Discussion It is interesting to note the difference between the cyclization of the foregoing 1, 4- dibromo ketones to dihydro-1, 4-pyrans and the formation of cyclobutane derivatives from cy, a'-dibromoadipic esters. The latter case corresponds to carbon alkylation and the former to oxygen alkylation. The fist step in the reaction may be represented as the replacement of one bromine atom by a cyano group, yielding a compound of the type of Ia. By enolization ...
