The reaction of ethyl chloroformate and pyridine with diethylaluminum
cyanide as the cyanide source gave the Reissert analog, 1-ethoxycarbon
yl-4-cyano-1,4-dihydropyridine and not the expected 1,2-dihydro regio
isomer. Under the same conditions, 3-bromopyridine also directly gave
the corresponding 1,4-dihydro Reissert analog. Reinvestigation of trim
ethylsilylcyanide, as the cyanide source, resulted in the observation
that both regio isomers are formed and the ratio of these isomers are
affected by both solvent polarity and by copper(I) iodide.