Syntheses and 1,3-dipolar cycloaddition reactions of benz[de]isoquinolinium-1-ides

Abstract

Benz[de]isoquinoliniurn-1-ides prepared in situ by treatment of 2-substituted 2,3-dihydro-1H-benz[de]isoquinoline N-oxides with acetic anhydride, reacted with dimethyl acetylenedicarboxylate and with maleimides to give 1 : 1 cycloadducts. The stereochemistry of the maleimide cycloadducts was determined by n.m.r. spectroscopy. Exclusive or predominant formation of the endo-adducts is in sharp contrast with the case of naphtho[1,8-cd]-thiopyran, which reacts with maleimides to give exclusively or predominantly exo-adducts The adducts were converted into cyclohepta [de]naphthalene derivatives.