Cyclopropyl compounds palladium catalyzed

With palladium catalysts, such as bis(dibenzylideneacetone)palladium/triisopropylphosphane (1 1) or tris(acetylacetonato)palladium/triisopropylphosphane/ethoxydiethylaluminum (1 1 2), 3,3-dimethylcyclopropene can be reacted in methyl acrylate as solvent to yield small amounts (about 10%) of cotrimers constisting of two molecules of the cyclopropene and one molecule of methyl acrylate, namely, a 1 1 mixture of methyl 3-[2,2-dimethyl-3-(2,2-dimethyl-cyclopropyl)cyclopropyl]prop-2-enoate isomers 40 and methyl 3,3,8,8-tetramethyltri-cyclo[5.1.0.0 ]octane-5-carboxylate (41). These compounds can be obtained in far better yield using trialkylphosphane-modified nickel(O) catalysts (see above). Major products of the palladium-catalyzed reaction are the homo-cyclodimer, 3,3,6,6-tetramethyl-exo-tricy-clo[3.1.0.0 ]hexane (55%), and the homo-cyclotrimer, 3,3,6,6,9,9-hexamethyl-crtt/o,e.TO-tetra-cyclo[6.1.0.0 - .0 ]nonane (33.5%). 

Cyclopropanation of alkenes can also be accompUshed via other transient electrophilic intermediates that are possibly metal complexes of carbenes. Copper, rhodium, ruthenium, cobalt, or palladium catalyze the decomposition of diazocarbonyl compounds [62] which, in the presence of alkenes, gives cyclopropyl derivatives. The intramolecular example shown in Equation 7.37 uses rhodium bis(l-adamantate) dimer as the catalyst [63]. 

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