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 allen amines but possess comparable reactivity. Particularly, oxazolidinone and i midazolidinone substituted allenamides undergo efficient inverse demand [42] cycloaddition reactions with heterodienes, leading to unique pyranyl het erocycles. The reactivity differences between various allenamides containin g different substitution patterns around the nitrogen atom are illustrated. (C) 1999 Elsevier Science Ltd. All rights reserved.