Inverse demand [4+2] cycloaddition reactions of allenamides: Reactivity scopes of an electron deficient variant of allenamines

The synthesis and reactivity of a series of new allenamides are described. These electron deficient variants of allenamines are more stable than allenamines but possess comparable reactivity. Particularly, oxazolidinone and imidazolidinone substituted allenamides undergo efficient inverse demand [4+2] cycloaddition reactions with heterodienes, leading to unique pyranyl heterocycles. The reactivity differences between various allenamides containing different substitution patterns around the nitrogen atom are illustrated.