Enantioselective Methoxyselenenylation of α,β-Unsaturated Aldehydes

Abstract

In this communication we propose a convenient methodology to effect the asymmetric methoxyselenenylation of β-aryl α,β-unsaturated aldehydes using as electrophilic reagent an optically pure sulfur-containing selenenyl chloride. Mechanistic aspects of the reaction were investigated and simple manipulations to prepare optically pure derivatives are reported.

Key words

selenium - asymmetric synthesis - aldehydes - electrophilic addition

References and Notes

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11

Physical and spectral data for selected new compounds are reported below: Compound 4a (C₂₁H₂₈O₃SSe): oil; [α]_D ^¹8.0
-40.9 (c = 1.38, CHCl₃). ^¹H NMR (400 MHz): δ = 7.35 (dd, 1 H, J = 1.4, 7.7 Hz), 7.15-7.25 (m, 6 H), 7.10 (dd, 1 H, J = 1.2, 7.5 Hz), 6.95 (dt, 1 H, J = 1.4, 7.5 Hz), 4.84 (d, 1 H, J = 2.9 Hz), 4.36 (d, 1 H, J = 9.1 Hz), 4.19 (q, 1 H, J = 6.9 Hz), 3.60 (dd, 1 H, J = 2.9, 9.1 Hz), 3.58 (s, 3 H), 3.56 (s, 3 H), 3.17 (s, 3 H), 1.87 (s, 3 H), 1.35 (d, 3 H, J = 6.9 Hz). ^¹³C NMR (100.62 MHz): δ = 145.9, 139.5, 136.1, 132.6, 128.6 (2 × CH_Ar), 128.2, 128.1 (2 × CH), 127.7, 127.3, 126.3, 105.7, 84.8, 57.7, 57.02, 57.01, 56.4, 43.7, 21.4, 13.9. GC-MS: m/z (%) = 442 (5), 440 (20) [M⁺], 438 (10), 436 (4), 231 (100), 215 (2), 183 (71), 121 (72), 91 (19), 75 (69). Compound 4b (C₂₁H₂₇O₃ClSSe): oil. ^¹H NMR (400 MHz):
δ = 7.35 (d, 1 H, J = 7.3 Hz), 7.15-7.20 (m, 2 H), 7.05-7.13 (m, 3 H), 6.95-7.00 (m, 2 H), 4.85 (d, 1 H, J = 2.6 Hz), 4.33 (d, 1 H, J = 9.4 Hz), 4.10 (q, 1 H, J = 6.9 Hz), 3.60 (s, 3 H), 3.59 (s, 3 H), 3.58 (dd, 1 H, J = 2.6, 9.4 Hz), 3.15 (s, 3 H), 1.90 (s, 3 H), 1.41 (d, 3 H, J = 6.9 Hz). ^¹³C NMR (100.62 MHz): δ = 145.2, 137.6, 135.6, 133.5, 132.0, 129.5 (2 × CH), 127.7 (2 × CH), 127.2, 126.9, 125.9, 105.2, 83.9, 57.4, 56.6, 56.4, 56.3, 43.2, 20.6, 13.2. GC-MS: m/z (%) = 476 (6), 474 (12) [M⁺], 472 (6), 470 (2), 231 (100), 215 (9), 183 (68), 155 (45), 135 (8), 91 (16), 75 (60). Compound 4c (C₂₂H₃₀O₃SSe): oil. ^¹H NMR (400 MHz): d = 7.38 (dd, 1 H, J = 1.3, 7.8 Hz), 7.19 (dd, 1 H, J = 1.7, 7.8 Hz), 7.14 (ddd, 1 H, J = 1.3, 7.3, 7.8 Hz) 7.04-7.08 (m, 2 H), 6.94-6.98 (m, 3 H), 4.83 (d, 1 H, J = 2.9 Hz), 4.32 (d, 1 H, J = 9.2 Hz), 4.15 (q, 1 H, J = 6.9 Hz), 3.58 (s, 3 H), 3.57 (dd, 1 H, J = 2.9, 9.2 Hz), 3.56 (s, 3 H), 3.16 (s, 3 H), 2.28 (s, 3 H), 1.87 (s, 3 H), 1.34 (d, 3 H, J = 6.9 Hz). ^¹³C NMR (100.62 MHz): δ = 145.4, 137.3, 136.0, 135.8, 132.3, 128.4 (2 × CH), 128.0 (2 × CH), 127.1, 126.8, 125.8, 105.3, 84.2, 57.4, 56.9, 56.5, 56.1, 43.3, 21.1, 20.9, 13.4. GC-MS: m/z (%) = 454 (21) [M⁺], 452 (10), 231 (72), 229 (37), 215 (11), 183 (49), 135 (100), 105(6), 91 (14), 75 (52). Compound 4e (C₂₅H₃₀O₃SSe): oil. ^¹H NMR (400 MHz): δ = 7.70-7.75 (m, 2 H), 7.69 (s, 1 H), 7.53 (d, 1 H, J = 8.5 Hz), 7.45-7.50 (m, 2 H), 7.33 (d, 1 H, J = 7.8 Hz), 7.19 (d, 1 H, J = 8.6 Hz), 7.00 (dd, 1 H, J = 7.6, 8.0 Hz), 6.92 (d, 1 H, J = 7.5 Hz), 6.80 (t, 1 H, J = 7.5 Hz), 4.93 (d, 1 H, J = 2.5 Hz), 4.52 (d, 1 H, J = 9.6 Hz), 3.83 (q, 1 H, J = 6.9 Hz), 3.71 (dd, 1 H, J = 2.5, 9.6 Hz), 3.63 (s, 3 H), 3.62 (s, 3 H), 3.25 (s, 3 H), 1.78 (s, 3 H), 0.88 (d, 3 H, J = 6.9 Hz). ^¹³C NMR (100.62 MHz): δ = 145.5, 136.9, 136.1, 133.6, 133.1, 132.7, 128.5, 128.4, 128.3, 127.9, 127.8, 127.4, 127.1, 126.3, 126.0, 125.7, 105.8, 85.2, 57.9, 57.0, 56.7, 43.6, 30.7, 20.3, 13.6. Compound 10 (C₂₀H₂₆O₂SSe): oil; [α]_D ^¹8.0 = 19.9 (c = 1.11, CHCl₃). ^¹H NMR (400 MHz): δ = 7.40 (d, 1 H, J = 8.0 Hz), 7.10-7.30 (m, 7 H), 7.00-7.05 (m, 1 H), 4.35 (d, 1 H, J = 9.5 Hz), 4.25-4.30 (m, 1 H), 4.03 (q, 1 H, J = 7.0 Hz), 3.72 (dd, 1 H, J = 4.5, 9.5 Hz), 3.18 (s, 3 H), 3.07 (d, 1 H, J = 9.1 Hz), 1.89 (s, 3 H), 1.41 (d, 3 H, J = 7.0 Hz), 1.38 (d, 3 H, J = 6.3 Hz). ^¹³C NMR (100.62 MHz): δ = 144.5, 139.3, 134.8, 132.0, 128.6, 127.91 (2 × CH), 127.88 (2 × CH), 127.4, 127.2, 125.9, 86.2, 67.4, 63.6, 56.9, 43.1, 21.1, 20.1, 13.0. GC-MS: m/z (%) = 410 (7) [M⁺], 408 (3), 231 (82), 229 (40), 215 (13), 194 (31), 183 (100), 181 (57), 147 (13), 121 (36), 105 (28), 91 (45), 77 (21), 51 (4).