Synthesis of Cyanodienes and. Their Photosensitized Dimerization

Abstract

A novel synthetic method of cyanqdienes (2, 4-pentadienenitriles) from 1, 4-dibromo-2-butenes was found.1, 4-Dibromo-2-butenes (1 mol) was treated with 1.2 mol of potassium cyanide and 1.2 mol of potassium hydroxyde in a water-acetone mixture.1-Cyanobutadiene C 1 J was obtained from 1, 4-dibromo-2-butene (71%, Table 3). From 2-methyl-1, 4-dibromo-2-butene, the mixture of 1- and 4-cyanoisoprene [2 and 3] was obtained (91%, [2]/[3]=22/78, Table 4). The photosensitized dimerizations of the above nitriles were also studied. Each dimerized product by these reactions had a six-membered ring. Furthermore, in the presence of radical trapping reagents, the reactions were retarded. Therefore, these reactions seem to proceed on the stepwise radical mechanism.