Cycloadditionen mit dipolaren Zwischenstufen, II. Dipolare Produkte aus Allencarbonsäureestern

Abstract
Cycloadditions with Dipolar Intermediates, II. ‐ Dipolar Products from AllenecarboxylatesThe allenecarboxylates 2c‐c, and in some cases also the allenetri‐ and allenedicarboxylates 2d and 2e, f react with phosphanes, pyridines, and nucleophilic carbenes or their precursors to give the dipolar 1:1 adducts 10, 11 and 16,18, 20, respectively. These “carbene allene dipoles” represent stable derivatives of trimethylenemethane.