Universal Method for the Functionalization of P-Bromovinyl Trifluoromethyl Ketones of Cyclobutene Series

摘要

Unsaturated trifluoromethyl ketones are a new extremely promising class of compounds whose properties in recent two decades have been intensively studied in medicine [1], biochemistry [2], and molecular biology [3]. Moreover, these compounds are widely used in organic synthesis [4]. It is of special synthetic interest to use unsaturated trifluoromethyl ketones containing a leaving group in the β position, whose structural features provide a possibility to carry out functionalization reactions and to synthesize different fluorine-containing heterocyclic compounds [4]. However, these transformations have hitherto been studied only for the simplest acyclic β-substi- tuted fluorine-containing enones [5], whereas similar enones with the C=C bond being incorporated into a strained small ring have been unknown until recently. Very recently, we found an unusual reaction of [2+2] cycloaddition of l-trifluoroacetyl-2-haloacety-lenes to simple alkenes that proceeded in the absence of light and catalyst to give β-halovinyl trifluoromethyl ketones of cyclobutene series [6, 7]. With the use of corresponding bromides 1a-1f, we attempted to develop a general method for the displacement of bromine atom by different aryl and hetaryl substituents to form new β-arylvinyl trifluoromethyl ketones of cyclobutene series.