Trifluoromethyl substituted Delta(3)-imidazolines: Synthesis and reactivity

We describe the preparation of various 4-trifluoromethyl-substituted Delta(3)-imidazolines, which are precursors to amino acid-derived trifluoromethyl ketones. The imidazolines are prepared from alpha-silylimines and trifluoroacetonitrile by a 3+2 cycloaddition, and they can be hydrolyzed in weak acid to trifluoromethyl ketones. Additionally, we have identified several ring-opened compounds which result from treatment of the imidazolines with acid or base. Attempts to alkylate the imidazolines led to ring-opened products, so that the alkylation sequence ultimately produced N-alkylated amino acid-derived trifluoromethyl ketones. (C) 1997 Elsevier Science Ltd.