Spiro(3,3)heptane. The Hunsdiecker Degradation of Carboxylic Acids

A general method for the synthesis of polyspiranes containing cyclobutane rings is described. The method involves condensation of sodiomalonic esters with derivatives of trimethylene glycol to give cyclobutane-1,l-dicarboxylates, reduction of these esters with lithium aluminum hydride to the corresponding 1,1-dimethylol cyclobutane, and the use of this substituted trimethylene glycol tor a repetition of the cycle. By means of this series of reactions, spiro-(3,3)-heptane has been made. The degradation of silver salts of certain types of aliphatic oarboxylle acids with bromine has been investigated. Halogen-substituted acids were found to give results that were dependent upon the position of the halogen and the technique that was employed. Polycarboxylic acids, contrary to some previous reports, were found to undergo the reaction in fair yields, giving alkyl polybromides. The cyclobutane ring was found to be cleaved during the degradation if carried out as customarily described, but use of low temperature techniques gave cyclobutyl bromides in good yields. The mechanism of the reaction is the subject of some speculation, but its synthetic usefulness seems considerable.