Article pubs.acs.org/joc
N‑Heterocyclic Carbene Catalytic [4 + 2] Cyclization of 3‑Alkylenyloxindoles with Enals: γ‑Carbon Activation for Enantioselective Assembly of Spirocarbocyclic Oxindoles Hong Yao,†,‡,§ Yu Zhou,‡,§ Xia Chen,†,‡ Pengfei Zhang,†,‡ Jinyi Xu,*,† and Hong Liu*,†,‡ †
State Key Laboratory of Natural Medicines and Department of Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing, Jiangsu 210009, P. R. China ‡ Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, P. R. China S Supporting Information *
ABSTRACT: The ubiquitous structure of all-carbospirocyclic oxindoles makes the development of new methods for their enantioselective and stereoselective synthesis a significant ongoing challenge. Herein, we disclose a formal [4 + 2] annulation through N-heterocyclic carbene (NHC) catalysis for highly enantioselective synthesis of intriguing spirocarbocyclic oxindoles in the presence of Lewis acids. This protocol features good substrates tolerance, good yields, and excellent diastereoselectivities and enantioselectivities (up to 97% ee) under mild conditions.
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INTRODUCTION
the construction of a C3-quaternary stereocenters with a neighboring congested carbon stereocenter in a single assembly step under mild condition still remains a significant challenge. Over the past decade, the application of N-heterocyclic carbenes in chemistry has developed rapidly.3 Their unique umpolung nature has become an important strategy for synthesizing spiroheterocyclic oxindole compounds.4 After Nair’s pioneering synthesis of spirocyclic latones from 1,2diketones and enals,5 numerous spirocyclic lactones and lactams have been realized by Ye,6 Chi,7 Glorius,8 Scheidt,9 Wang,10 Yao,11 Lu,12 and Zhong13 et al. However, compared with these diversified NHC-catalyzed synthesis of spiroheterocycles, the all-carbon spirocarbocycles are still under developed. To the best of our knowledge, there are only a few reports concerning NHC-catalyzed synthesis of all-carbon spirocarbocyclic oxindoles. Chi et al.14 reported a pioneering NHCcatalyzed [3 + 2] annulation of oxindole-derived β,βdisubstituted imines and enals to produce spirocyclopenteneoxindoles with only 53% ee. Recently, Ye et al.15 (Scheme 1, eq 1) and Yao et al.16 (Scheme 1, eq 2) independently disclosed a facile [4 + 2] annulation of 3-alkylenyloxindoles with different highly active α,β-unsaturated aldehyde equivalents to give allcarbon spirocarbocyclic oxindoles; however, no high enantioselectivities were obtained (ee 99:1 dr, [α]D 20 = +130.6, (2.0 mg/mL, CHCl3), white solid. M.P.: 197.6−199.9 °C. 1H NMR (400 MHz, CDCl3): δ 7.50−7.44 (m, 2H), 7.41−7.36 (m, 2H), 7.35−7.29 (m, 1H), 7.08− 7.03 (m, 1H), 7.00−6.94 (m, 1H), 6.91 (d, J = 7.8 Hz, 1H), 6.16 (d, J = 1.6 Hz, 1H), 4.89 (s, 1H), 3.58−3.49 (m, 4H), 3.29 (s, 3H), 3.05− 2.97 (m, 2H). 13C NMR (126 MHz, CDCl3): δ 178.1, 170.6, 145.3, 136.8, 135.4, 133.6, 128.6, 128.4, 127.2, 126.2, 125.2, 124.1, 122.0, 107.9, 72.4, 53.3, 51.6, 43.9, 27.1, 26.2. HRMS (ESI-TOF): calculated for C22H20O4NClNa [M + Na]+, 420.0973; found, 420.0962. HPLC conditions: chiralpak IA-H, hexane/iso-PrOH = 75:25, flow rate = 1 mL/min, λ = 254 nm, and retention time = 8.449 min (major) and 12.557 min (minor). The dr was determined by LC−MS with an Eclipse-C18 column (250 × 4.6 mm, 5 μm) (MeOH/H2O = 60/40, flow rate 1.0 mL/min, λ = 254 nm) and tmajor = 13.886 min. (1R,6R)-1′-Methyl 4-Phenyl-6-(1-hydroxyethyl)-2′-oxospiro[cyclohex[3]ene-1,3′-indoline]-2-alcohol (8h). 9.9 mg, 51% yield, 89% ee, white solid, 89:11 dr, [α]D 20 = +159.3, (2.2 mg/mL, CHCl3). M.P.: 85.2−87.2 °C. 1H NMR (400 MHz, CDCl3): δ 7.60−7.54 (m, 2H), 7.45−7.38 (m, 2H), 7.38−7.31 (m, 2H), 7.21 (dd, J = 7.5, 0.6 Hz, 1H), 7.04−6.97 (m, 1H), 6.94 (d, J = 7.8 Hz, 1H), 6.16 (d, J = 1.6 Hz, 1H), 4.92 (s, 1H), 3.86−3.77 (m, 1H), 3.30 (s, 3H), 3.08−2.96 (m, 1H), 2.71 (dd, J = 18.4, 5.7 Hz, 1H), 2.58−2.48 (m, 1H), 1.11 (d, J = 6.5 Hz, 3H). 13C NMR (126 MHz, CDCl3): δ 178.4, 144.4, 139.2, 137.8, 128.7, 128.2, 127.6, 126.1, 125.9, 125.1, 124.9, 122.4, 108.3, 73.1, 67.5, 56.3, 44.9, 26.0, 22.9, 20.8. HRMS (ESI-TOF): calculated for C22H23O3NNa [M + Na]+, 372.1570; found, 372.1566. HPLC conditions: chiralpak IA-H, hexane/iso-PrOH = 75:25, flow rate = 1 mL/min, λ = 254 nm, and retention time = 7.343 min (major) and 9.305 min (minor). The dr was determined by LC−MS with an Eclipse-C18 column (250 × 4.6 mm, 5 μm) (MeOH/H2O = 60/40, flow rate 1.0 mL/min, λ = 254 nm), tmajor = 7.718 min, and tminor = 12.224 min.
127.0, 125.5, 123.0, 122.2, 108.7, 60.1, 52.2, 29.1, 28.3, 26.3. HRMS (ESI-TOF): calculated for C22H18O3NClNa [M + Na]+, 402.0867; found, 402.0859. HPLC conditions: chiralpak IA-H, hexane/iso-PrOH = 90:10, flow rate = 0.5 mL/min, λ = 254 nm, retention time = 64.632 min (major) and 75.134 min (minor). The dr was determined by LC− MS with an Extend-C18 column (150 × 4.6 mm, 5 μm) (MeOH/H2O = 65/35, flow rate 1.0 mL/min, λ = 254 nm), tmajor = 10.100 min, and tminor = 11.536 min, dr =96:4. (1R,6R)-Methyl 1′-Methyl 4-(4-Bromophenyl)-2,2′-dioxospiro[cyclohex[3]ene-1, 3′-indoline]-2,6-dione (5o). 29.7 mg, 47% yield, 78% ee, 94:6 dr, [α]D 20 = +265.8 (3.6 mg/mL, CHCl3), pale yellow solid. M.P.: 215.1−217.4 °C. 1H NMR (400 MHz, CDCl3): δ 7.65− 7.60 (m, 2H), 7.55−7.51 (m, 2H), 7.32−7.26 (m, 1H), 7.03 (d, J = 6.9 Hz, 1H), 6.97−6.94 (m, 1H), 6.91 (d, J = 7.8 Hz, 1H), 6.57 (d, J = 1.5 Hz, 1H), 4.06 (dd, J = 11.4, 5.6 Hz, 1H), 3.44−3.37 (m, 1H), 3.31 (s, 3H), 3.24 (dd, J = 18.9, 5.5 Hz, 1H), 2.11 (s, 3H). 13C NMR (126 MHz, CDCl3): δ 204.4, 192.1, 175.1, 155.8, 144.5, 136.2, 132.4, 129.3, 127.7, 125.9, 125.5, 124.1, 123.4, 122.6, 109.2, 60.5, 52.1, 29.0, 27.1, 26.8. HRMS (ESI-TOF): calculated for C22H18O3NBrNa [M + Na]+, 446.0362; found, 446.0364. HPLC conditions: chiralpak AD-H, hexane/iso-PrOH = 70:30, flow rate = 0.9 mL/min, λ = 254 nm, and retention time = 30.449 min (minor) and 45.697 min (major). The dr was determined by LC-MS with an Extend-C18 column (150 × 4.6 mm, 5 μm) (MeOH/H2O = 65/35, flow rate 1.0 mL/min, λ = 254 nm), tmajor = 14.286 min, and tminor = 18.041 min, dr =94:6. (1R,6R)-1′-Methyl-2′-hydroxy-4-phenyl-6-(hydroxymethyl)spiro[cyclohex[3]ene-1,3′-indoline]-2-one (6a). 13.1 mg, 78% yield, 92% ee, [α]D 20 = +144.2, (1.8 mg/mL, CHCl3), white solid. M.P.: 181.0− 183.2 °C. 1H NMR (400 MHz, CDCl3): δ 7.51−7.46 (m, 2H), 7.38 (dd, J = 8.1, 6.6 Hz, 2H), 7.35−7.29 (m, 1H), 7.24−7.18 (m, 1H), 7.05 (d, J = 7.8 Hz, 1H), 6.78−6.68 (m, 2H), 6.27 (s, 1H), 4.36 (d, J = 9.4 Hz, 1H), 3.74 (d, J = 4.4 Hz, 1H), 3.67 (d, J = 6.8 Hz, 1H), 3.54 (d, J = 8.8 Hz, 1H), 3.42 (dd, J = 12.2, 3.8 Hz, 1H), 3.15 (dd, J = 12.3, 8.8 Hz, 1H), 2.82 (s, 3H), 2.42−2.31 (m, 2H), 2.17−2.04 (m, 1H), 1.62 (br, 2H). 13C NMR (126 MHz, CDCl3): δ 191.2, 160.5, 139.8, 137.8, 129.2, 128.6, 127.9, 127.3, 126.9, 125.2, 124.9, 122.0, 109.6, 71.6, 65.4, 64.2, 52.4, 44.1, 28.0. HRMS (ESI-TOF): calculated for C21H21O3NNa [M + Na]+, 358.1414; found, 358.1409. HPLC conditions: chiralpak IA-H, hexane/iso-PrOH = 75:25, flow rate = 1 mL/min, λ = 254 nm, retention time = 8.484 min (major) and 15.269 min (minor). (1R,6R)-1′-Methyl-2′-hydroxy-4-(4-fluorophenyl)-6(hydroxymethyl)spiro[cyclo-hex[3]ene-1,3′-indoline]-2-one (6d). 13.3 mg, 75% yield, 84% ee, [α]D 20 = +161.2, (1.7 mg/mL, CHCl3), white solid. M.P.: 107.7−112.3 °C. 1H NMR (400 MHz, CDCl3): δ 7.53−7.46 (m, 1H), 7.35−7.28 (m, 1H), 7.08 (dd, J = 12.1, 5.3 Hz, 2H), 7.02−6.95 (m, 1H), 6.90 (d, J = 7.8 Hz, 1H), 6.14 (s, 1H), 4.91 (s, 1H), 3.31−3.18 (m, 3H), 2.85−2.67 (m, 1H), 2.52−2.41 (m, 1H), 1.69 (br, 2H). 13C NMR (126 MHz, CDCl3): δ 180.8, 164.1 (d, J = 247.6 Hz), 146.7, 138.0, 136.9, 130.4, 128.5, 128.4 (d, J = 8.1 Hz), 127.1, 126.5, 124.1, 116.9 (d, J = 21.4 Hz), 110.0, 74.4, 65.4, 56.9, 43.3, 29.7, 28.0. HRMS (ESI-TOF): calculated for C21H20O3NFNa [M + Na]+, 376.1319; found, 376.1318. HPLC conditions: chiralpak IA-H, hexane/iso-PrOH = 75:25, flow rate = 1 mL/min, λ = 254 nm, and retention time = 8.931 min (major) and 12.392 min (minor). (1R,6R)-1′-Methyl-2′-hydroxy-4-(4-chlorophenyl)-6(hydroxymethyl)spiro[cyclo-hex[3]ene-1,3′-indoline]-2-one (6e). 14.1 mg, 76% yield, 92% ee, [α]D20 = +147.1, (2.0 mg/mL, CHCl3), white solid. M.P.: 189.9−193.2 °C. 1H NMR (400 MHz, CDCl3): δ 7.47 (d, J = 8.6 Hz, 1H), 7.40−7.30 (m, 1H), 7.07 (d, J = 7.5 Hz, 1H), 6.99 (t, J = 7.6 Hz, 1H), 6.91 (d, J = 7.8 Hz, 1H), 6.19 (s, 1H), 4.93 (s, 1H), 3.32−3.21 (m, 1H), 2.84−2.66 (m, 1H), 2.49 (dd, J = 16.9, 10.3 Hz, 1H), 1.56 (br, 2H). 13C NMR (126 MHz, CDCl3): δ 179.15, 145.33, 137.76, 136.50, 133.95, 129.05, 128.80, 127.66, 126.63, 125.49, 124.99, 122.64, 108.55, 72.96, 63.97, 55.42, 41.87, 28.03, 26.57. HRMS (ESI-TOF): calculated for C21H20O3NClNa [M + Na]+, 392.1024; found, 392.1012. HPLC conditions: chiralpak IA-H, hexane/iso-PrOH = 75:25, flow rate = 1 mL/min, λ = 254 nm, and retention time = 9.849 min (major) and 13.695 min (minor). 8897
DOI: 10.1021/acs.joc.6b01596 J. Org. Chem. 2016, 81, 8888−8899
Article
The Journal of Organic Chemistry
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.6b01596. X-ray crystallography, 1H spectra, 13C NMR spectra, and HPLC chromatograms (PDF) (1R, 6R)-3f (CIF) (1R, 6R)-5g (CIF) (1R, 6R)-5i (CIF) (1R, 6R)-6h (CIF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. Author Contributions §
H.Y. and Y.Z. contributed equally.
Notes
The authors declare no competing financial interest. Crystallographic data (CCDC 1457039 (3f), 1457052 (5g), 1457058 (5i), and 1457169 (6h)) may be accessed free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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ACKNOWLEDGMENTS We gratefully acknowledge financial support from the National Natural Science Foundation of China (21632008, 21472209, 21672232 and 91229204), the Major Project of Chinese National Programs for Fundamental Research and Development (2015CB910304), the National Basic Research Program of China (2012CB518005), and National S&T Major Projects (2013ZX09507-001, and 2014ZX09507002-001), and China Pharmaceutical University (Grant SKLNMZZCX201404).
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DOI: 10.1021/acs.joc.6b01596 J. Org. Chem. 2016, 81, 8888−8899
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DOI: 10.1021/acs.joc.6b01596 J. Org. Chem. 2016, 81, 8888−8899
