Reaction of essentially free benzyl cations with acetonitrile; synthesis of ethanimidic carboxylic anhydrides and unsymmetrical diacylamines

Ron W. Darbeau, Emil H. White, Nicholas Nunez, Brian Coit, Mark Daigle

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30 Scopus citations

Abstract

Benzyl cations were generated via the thermal decomposition of N-benzyl- N-nitrosopivalamide in acetonitrile and acetonitrile-water mixtures at 25 °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.

Original languageEnglish (US)
Pages (from-to)1115-1120
Number of pages6
JournalJournal of Organic Chemistry
Volume65
Issue number4
DOIs
StatePublished - Feb 25 2000

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

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