Alkenyl silanes are efficiently converted to the corresponding silyl cyclopropanes in the presence of a slight excess of diazomethane (2-4 equiv) and a low loading of Pd(OAc)(2) (<0.5 mol %). Diazoethane and diazobutane can also be employed and yield silyl cyclopropanes with diastereoselectivities of up to 10:1 for the trans isomer. When conducted on a 4 g scale, the reaction only required a catalyst loading of 5x10(-3) mol %, which corresponds to a turnover frequency of 40,000 h(-1). Competition experiments revealed that vinyl silanes can be selectively cyclopropanated in the presence of an aliphatic terminal alkene and styrene. The complex [Pd(0) (2)(DVTMS)(3)] (38, DVTMS = divinyltetramethyldisiloxane) proved to be an exceptionally active catalyst for the cyclopropanation reaction, giving complete conversion at -35 degrees C in 1 min. Intermolecular and intramolecular competition experiments with DVTMS (36), both with Pd(OAc)(2) and 38, provided strong evidence for a Pd(0)(alkenyl silane)(3) resting state. Detailed density functional calculations on the reaction pathways for the cyclopropanation of trimethylvinylsilane and DVTMS by diazomethane with Pd(0) corroborated the experimental observations.

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Cyclopropane derivatives Q 0021Preparation and Applications of a Novel Bis(tributylstannyl)cyclopropane: A Synthetic Equivalent of a Cyclopropane-1,2-dianion. -A scalable synthesis of novel trans-1,2-bis-stannylcyclopropanes is developed. Its utility in tin-lithium exchange reactions is described. -(HEUREUX, N.; MARCHANT, M.; MAULIDE, N.; BERTHON-GELLOZ, G.; HERMANS, C.; HERMANT, S.; KISS, E.; LEROY, B.; WASNAIRE, P.; MARKO*, I. E.; Tetrahedron Lett. 46 (2005) 1, 79-83; Dep. Chim., Univ. Cathol. Louvain, B-1348 Louvain-la-Neuve, Belg.; Eng.) -Mais 16-065

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