Reaction of (Z)-β-enamino λ5-phosphazenes and dimethyl acetylenedicarboxylate

Abstract

N-Phenyl-β-enamino λ⁵-phosphazenes (1) react with dimethyl acetylendicarboxylate to give stable 1 : 1 adducts (2). The enamine moiety of the functionalised phosphonium ylides (2) displays ambident nucleophility; thus, heating of compounds (2) results in N-cyclocondensation, affording 1-aza-4λ⁵-phosphinines (3), while 1-aza-2-oxo-4λ⁵-phosphinines (5) and enamino λ⁵-phosphole derivatives (4) are obtained when adducts (2) are treated with KH and BuLi, respectively. The reaction of N-ethoxycarbonyl- and N-benzoyl-β-enamino λ⁵-phosphazenes (6) and (7) with the dicarboxylate, however, involves the C_β–H enamino bond, affording phosphorylated 2-pyridones (10) and (11).