Reactivity and selectivity of N-vinylic λ⁵-phosphazenes towards electrophiles. Synthesis of 2-aza-1,3-dienes

Abstract

The reactivity of the PN double bond of the N-vinylic λ5-phosphazene (1) towards several electrophiles is reported. Intermolecular aza-Wittig reaction of λ5-phosphazene (1) with aldehydes, phenyl isocyanate, and acid anhydrides leads to ethoxycarbonyl 2-aza-1,3-dienes (3), conjugated carbodi-imides (4), and N-protected amino acrylic acid derivatives (5), respectively, while the 2-azahexa-1,3,5-triene (8) and also the pyridine (7) are obtained when dienyl λ5-phosphazenes (6) are used. Reaction of λ5-phosphazene (1) with methyl iodide and acetyl chloride leads to N-alkylated (10) and N-acylated derivatives (11), respectively. Treatment of compound (11) in the presence of amino derivatives affords 1-amino-2-azabuta-1,3-dienes (14).