Abstract
In 1967 we synthesized the first phosphabenzene with tervalent P, coordination number 2, and a 3pπ-2pπ-P[dbnd]C-double bond: the 2,4,6-triphenylderivative.1 One of the challenging problems in synthetic organic chemistry - is it possible to replace in the benzene molecule one of the carbon atoms by a second or third row element, by Si, P, As; is it possible to synthesize - against the classical octet rule - Phospha-, Arsa- or Sila-benzenes, had been solved in principle for the element P. This first synthesis was carried out by reaction of pyrylium salts with P (CH2 OH)3 in refluxing pyridine (Fig. 1).