title: Reaction of essentially free benzyl cations with acetonitrile; synthesis of ethanimidic carboxylic anhydrides and unsymmetrical diacylamines
abstract: Benzyl cations were generated via the thermal decomposition of N-benzyl-N-nitrosopivalamide in acetonitrile and acetonitrile-water mixtures at 25 degrees C. The first-formed (primary) benzylating agent, the benzyl cation, was scavenged competitively by pivalate (trimethyl acetate) ion to yield benzyl pivalate, by acetonitrile to yield the corresponding N-benzylnitrilium ion, and by water (when present) to yield benzyl alcohol. The nitrilium ion underwent a cascade of reactions to yield an array of products whose identities and relative yields as a function of time were used to elucidate the mechanistic paths involved. Thus, the N-benzylnitrilium ion reacted with pivalate ion to yield the Z-isomer of N-benzylethanimidic pivalic anhydride, followed by its conversion into the E-isomer. This article appears to be the first to document compounds of this type. The E-isomer is labile under the reaction conditions, rearranging into N-acetyl-N-pivalylbenzylamine. In the presence of water as a diluent, a significant fraction of the nitrosoamide was hydrolyzed to benzyl alcohol; hydrolysis of the nitrilium ion yielded N-benzyl acetamide. The yield of hydrosylates was directly proportional to the mole fraction of water in the medium.
authors.affiliation: Departments of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 and The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.initials: RW
authors.lastname: Darbeau
authors.initials: EH
authors.lastname: White
authors.initials: N
authors.lastname: Nunez
authors.initials: B
authors.lastname: Coit
authors.initials: M
authors.lastname: Daigle