Synthesis and Thermal Reactivity of Pyrrolidine- and 2-Pyrrolidinone-Fused Cyclic Enediynes

Abstract

Various bicyclic enediynes containing pyrrolidine and pyrrolidinone moieties were synthesised. Thermal reactivity studies indicated the lowering of the onset temperature for Bergman cyclisation upon fusion of these heterocyclic systems onto the cyclic enediyne.

enediynes - pyrrolidines - pyrrolidinones - heterocyclic systems - Bergman cyclisation

References and Notes

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Spectroscopic Data: All new compounds were characterised by spectroscopic and analytical data. Compound 1: ¹H NMR: δ = 8.23 (2 H, dd, J _{o , m} = 6.9, 1.9 Hz), 8.00 (2 H, dd, J _{o , m} = 6.9, 1.9 Hz), 7.32-7.07 (4 H, m), 4.68, 4.19 (2 H, AB_q, J = 18.8 Hz), 3.78, 3.52 (2 H, AB_q, J = 16.6 Hz), 3.49-3.17 (5 H, m), 2.04-1.85 (4 H, m). ¹³C NMR: δ = 150.0, 143.5, 130.5, 129.8, 128.8, 128.7, 127.9, 126.9, 124.7, 123.9, 90.5, 87.2, 84.0, 82.4, 59.2, 56.0, 50.2, 45.1, 28.2, 23.9. MS (ES+): m/z = 436 [M + H⁺]. Compound 2: ¹H NMR: δ = 8.31 (2 H, dd, J _{o , m} = 7.0, 2.0 Hz), 7.98 (2 H, dd, J _{o , m} = 7.0, 2.0 Hz), 4.62 (2 H, dd, J = 18.6, 6.0 Hz), 4.33 (1 H, m), 4.21 (2 H, dd, J = 18.6,12 Hz), 3.79 (1 H, dd, J = 12.0, 3.4 Hz), 3.44 (1 H, t, J = 2.0 Hz), 2.65-2.37 (2 H, m), 2.27-2.15 (2 H, m). ¹³C NMR: δ = 174.7, 150.3, 143.4, 130.6, 130.2, 128.9, 128.7, 128.4, 125.9, 124.6, 124.4, 87.2, 86.5, 84.9, 83.7, 54.8, 48.0, 38.0, 32.6, 29.4, 22.1. MS (ES+): m/z = 450 [M+ H⁺], 263 [M⁺ - SO₂Ar]. Compound 3: δ = 6.43 (1 H, d, J = 10.8 Hz), 5.88-5.79 (2 H, m), 5.28 (1 H, d, J = 15.6 Hz), 4.51-4.42 (2 H, m), 4.12-4.04 (2 H, m), 3.69-3.41 (2 H, m), 2.25-2.14 (1 H, m), 1.97-1.88 (3 H, m). ¹³C NMR: δ = 121.7, 120.8, 94.7, 93.0, 86.6, 83.4, 67.1, 65.0, 55.5, 54.7, 49.0, 32.0, 30.6, 23.7. MS (ES+): m/z = 170 [M - OH]. Compound 4: ¹H NMR (200 MHz, CDCl₃): δ = 8.41 (2 H, dd, J = 8.8 Hz), 8.07 (2 H, dd, J = 8.8 Hz), 7.28 (H, m), 4.28 (2 H, s), 3.66 (2 H, s). ¹H NMR (200 MHz, DMSO-d ₆ ): δ = 8.39 (2 H, d), 8.13 (2 H, dd, J = 8.8 Hz), 7.32 (2 H, m), 4.40 (2 H, s), 3.53 (2 H, s). ¹³C NMR (50 MHz, CDCl₃): δ = 150.3, 142.5, 130.7, 128.7, 124.7, 124.6, 85.7, 84.7, 46.3, 40.0. ¹³C NMR (50 MHz, DMSO-d ₆ ): δ = 150.29, 142.4, 130.5, 129.2, 129.1, 124.9, 104.5, 86.7, 84.9, 45.7. MS (ES+): m/z = 598 [M⁺ + H₂O], 581 [M + H⁺], 394 [M⁺ - SO₂Ar].