, D.; Koh, Y.; Maeda, K.; Gatanaga, H.; Weber, I. T.; Mitsuya, H. Structure-based design of novel HIV-1 protease inhibitors to combat drug resistance. J. Med. Chem. 2006, 49, 5252−5261. (15) (a) Gomez-Roldan, V.; Fermas, S.; Brewer, P. B.; Puech-Pags, V.; Dun, E. A.; Pillot, J. P.; Letisse, F.; Matusova, R.; Danoun, S.; Portais, J. C.; Bouwmeester, H.; Bcard, G.; Beveridge, C. A.; Rameau, C.; Rochange, S. F. Strigolactone inhibition of shoot branching. Nature 2008, 455, 189−194. (b) Humphrey, A. J.; Galster, A. M.;

Beale, M. H. Strigolactones in chemical ecology: waste products or vital allelochemicals? Nat. Prod. Rep. 2006, 23, 592−614. (c) Dun, E. A.; Brewer, P. B.; Beveridge, C. A. Strigolactones: discovery of the elusive shoot branching hormone. Trends Plant Sci. 2009, 14, 364− 372. (d) Umehara, M.; Hanada, A.; Yoshida, S.; Akiyama, K.; Arite, T.; Takeda-Kamiya, N.; Magome, H.; Kamiya, Y.; Shirasu, K.; Yoneyama, K.; Kyozuka, J.; Yamaguchi, S. Inhibition of shoot branching by new terpenoid plant hormones. Nature 2008, 455, 195− U29. (16) Lachia, M.; Jung, P. M. J.; De Mesmaeker, A. A novel approach toward the synthesis of strigolactones through intramolecular [2 + 2] cycloaddition of ketenes and ketene-iminiums to olefins. Application to the asymmetric synthesis of GR-24. Tetrahedron Lett. 2012, 53, 4514−4517. (17) Dutta, L.; Bhuyan, P. J. Synthesis of highly functionalized indeno[1,2-b]furans. Tetrahedron Lett. 2017, 58, 3545−3548. (18) Duan, Y. N.; Cui, L. Q.; Zuo, L. H.; Zhang, C. Recyclable hypervalent-iodine-mediated dehydrogenative alpha,β ’-bifunctionalization of β-keto esters under metal-free conditions. Chem. - Eur. J. 2015, 21, 13052−13057. (19) Malik, H.; Rutjes, F. P. J. T.; Zwanenburg, B. A new efficient synthesis of GR24 and dimethyl A-ring analogues, germinating agents for seeds of the parasitic weeds Striga and Orobanche spp. Tetrahedron 2010, 66, 7198−7203. (20) (a) Salmanpour, S.; Ramazani, A.; Ahmadi, Y. Synthesis of stabilized phosphorus ylides from electron-poor alcohols and their applications in the preparation of 2,5-dihydrofuran derivatives. Bull. Chem. Soc. Ethiop. 2012, 26, 153−158. (b) Mouriès, C.; Deguin, B.; Koch, M.; Tillequin, F. Stereoselective conversion of aucubin into polyfunctionalized tetrahydro-1H-cyclopenta[c]furan glucosides. Helv. Chim. Acta 2003, 86, 147−156. (21) Ashley, W. L.; Timpy, E. L.; Coombs, T. C. Flow photoNazarov reactions of 2-furyl vinyl ketones: cyclizing a class of traditionally unreactive heteroaromatic enones. J. Org. Chem. 2018, 83, 2516−2529. (22) Le Floch, C.; Laymand, K.; Le Gall, E.; Leonel, E. A. Cobaltcatalyzed domino route to the ABC tricyclic core of strigolactones and analogues. Adv. Synth. Catal. 2012, 354, 823−827. (23) (a) Chen, V. X.; Boyer, F. D.; Rameau, C.; Pillot, J. P.; Vorsand, J. P.; Beau, J. M. New synthesis of A-ring aromatic strigolactone analogues and their evaluation as plant hormones in Pea (Pisum sativum). Chem. - Eur. J. 2013, 19, 4849−4857. (b) Clive, D. L. J.; Cheng, H. Tandem ring-closing metathesis−radicalcyclization based on 4-(phenylseleno)butanal and methyl 3-(phenylseleno)propanoate - a route to bicyclic compounds. Chem. Commun. 2001, 605−606. (24) Chojnacka, K.; Santoro, S.; Awartani, R.; Richards, N. G. J.; Himo, F.; Aponick, A. Synthetic studies on the solanacol ABC ring system by cation-initiated cascade cyclization: implications for strigolactonebiosynthesis. Org. Biomol. Chem. 2011, 9, 5350−5353. (25) Vinoth, P.; Vivekanand, T.; Suryavanshi, P. A; Menéndez, J. C; Sasai, H.; Sridharan, V. Palladium(II)-catalyzed intramolecular carboxypalladation−olefin insertion cascade: direct access to indeno[1,2-b]furan-2-ones. Org. Biomol. Chem. 2015, 13, 5175−5181. (26) Ling, J.; Laugeois, M.; Michelet, V.; Ratovelomanana-Vidal, V.; Vitale, M. R. (3 + 2) Palladium(0)-catalyzed dearomatization of 2nitrobenzofurans through formal (3 + 2) cycloadditions with vinylcyclopropanes: A straightforward access to cyclopenta[b]benzofurans. Synlett 2018, 29, 928−932. (27) (a) Wu, J. S.; Zhang, X.; Zhang, Y. L.; Xie, J. W. Synthesis and antifungal activities of novel polyheterocyclic spirooxindole derivatives. Org. Biomol. Chem. 2015, 13, 4967−4975. (b) Gowrisankar, S.; Park, D. Y.; Kim, J. N. Synthesis of 2,3,4-trisubstituted 2,5dihydrofuran derivatives. Bull. Korean Chem. Soc. 2005, 26, 1826− 1828. (28) CCDC 1588435 (for 3h) and 1570783 (for 3p) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre. 14775

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776

Note

The Journal of Organic Chemistry (29) Wang, Q.; Song, X.; Chen, J.; Yan, C. Pyridinium ylide-assisted one-pot two-step tandem synthesis of polysubstituted cyclopropanes. J. Comb. Chem. 2009, 11, 1007−1010.

14776

DOI: 10.1021/acs.joc.8b02325 J. Org. Chem. 2018, 83, 14768−14776