Olefin Cross-Metathesis of Alkenyl Epoxides with Allyl- and Vinyl-trimethylsilane

Abstract

The first olefin cross-metathesis reactions of alkenyl epoxides with allyltrimethylsilane and trimethylvinylsilane are reported. The products represent useful synthetic building blocks in Lewis acid mediated cyclization and condensation reactions.

Key words

allylsilanes - catalysis - cyclizations - epoxides - metathesis

References

• 1 Review: Schuster M. Blechert S. Angew. Chem. Int. Ed. Engl.   1997,  36:  2036 . Angew. Chem.  1997,  109:  2124 
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• Reviews:
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• For intramolecular reactions of epoxides with allylsilanes, see:
• 4a Procter G. Russell AT. Murphy PJ. Tan TS. Mather AN. Tetrahedron  1988,  44:  3953 
• 4b See also: Armstrong RJ. Weiler L. Can. J. Chem.  1986,  64:  584 
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6

Typical Procedure: A CH₂Cl₂-solution (7 mL) of 1 (126 mg, 1.1 mmol) and 2a (98 mg, 1.0 mmol) was degassed (argon). A CH₂Cl₂-solution (8 mL) of Grubb’s catalyst (41 mg, 5 mol%) was added and the solution was stirred under reflux for 8 h and at 20 °C for 16 h. The solvent was removed in vacuo and the residue was purified by column chromato-graphy (silica gel, ether/petroleum ether = 1:5) to give 3a (62 mg, 34%) and 4 (41 mg, 49%) as colourless oils. Spectroscopic data of 3a: ¹H NMR (CDCl₃, 250 MHz):
-0.03, -0.01 (2 × s, 9 H, SiMe₃), 1.35-1.70 (m, 4 H, CH₂), 2.10-2.20 (m, 2 H, CH₂), 2.45-2.55, 2.75-2.80, 2.90-3.00 (3 × m, 3 × 1 H, O-CH, O-CH₂), 5.20-5.35, 5.35-5.50 (2 × m, 2 × 1 H, HC=CH). ¹³C NMR (CDCl₃, 62.5 MHz): -2.09, -1.89 (SiMe₃), 18.39, 22.53, 23.44, 29.15, 32.55, 32.88 (CH₂), 47.09 (OCH₂, both isomers), 51.86, 51.94 (O-CH), 125.90, 126.38, 127.01, 127.30. MS (70 eV): m/z = 184 (2) [M⁺], 169 (1), 155 (1), 129 (9), 115 (12), 73 (100); the exact molecular mass for C₁₀H₂₀OSi m/z = 184.1283 ± 2 mD [M⁺] was confirmed by HRMS (EI, 70 eV). All new compounds gave satisfactory spectroscopic and analytical and/or high resolution mass data.