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A full account of the Pd-catalyzed intramolecular reactions of (E)-2,2-disubstituted 1-alkenyldimethylalanes with aryl triflates as an entry into polycarbocyclic structures displaying an ethyl−methyl-substituted all-carbon benzylic quaternary center is herein presented. It was found that the efficiency of the Pd-catalyzed carbon−carbon bond forming process is highly affected by the structure of the starting material, including tether length and aryl substitution pattern; substituting the position ortho to the triflate is mandatory to obtain a good yield of the carbocycle. Moreover, the formation of 1-ethyl-1-methylindanes is facile in comparison to the case for the analogous tetrahydronaphthalenes, for which the competing methyl cross-coupling reaction is equally competent. It was established through labeling studies that the carbon−carbon bond forming events are stereospecific and proceed though the intermediacy of a neopentylic sp3-gem-dimetallic palladio(II) dialkylaluminoalkane species, from which a 1...

The ability to tune the reactivity of palladium carbenes derived from diphenylketene, which is dependent on the oxidation state of the metal center, is presented. Competition experiments illustrated that Pd(0) catalysts favor direct C−H functionalization of terminal alkynes and that Pd(II) catalysts lead to cyclopropanation of strained alkenes. In addition, a PdCl2-catalyzed cyclopropane isomerization of diphenylcyclopropanes and an unprecedented Pd(II)-catalyzed domino cyclopropanation/isomerization reaction are described.

The ambiphilic vinylcarbenoid reactivity of (α-(tributylstannyl)-π-allyl)palladium(II) species is demonstrated by the reaction of acetoxystannanes with Pd(dba)2, which promotes electrophilic metal−carbene reactions such as dimerization and cyclopropanation of strained alkenes. On the other hand, Pd(PPh3)4 and dppe revealed the nucleophilic nature of the dimetallic intermediates through sequential reactions of the carbon−metal bonds with dimethyl malonate.