NEW SYNTHETIC ROUTES TO 3-ARYL-2-CHLOROPYRIDINES, 5-ARYL-2-CHLOROPYRIDINES, AND 6-ARYL-2-CHLOROPYRIDINES

The efficient synthesis of 3-, 5-, and 6-aryl-2-chloropyridines via th e facile preparation of 5-(dimethyamino)aryl-substituted pentadienyl n itriles and cyclization with hydro chloric acid is described. This app roach allows for the introduction of other electron-withdrawing substi tuents on the pyridine ring as well as the preparation of the desired unsubstituted arylpyridines. Some differences in the rates of cyclizat ion of the pentadienyl nitriles as well as the yields of chloropyridin es were observed that depended on the position and degree of substitut ion in the aryl substituent. The arylpentadienyl nitriles 5 and 6 coul d also be converted directly into the corresponding 2-aminopyridines.