Electroreduction of (benzophenone)tricarbonylchromium and (fluorenone)tricarbonylchromium in the presence of electrophiles

Abstract

(Benzophenone)Cr(CO) 3 ( 2) and (fluorenone)Cr(CO) 3 ( 3) are reduced at a mercury pool cathode in aprotic media, in the presence of an electrophile which is more difficult to reduce. The results are compared with those which are obtained with the corresponding parent ketone. In the presence of 1,3-dibromopropane, a complexed olefinic alcohol 7a is the major isolated compound when 2 is the substrate, whereas a complexed spiro ether 8b is obtained with 3 as substrate. The electroreduction of 3 in acetonitrile in the presence of an equivalent amount of 4-chlorobutyryl chloride gives mainly the diacylated complex 10a. The unexpected formation of a nitrile complex 12a is also observed, which indicates an interaction between an intermediate species and acetonitrile. Complex 12a is obtained in low yield by the electroreduction of 3 in the presence of 3-bromopropionitrile. Under these conditions the major compound is (fluorenol)Cr(CO) 3.