Cyclopropanation of Olefins with Nitromethane

Abstract

A procedure for the use of nitromethane as an iodonium ylide precursor has been developed. Electron-rich olefins are cyclopropanated with nitromethane in the presence of bis(acetoxy)iodobenzene, a base and a Rh(II) catalyst to provide nitrocyclopropanes in moderate to good yields.

Key words

cyclopropanation - iodonium ylides - rhodium - nitro­cyclopropanes - nitrodiazomethane

References and Notes

• 1 Doyle MP. Ye T. McKervey MA. Modern Catalytic Methods for Organic Synthesis with Diazo Compounds: From Cyclopropanes to Ylides   Wiley; New York: 1998. 
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• 4 Charette AB. Wurz RP. Ollevier T. Helv. Chim. Acta  2002,  85:  4468 
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• 9 Georgakopoulou G. Kalogiros C. Hadjiarapoglou LP. Synlett  2001,  1843 
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14

General Experimental Procedure. PhI(OAc)₂ (203 mg, 0.616 mmol, 1.0 equiv) was added to a mixture of Rh₂(esp)₂ (23 mg, 0.031 mmol, 5 mol%), alkene (1.0 equiv), nitromethane (1.0 mL, 18.6 mmol, 30 equiv) and K₂CO₃ (187 mg, 1.36 mmol, 2.2 equiv). The reaction mixture was stirred at r.t. for 3 h. After 3 h reaction time, another portion of PhI(OAc)₂ (203 mg, 0.616 mmol, 1.0 equiv), K₂CO₃ (187 mg, 1.36 mmol, 2.2 equiv), Rh₂(esp)₂ (23 mg, 0.031 mmol, 5 mol%) and nitromethane (1.0 mL) was added and stirring was continued for another 3 h. The crude reaction mixture was diluted with CH₂Cl₂, washed with brine (3 × 5 mL), dried with MgSO₄, filtered and the solution concentrated in vacuo. Flash chromatography (0-10% EtOAc-hexane) yielded cyclopropanes 2a and 2b. All cyclopropanes 2-10a,b were characterized by ¹H NMR and ¹³C NMR, MS, HRMS and, when solid, mp.
Spectroscopic Data for 2a.
¹H NMR (300 MHz, CDCl₃): δ = 1.74-1.81 (ddd, 1 H, J = 7.9, 7.2, 6.3 Hz, H3β), 2.26-2.33 (ddd, J = 10.6, 6.3, 3.9 Hz, H3α), 3.24-3.32 (ddd, 1 H, J = 10.6, 7.9, 3.0 Hz, H1), 4.46-4.51 (ddd, 1 H, J = 7.2, 3.9, 3.0 Hz, H2), 7.18-7.21 (dd, 1 H, J = 8.5, 1.8 Hz, Ar-H), 7.44-7.52 (m, 2 H, Ar-H), 7.56 (br s, 1 H, H1′), 7.76-7.83 (m, 3 H, Ar-H).¹³C NMR (75 MHz, CDCl₃): δ = 18.7 (C3), 29.6 (C1), 61.6 (C2), 124.5 (Ar-CH), 125.5 (Ar-CH), 126.2 (Ar-CH), 126.6 (Ar-CH), 127.5 (Ar-CH), 127.7 (Ar-CH), 128.7 (Ar-CH), 132.7 (Ar-C), 133.1 (Ar-C), 133.6 (Ar-C). MS (EI): m/z (relative intensity) = 213 (24) [M⁺], 167 (100), 165 (53), 152 (33), 127 (15), 83 (13). R _f = 0.39 (10% EtOAc-hexane); mp 88-89 °C.
Spectroscopic Data for 2b.
¹H NMR (300 MHz, CDCl₃): δ = 1.67-1.74 (m, 1 H, H3α), 2.43-2.50 (ddd, 1 H, J = 9.0, 6.7 Hz, 4.2 Hz, H3β), 2.94-3.03 (m, 1 H, H1), 4.65-4.71 (ddd, 1 H, J = 8.3, 6.7, 4.2 Hz, H2), 7.35-7.38 (dd, 1 H, J = 8.3, 1.8 Hz, Ar-H), 7.41-7.50 (m, 2 H, Ar-H), 7.75-7.81 (m, 4 H, Ar-H). ¹³C NMR (75 MHz, CDCl₃): δ = 13.7 (C3), 28.7 (C1), 60.5 (C2), 126.2 (Ar-CH), 126.3 (Ar-CH), 126.7 (Ar-CH), 127.6 (Ar-CH), 127.8 (Ar-CH), 128.2 (Ar-CH), 128.4 (Ar-CH), 129.8 (Ar-C), 132.9 (Ar-C), 133.1 (Ar-C). MS (EI): m/z (relative intensity) = 213 (27) [M⁺], 167 (100), 165 (47), 152 (30), 127 (13), 83 (11). HRMS (EI): m/z calcd for C₁₃H₁₁NO₂: 213.0790 (-2.4 ppm); found: 213.0795. R _f = 0.27 (20% EtOAc-hexane).