ALPHA,BETA-DICYANOSTILBENE FROM PHENYLETHYNYL AZIDE AND FROM PHENYLETHYNYL ISOCYANATE

The formation of dicyanostilbene 12 from an adduct 1 composed of equimolar amounts of phenylethynyl bromide and iodine azide, from 2-phenyl-3-bromotriazole 13, and from phenylpropiolyl azide 15 is accounted for by photodimerization with loss of nitrogen or carbon monoxide from phenylethynyl azide 9 or phenylethynyl isocyanate 16, as appropriate. Both 9 and 16 are assumed intermediates and 12 is transformed into 9,10-dicyanophenanthrene 14. Intermolecular abstraction and insertion products for phenylcyanocarbene were photolytically obtained from both 13 and 15 but not from 1. Accordingly interaction between the carbene and its precursors 9 and 16 provides an alternative mechanism, indistinguishable from dimerization of either 9 or 16, to account for 12 from both 13 and 15 but not from 1. A minor product, methyl benzoate, from the photolysis of 1 in methanol apparently is derived from 2-bromo-2-iodo-3-phenylazirine 11. In dark reactions several reagents including alumina, magnesium, zinc, and thiourea, transformed 1 into 12, with 9 as an assumed intermediate. There was no evidence for the intermediacy of either phenylcyanocarbene or phenylethynylnitrene. © 1969, American Chemical Society. All rights reserved.