Acetylenedicarbaldehyde: isolation and some examples of exclusive dienophilicity under neutral conditions

Abstract

Acetylenedicarbaldehyde (1) is isolated in the pure state after acidolysis of its monoacetal (2) with an excess of formic acid followed by dehydration of residual HCO₂H into CO with P₂O₅; under neutral conditions, (1) reacts with conjugated dienes as a dienophile only, in contrast to what occurs in acidic medium.