The mechanism of palladium(II) functionalization of various cycloalkanone oximes has been investigated. It was found that with 2,2-disubstituted cyclohexanone oximes, palladium inserted into methyl groups exclusively in preference to allyl-, and benzyl-groups. Oximes without a methyl group in an equatorial orientation, and cycloheptanone and cyclooctanone oximes, all formed a presumed polymeric species which was not fully characterized. Large primary and secondary deuterium kinetic isotope effects (--4 and ~1.2 respectively) were measured in the palladium functionalization of the 2,2-dimethylcyclohexanone oxime system.
The mechanism of palladium(II) mediated demercuration of various cycloalkyland cycloalkylmethylmercuric chlorides has been found to change as a function of ring size. The mechanism for demercuration in the cyclohexylmethyl system, which involves the elimination/readdition of [HPdX], was established by extensive deuterium labelling experiments, and replaces a previously proposed mechanism. The cyclooctyland cyclooctylmethyl systems exhibit a different mechanism involving carbocation formation, while the cycloheptyl- and cycloheptylmethyl systems show evidence of a blend of both mechanisms.
The reactivities of six to nine membered ring cycloalk-1-enylsilanes and 1,2- epoxycycloalkylsilanes have been investigated following reports of unusual mechanisms leading to trans-cyclooctenes. Careful examination of the products show that these reactions have a marked dependence on ring size. The mechanisms of some of these reactions have been clarified by the use of deuterium labelled analogues, demonstrating the unimportance of several proposed mechanisms.