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Three routes to [ [ 1-(trimethylsilyl)cyclopropyl]methylene]cyclohexanes and -2-cyclohexenes have been developed. The condensations of [ 1-(trimethyKiyl)cyclopropyl]lithium with cycloalkyl carboxaldehydes and of a-lithio selenides with 1-(trimethylsily1)cyclopropanecarboxaldehyde (10) are useful and complementary methods for gaining access to the methylenecycloalkanes. For more highly unsaturated systems, the methodology involving titanium-(0)-promoted coupling of 10 to cyclic a,@-unsaturated ketones is preferred. Silylcyclopropane 26 has been transformed into the racemic forms of a-vetispirene, hinesol, and @-vertivone. Ita broad utility resides in the ease with which desiliconation-alkylation of this substrate can be effected and the high regioselectivity of new carbon-carbon bond formation. Additionally, thermal rearrangement of the trimethylsilyl, (methoxydimethyl)carbinyl, and cyano derivatives invariably proceeds with preferential recombination of the respective biradical intermediate from that surface which is less sterically congested. As a result, the product mixtures are dominated by those stereoisomers suited for elaboration into the spirovetivane sesquiterpenes.Interest in the development of new syntheses of spirovetivane sesquiterpenes2 continues unabated. Because stereoselective construction of the spiro[4.5]decane carbon framework and regioselective introduction of at least one double bond comprise the essential elements of any successful approach, these requirements serve as an effective testing ground of new methodology. T h e feasibility of deploying preparative techniques involving nucleophilic cyclization,3 electrophilic cyclization,4 photochemical cy-(8) For example: (a) Conia, J. M. Bull. SOC. Chim. Fr. 1968,3057. (b) Conia, J. M.; Drouet, J. P.; Gorge, J.

Several methods for preparing bifunctional 1-(trimethylsilyl)-substituted cyclopropanes are described. The methyl bromide 4, available by Simmons-Smith cyclopropanation of 2 and bromination with phosphorus tribromide, is shown to be highly reactive to SN2 displacement and therefore easily transformed into a variety of other derivatives including the phenyl sulfide, phenyl sulfone, nitrile, and phenyl selenide. Ring-closure protocols have been applied to gain access to the triphenylphosphonium salt, phosphonate ester, and carboxaldehyde ( 22). The dimethyl acetal 23 of this aldehyde gives every indication of being an excellent conjunctive reagent as exemplified by its conversion to 24,26, and 30. Reactive anions of type A (X = S02Ph, SPh, SePh, CN) have been generated and in certain cases utilized for additional chemical transformations.Recent reports from these laboratories have described several synthetic2"4 and physical-organic studies5,6 involving silylcyclopropanes. In line with the recent general upsurge of interest in varied applications of organosilicon reagents,7 the boundaries of our previously limited knowledge of silyl-substituted small-ring compounds8 have begun to expand. The efficient preparation of this class of molecules remains, as always, the fundamental cornerstone of their broad-scale utilization. As a small contribution to this technology, we describe here synthetic approaches to a number of functionalized l-(trimethylsilyl)cyclopropanes with thé intent of illustrating their ready accessibility. Some chemical transformations of selected structures are also included to emphasize further

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The direct coupling of various aldehydes and ketones with CH2Br2 or CH2Cl2 promoted by TiCl4‐Mg bimetallic complex provides an extremely simple, practical, and efficient approach for the construction of bromomethyl or chloromethyl carbinols. The high chemoselectivity of this chemistry is illustrated by the TiCl4‐Mg‐promoted selective coupling of CH2Br2 or CH2Cl2 with an aldehyde in the presence of ketone and selective transfer of CH2Br or CH2Cl to saturated carbonyl moiety. This protocol is also suitable for sterically hindered and enolizable carbonyl compounds.

Aus den Cycloalkenyl‐cyclopropanen (I) entstehen bei der Gasphasen‐Pyrolyse die anellierten Verbindungen (II); analog reagiert (III) zum Cyclopenten (IV).

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Aus dem Trimethylsilylvinylbromid (I) erhält man über eine Grignardreaktion den Alkohol (II), der mit Methyleniodid zum Cyclopropan (III) reagiert und dann in das Bromid (IVa) übergeführt wird.