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Synlett 2018; 29(09): 1223-1228
DOI: 10.1055/s-0036-1591956
DOI: 10.1055/s-0036-1591956
letter
Efficient Access to cis-Hydrobenzo[b]oxepines: Rhodium(I)-Catalyzed Cyclization of Cyclohexadienone-Tethered o-Tolyl-Substituted Alkynes
Financial support was generously provided by the 973 Program (2015CB856600), NSFC (21572251, 21572253, 21772063), and the Collaborative Innovation Center of Chemical Science and Engineering (Tianjin).
Further Information
Publication History
Received: 17 January 2018
Accepted after revision: 20 February 2018
Publication Date:
14 March 2018 (online)
Abstract
An efficient access to cis-hydrobenzo[b]oxepine frameworks has been established through rhodium(I)-catalyzed cyclization of cyclohexadienone-tethered o-tolyl-substituted alkynes (1,6-enynes). The cascade process involves regioselective α-arylrhodation of the alkyne, 1,4-rhodium migration, and conjugate addition to cyclohexadienone.
Supporting Information
- Supporting information for this article is available online at https://doi.org/10.1055/s-0036-1591956.
- Supporting Information
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References and Notes
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- 13 CCDC 1816856, 1816857, and 1816858 (3cj) contain the supplementary crystallographic data for compounds 3aa, 3cj, and 3cj, respectively. The data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
- 14 cis-Hydrobenz[b]oxepines 3; General Procedure To a dried Schlenk flask charged with substrate 1 (0.2 mmol), arylboronic acid 2 (0.6 mmol, 3.0 equiv), and [Rh(COD)OH]2 (2.3 mg, 2.5 mol%) under argon was added toluene (8 mL) followed by degassed H2O (10.8 μL, 3.0 equiv), and the resulting mixture was stirred at 70 °C overnight. The reaction was quenched with sat. aq NH4Cl (30 mL), and the mixture was extracted with EtOAc (2 × 30 mL). The organic phases were combined, washed with brine (50 mL), dried (Na2SO4), and concentrated under reduced pressure. The residue was purified by flash column chromatography (silica gel, hexane–EtOAc). (4aS*,7Z,11bS*)-4a-Methyl-7-(2-methylbenzylidene)-4a,6,7,11b-tetrahydrodibenzo[b,d]oxepin-2(1H)-one (3ca) Yellow oil; yield: 44.9 mg (68%). IR (KBr): 3059, 3018, 2973, 2925, 1682, 1599, 1487, 1371, 1266, 1237, 1168, 1131, 1116, 1099, 1029, 912, 890, 791, 738, 658 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.45 (dd, J = 7.4, 1.6 Hz, 1 H), 7.38 (td, J = 7.5, 1.4 Hz, 1 H), 7.34 (td, J = 7.4, 1.5 Hz, 1 H), 7.23–7.15 (m, 4 H), 7.00 (d, J = 7.4 Hz, 1 H), 6.71 (s, 1 H), 6.55 (d, J = 10.2 Hz, 1 H), 6.02 (d, J = 10.1 Hz, 1 H), 4.50 (s, 2 H), 3.46–3.33 (m, 1 H), 3.11 (dd, J = 17.7, 10.0 Hz, 1 H), 2.53 (dd, J = 17.7, 5.4 Hz, 1 H), 2.24 (s, 3 H), 1.37 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 199.0, 151.7, 142.1, 140.9, 137.0, 136.4, 135.5, 130.2, 129.3, 128.8, 128.4, 128.0, 128.0, 127.6, 125.9, 72.6, 62.7, 49.3, 40.0, 24.9, 20.0. ESI-MS: m/z = 353.1 [M + Na]+. HRMS (ESI): m/z [M + H]+ calcd for C23H23O2: 331.1693; found: 331.1690. (4aS*,7Z,11bS*)-4a-Ethyl-7-(2-methylbenzylidene)-4a,6,7,11b-tetrahydrodibenzo[b,d]oxepin-2(1H)-one (3fa) Light-yellow oil; yield: 48.8 mg (71%). IR (KBr): 2965, 2925, 2374, 2349, 2316, 1683, 1486, 1116, 1098, 765, 738, 672, 664 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.45 (dd, J = 7.4, 1.5 Hz, 1 H), 7.39–7.26 (m, 2 H), 7.24–7.16 (m, 4 H), 7.06 (d, J = 7.3 Hz, 1 H), 6.72 (s, 1 H), 6.67 (d, J = 10.3 Hz, 1 H), 6.15 (d, J = 10.3 Hz, 1 H), 4.48 (dd, J = 16.3, 1.8 Hz, 2 H), 3.52–3.38 (m, 1 H), 3.20 (dd, J = 17.7, 10.1 Hz, 1 H), 2.61 (dd, J = 17.7, 5.3 Hz, 1 H), 2.31 (s, 3 H), 1.94–1.71 (m, 2 H), 0.93 (t, J = 7.5 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ = 199.1, 150.3, 142.0, 141.0, 137.1, 136.4, 135.5, 130.1, 128.8, 128.4, 128.0, 127.9, 127.6, 125.9, 75.0, 62.5, 47.7, 40.0, 29.6, 20.0, 7.9. ESI-MS: m/z = 367.2 [M + Na]+. HRMS (ESI): m/z [M + Na]+ calcd for C24H24NaO2 367.1669; found: 367.1667. (4aS*,7Z,11bS*)-4a-Cyclohexyl-7-(2-methylbenzylidene)-4a,6,7,11b-tetrahydrodibenzo[b,d]oxepin-2(1H)-one (3ga) Light-yellow oil; yield: 51.1 mg (64%). IR (KBr): 3661, 3228, 2925, 2851, 2375, 2349, 2316, 2286, 1681, 1598, 1486, 1450, 1259, 1047, 814, 700, 672, 664 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.44 (dd, J = 7.5, 1.5 Hz, 1 H), 7.34 (td, J = 7.4, 1.4 Hz, 1 H), 7.30–7.25 (m, 2 H), 7.22–7.17 (m, 3 H), 7.11 (d, J = 6.7 Hz, 1 H), 6.89–6.80 (m, 2 H), 6.19 (d, J = 10.3 Hz, 1 H), 4.70–4.18 (m, 2 H), 3.64–3.51 (m, 1 H), 3.36 (dd, J = 17.1, 13.1 Hz, 1 H), 2.46 (dd, J = 17.1, 4.6 Hz, 1 H), 2.31 (s, 3 H), 1.86–1.60 (m, 7 H), 1.19–0.93 (m, 4 H). 13C NMR (100 MHz, CDCl3): δ = 199.8, 148.5, 137.5, 136.4, 135.4, 131.5, 130.2, 130.0, 128.9, 128.7, 128.0, 127.8, 127.6, 125.9, 75.9, 62.3, 47.4, 40.9, 29.7, 28.1, 26.5, 26.3, 26.0, 25.7, 20.0. ESI-MS: m/z = 421.1 [M + Na]+. HRMS (ESI): m/z [M + Na]+ calcd for C28H30NaO2: 421.2138; found: 421.2135. (4aS*,7Z,11bS*)-4a-Benzyl-7-(2-methylbenzylidene)-4a,6,7,11b-tetrahydrodibenzo[b,d]oxepin-2(1H)-one(3ha) Light-yellow oil; yield: 35.7 mg (44%). IR (KBr): 3066, 3023, 2850, 2922,2850, 2389, 2374, 2348, 2316, 1682, 1486, 1453, 1383, 1095, 911, 766, 737, 701, 673, 664 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.52 (dd, J = 7.4, 1.6 Hz, 1 H), 7.38 (td, J = 7.5, 1.5 Hz, 1 H), 7.33 (td, J = 7.4, 1.6 Hz, 1 H), 7.30–7.26 (m, 1 H), 7.25–7.11 (m, 9 H), 6.74 (s, 1 H), 6.55 (d, J = 10.3 Hz, 1 H), 6.13 (d, J = 10.3 Hz, 1 H), 4.76–4.50 (m, 2 H), 3.60–3.48 (m, 1 H), 3.27–3.08 (m, 2 H), 2.90 (d, J = 13.9 Hz, 1 H), 2.59 (dd, J = 17.7, 5.6 Hz, 1 H), 2.31 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 198.8, 149.5, 142.1, 140.7, 136.7, 136.4, 135.7, 135.5, 130.7, 130.2, 129.4, 129.0, 128.8, 128.3, 128.2, 128.1, 128.0, 127.6, 126.9, 125.9, 75.3, 63.2, 47.0, 43.7, 40.3, 20.0. ESI-MS: m/z = 429.1 [M + Na]+. HRMS (ESI): m/z [M + Na]+ calcd for C29H26NaO2: 429.1825; found: 429.1822. (4aS*,7Z,11bS*)-7-(2-Methylbenzylidene)-4a-phenyl-4a,6,7,11b-tetrahydrodibenzo[b,d]oxepin-2(1H)-one (3ia) Light-yellow oil; yield: 54.1 mg (69%). IR (KBr): 2931, 2383, 2376, 2357, 1924, 1865, 1730, 1716, 1683, 1670, 1561, 1456, 1267, 1160, 1065, 800, 700, 668, 656 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.48 (dd, J = 7.6, 1.4 Hz, 1 H), 7.36–7.26 (m, 6 H), 7.24–7.16 (m, 5 H), 6.86 (d, J = 7.5 Hz, 1 H), 6.78 (s, 1 H), 6.75 (d, J = 10.2 Hz, 1 H), 6.27 (d, J = 10.1 Hz, 1 H), 4.62–4.38 (m, 2 H), 4.00–3.89 (m, 1 H), 3.35 (dd, J = 17.6, 11.0 Hz, 1 H), 2.68 (dd, J = 17.6, 5.4 Hz, 1 H), 2.32 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 198.9, 150.3, 142.6, 142.0, 140.8, 136.4, 136.4, 135.5, 130.2, 130.0, 129.5, 129.0, 128.7, 128.4, 127.9, 127.8, 127.6, 126.5, 125.9, 76.5, 63.3, 48.9, 40.6, 20.0. ESI-MS: m/z = 415.1 [M + Na]+. HRMS (ESI): m/z [M + Na]+ calcd for C28H24NaO2: 415.1669; found: 415.1660.
For recent reviews on the desymmetrization of cyclohexadienones, see: