N-Pyridinium dichlorophosphinomethylides disproportionate to generate bis(N-pyridinium ylidyl)phosphenium chloride which undergoes 1,5-electrocyclization to give 2-phosphaindolizines. In one-pot synthesis N-(alkoxycarbonylmethyl)pyridinium bromide reacts with PCl3 in presence of Et3N to form 2-phosphaindolizine.