Silicon-assisted synthesis of bridged azabicyclic systems via N-acyliminium intermediates

Abstract

Intramolecular acid-mediated reactions of 2-propynyl- and allylsilanes with five- and six-membered cyclic N-acyliminium ion precursors lead to bridged azabicyclic compounds (Table I). Neat formic acid is the reaction medium of choice in most cases. The cyclization reactions take place with complete regioselectivity. 2-Propynylsilanes are more reactive than allylsilanes. An ordinary olefin reacts poorly. The cyclization products can be useful for the synthesis of γ- and δ-amino acids and derivatives.