Friedel-Crafts chemistry of dieneiron tricarbonyl complexes. Acetylation of 1-silylated and 1,4 disubstituted dienes

In contrast to simple olefinic or to aromatic compounds bearing a silyl group attached to an sp² carbon, trimethyl-silylated dieneiron tricarbonyl complexes, do not undergo ipso-substitution reactions unless there is an alkyl group in the 4 position. This allows synthesis of acylated dienes that still retain the Me₃Si substituent. In one case an unusual 1,1-diacylation was observed during an attempted single acetylation. 1,4-Disubstituted dieneiron tricarbonyl complexes were found to give good yields of stable acylated complexes under the usual Friedel-Crafts conditions.