Substituent Effects on the Regioselectivity of Intramolecular Carbene C-H Insertion. Cyclizations of 1- and 5-Substituted 2-Adamantylidenes

Article abstract of DOI:10.1021/jo00134a005

Carbenes, 1-methyl-, 1-chloro-, 5-methyl-, and 5-chloro-2-adamantylidene, were generated by pyrolysis of dry tosylhydrazone alkali salts.Each of these carbenes yielded both possible products of the intramolecular C-H insertion, the corresponding 1- and 3-substituted 2,4-didehydroadamantanes or 1- and 7-substituted 2,4-didehydroadamantanes.The product distribution varies considerably depending on the substituent and its position relative to the carbenic center.The results indicate that the regioselectivity of the intramolecular carbene C-H insertion is sensitive to very small changes in geometry and electron distribution in the system.