Amine oxides. VIII. Medium-sized cyclic Olefins from amine oxides and quaternary ammonium hydroxides

Thermal decompositions of the N-oxides derived from N,N-dimethyl-1-methylcycloalk,lamines II having eight-, nine- and ten-membered rings yield olefin mixtures containing 98.6, 94.0 and 97.5%, respectively, of 1-methylcycloalkenes. Considerable amounts of the trans isomers are formed from the nine- and ten-membered N-oxides. Pyrolyses of the corresponding quaternary hydroxides produce mixtures of methylenecycloalkanes and 1-methylcycloalkenes (predominantly cis), violation of the Hofmann rule being at a maximum in the decomposition of the nine-membered quaternary hydroxide. Importance of relative product stabilities and the operation of non-bonded interactions are discussed as possible explanations for the observed directions of elimination. Thermal decompositions of the N-oxides and quaternary hydroxides of dimethylcycloalkvimethylamines IV containing eight-, nine- and ten-membered rings proceed as expected with formation of the corresponding methylenecycloalkanes.