Polyhalogenoaromatic compounds. Part XIII. The reduction of pentachloropyridine and derivatives with lithium aluminium hydride and other complex metal hydrides

Abstract

The formation of 2,3,6-trichloropyridine, the main product from the reduction of pentachloropyridine with lithium aluminium hydride in ether has been rationalized on the basis of addition of AIH4– across the 3- and 4-positions of the pyridine ring followed by an unusual cis-elimination. Analogous mechanistic schemes explain results obtained from reduction with lithium aluminium hydride of several substituted polychloropyridines. Pentachloropyridine has also been reduced with sodium and lithium borohydrides, diborane, and aluminium hydride.