Recently we have reported several synthetic approaches to branched triangulanes (oligoepiroalkanes consisting only of three-membered rings).1,2 Unfortunately, most of these are rather complicated multistep syntheses. The most convenient approach is based on a methodology previously used in the synthesis of unbranched triangulanes,3•4 i.e. cycloaddition of (chloromethyl)carbene to an appropriate bicyclopropylidene,5 dehydrochlorination with potassium feri-butoxide in DMSO,1'5 and finally cyclopropanation with diazomethane under palladium(II) acetate catalysis.1"6 However, the inaccessibility of higher oligospirocyclopropane-annealated bicyclopropylidenes is an essential limitation of this approach. We have therefore developed a new methodology, which is widely applicable to unsubstituted bicyclopropylidene7"9 as well as spirocyclopropanated bicyclopropylidenes. Results and DiscussionAs recently reported10 *a number of methyl carboxylates react with ethylmagnesium bromide in the presence of tetraisopropoxytitanium to form 1-substituted 1-cyclopropanols. We have now found that this reaction is also applicable to methyl cyclopropanecarboxylate (1) and gives 1-cyclopropyl-1-cyclopropanol (2) in almost quantitative yield. Adopting our previous experience,8•9 it is now possible to prepare bicyclopropylidene (4) in synthetically useful quantities of 40-45 g within 1 week (Scheme I).11 * Author to whom correspondence should be addressed. t Dedicated to Professor Klaus Hafner on the occasion of his 65th birthday.

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