Silanes in Organic Synthesis. 10. Cleavage Reactions of Silylcyclopropanes with Titanium Tetrachloride and Hydrogen Chloride

Article abstract of DOI:10.1021/jo00327a013

Seven trimethylsilyl-substituted cyclopropanes, both mono- and bicyclic, were treated with titanium tetrachloride and anhydrous hydrogen chloride to determine the regioselectivity and stereoselectivity of electrophilic attack on their strained three-membered ring.Whereas cleavage of exo-6-(trimethylsilyl)bicyclo<3.1.0>hexane with TiCl4 occurs predominantly at the zero bridge, the principal product obtained from treatment with HCl is the result of peripheral bond scission.In the case of exo-7-(trimethylsilyl)bicyclo<4.1.0>heptane, addition to an edge bond occurs regiospecifically with both reagents.Substrates 11 and 12 were examined to assess the importance of carbonium ion intervention.Structural isomerizations mediated by such intermediates were observed with both silylcyclopropanes.For 1-(trimethylsilyl)bicyclo<4.1.0>heptane and 1-(trimethylsilyl)-1-pentylcyclopropane, the altered position of the silicon substituent was seen to have a major effect on the course of ring opening.Although the present data allow some analogies to be drawn with vinylsilanes, it is clear that silylcyclopropanes have a broader range of reaction pathways available to them than do their olefinic counterparts.