Chain-extension reactions of aeetylenes. Part 4. Reaction of 1,3-dilithioacetylides with carbonyl electrophiles, hexamethylphosphoric triamide, and benzylideneaniline

Abstract

The regioselectivity of the reactions of 1,3-dilithioalk-1-ynes with various electrophiles has been examined. With formaldehyde and cyclic ketones, reactions occur both at C-1 and C-3 to give alk-2-yne-1,5-diols. In contrast reactions with carbon dioxide give allene-1,3-dicarboxylic acids.

1,3-Dilithioalk-1-ynes decompose hexamethylphosphoric triamide and the resulting N-methylmethyleneamine undergoes addition only at the propargylic site. Further reaction with either 1-bromobutane or water gives alkynylamines. Benzylideneaniline also reacts with 1,3-dilithiohex- and hept-1-ynes only at the propargylic site to give N-phenylbut-3-ynylamines.