Easy and regioselective access to dimethyl acetal-protected heterocycles and their efficient allylation reactions mediated by allylaluminum reagent

Abstract

This paper describes easy access to twelve examples of five-and six-membered heterocycles (monocyclic and fused) containing a dimethyl acetal aldehyde function and/or a trifluoromethyl substituent, in good to excellent yields (72-98%). The dimethyl acetal-protected heterocycles were obtained in one-step via regioselective cyclocondensation reactions of 4,6,6-trimethoxy-1,1,1-trifluorohex-3-en-2-one with 1,2-, 1,3-and 1,5-dinucleophiles (hydrazines, hydrazides, hydroxylamine, 1-acetylguanidine and 1,8-diaminonaphthalene). Subsequently, to demonstrate a potential synthetic application, some pyrazole rings containing dimethyl acetal moiety were converted to the respective secondary homoallylic alcohols by efficient allylation reactions employing allylaluminum reagent in 84 to 90% yields.