Transformations of the dihydropyridine ring system.

The reaction of a 4-chloromethyl-1,4-dihydropyridine with potassium cyanide has been investigated, and in this respect it has been found to behave analogously to other 4-chloromethyl-1,4-dihydropyridines. However, on treatment with water, a unique transformation, affording a dihydrofuran, demonstrated that the 4-chloromethyl-1,4-dihydropyridine was considerably more reactive than the other 4-chloromethyl-1,4-dihydro-pyridines which did not undergo analogous transformations. An attempt to rationalize this has been made, and a mechanism suggested for the formation of the 2,3-dihydrofuran. Evidence for the structure of the 2,3-dihydrofuran is presented. Some reactions of the compound have been investigated, including rearrangement to a fulvene derivative and degradation to 3,3-diacetylpropionaldehyde. The tautomerism of the latter compound is discussed in detail, and a synthesis described