Access to phosphacymantrene-2-carboxylic acid and 2-carboxaldehyde derivatives

Two new approaches to alpha-functional phosphacymantrenes are described. Th e reaction of [Mn-2(CO)(10)] with a phosphole-2-carboxylate affords the cor responding phosphacymantrene-2-carboxylate 2. Replacing one carbonyl by one triphenylphosphine on manganese enhances the reactivity of phosphacymantre nes toward electrophilic substitution. Thus, a Vilsmeier formylation leadin g to a phosphacymantrene-2-carboxaldehyde such as 5 becomes possible. The r eduction of 5 affords the corresponding primary alcohol 6 and the methyl de rivative 7.