Cyclopropane Formation via a Simple Barbier Reaction in DMF

Abstract

Cyclopropanes are prepared in good yields via magnes­ium activation of polyhalomethyl compounds (dichlorodiphenylmethane, methyl trichloroacetate, α,α,α-trichlorotoluene, benzal chloride, benzal bromide) in the presence of activated olefins in DMF.

Key words

cyclopropanation - activated olefins - α-halomagnesium reagents - Barbier reaction - carbenoids

References

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8

Spectral data for compound 4: Anal. Calcd: C, 86.36; H, 7.25. Found: C, 86.44; H, 7.31. Mp = 65-67 °C. ¹H NMR (200 MHz, CDCl₃): δ (ppm) = 7.20-7.10 (m, 10 H), 2.80 (dd, 1 H, J = 7.6, 5.7 Hz), 2.50 (q, 2 H, J = 7.3 Hz), 2.30 (dd, 1 H, J = 5.7, 4.6 Hz), 1.50 (dd, 1 H, J = 7.6, 4.6 Hz), 1.00 (t, 3 H, J = 7.3 Hz). ¹³C NMR (50.32 MHz, CDCl₃): δ (ppm) = 206.2, 145.2, 139.5, 129.9, 128.3, 127.6, 126.9, 126.5, 42.5, 37.5, 36.2, 20.8, 7.8. MS (EI): m/z (rel. intensity) = 250 (18), 235 (3), 221 (15), 193 (90), 192 (49), 191 (13), 178 (36), 165 (25), 116 (12), 115 (100), 91 (10), 77 (2). IR (KBr): ν = 3030, 2980, 1700, 1600, 1500, 1450 cm^-1.

9

Spectral data for compound 5: Anal. Calcd: C, 86.32; H, 7.63. Found: C, 85.91; H, 7.55. Mp = 111-112 °C. ¹H NMR (200 MHz, CDCl₃): δ (ppm) = 7.30-7.0 (m, 10 H), 2.50-2.35 (m, 4 H), 0.90 (t, 3 H, J = 7.3 Hz), 0.90 (d, 3 H, J = 5.7 Hz). ¹³C NMR (50.32 MHz, CDCl₃): δ (ppm) = 206.6, 141.5, 141.4, 129.3, 128.3, 128.1, 126.5, 48.5, 41.0, 37.3, 24.6, 14.6, 7.8. MS (EI): m/z (rel. intensity) = 264 (1), 235 (11), 207 (48), 206 (24), 191 (10), 179 (10), 178 (12), 165 (18), 130 (11), 129 (100), 128 (12), 91 (23), 77 (2). IR (KBr): ν = 3030, 3010, 2990, 1710, 1600, 1580 cm^-1.