Mechanistic Duality in Tertiary Amine Additions to Thermally Generated (HDDA) Benzynes

摘要

Reported here are studies directed at understanding the mechanism of tertiary amine addition to hexade-hydro-Diels-Alder (HDDA)-generated benzynes. Tertiary amines are presumed to engage benzynes by generation of a zwitterionic intermediate. Simple trialkylamines undergo intermolecular protonation by a protic nucleophile to give an aryl ammonium intermediate that is then dealkylated. Amines containing acidified β-protons undergo an intramolecular elimination to give the aniline and an alkene. Finally, aminoalcohols react at either of their N- or O-atoms, depending upon the extent of internal hydrogen bonding.