TRIAZOLINES .30. NONREGIOSPECIFIC 1,3-CYCLOADDITION OF ARYL AZIDES TOVINYLPYRIDINES - A UNIQUE ROUTE TO PYRIDYL SUBSTITUTED AZIRIDINES .1.

The 1,3-cycloaddition of phenyl azides to the olefinic double bond of 4-vinylpyridine, yields the 1-phenyl-2-pyridylaziridine as the main pr oduct with only smaller amounts of the 1-phenyl-5-pyridyl-1,2,3-triazo line, although the reaction constitutes a general approach to the synt hesis of Delta(2)-1,2,3-triazolines. Experimental and theoretical evid ence are provided to explain the results on the basis that the olefini c bond in 4-vinylpyridine is an electron-deficient bond and that azide addition is not regiospecific. In the bidirectional addition reaction , the HOMOazide-LUMOolefin interaction predominates leading to a 1-phe nyl-4-pyridyl-1,2,3-triazoline, which, unlike the 5-pyridyl compound, loses nitrogen under thermal conditions to yield the aziridine, and at room temperature, a mixture of the respective triazole and the azirid ine.