Cyclobutane dicarboxylic acid, decarboxylation

Decarboxylation reactions of cyclobutanecarboxylic acids appear to pose no particular problems. Cyclobutane-1,1-dicarboxylic acids can usually be decarboxylated thermally at temperatures up to 200 C.1 5> n 340 For example, cyclobutane-1,1,3,3-tetracarboxylic acid was heated to 185 °C at reduced pressure to give a mixture of cis- and frani-cyclobutane-l,3-dicarboxylic acid (l).1 Noteworthy in this reaction is the stereocontrof obtained in the product due to the formation of the anhydride. Generally, decarboxylation will give a mixture of cis- and transacids. The decarboxylation has sometimes been performed in a distillation step.4,5... 

This reaction was initially reported by Franchimont in 1872. It is a condensation of two a-bromocarboxylic acids in absolute alcohol in the presence of sodium cyanide to give 1,2-dicarboxylic acids after hydrolysis and decarboxylation. In the case of a-bromoketones, 1,4-diketones are produced similarly after hydrolysis with phosphoric acid. It was found that the bulky group at the ester end prevents condensation, as in the case of phenyl and naphthyl esters. Although the substituent at j0-position does not prevent such condensation, it reduces the overall yield. In addition, a compound with two ester groups at proper position will form cyclic diacid under such reaction conditions and cyclobutane, " cyclopentane and cyclohexane dicarboxylic acid have been prepared in such a way. In the case of l,4-dibromo-l,4-dibenzoylbutane, a derivative of cyclopentanone is produced after acidic hydrolysis. It should be pointed out that other common solvents—including acetone, ether, and acetonitrile- are not good for this reaction. ... 

Reaction of malonic esters with 1,2-dibromoethane and 1,3-dibromopropane under liquiddiquid two-phase conditions produces the cyclopropane- and cyclobutane- 1,1 -dicarboxyl ic esters, which can be hydrolysed under the basic conditions (6.2.24.C) [e.g. 75, 109] and decarboxylated to give the monocarboxylic acid [e.g. 109]. 

Decarboxylation can be accompanied by hydrolysis in a one-pot reaction as in the formation of cyclobutanecarboxylic acid from diethyl cyclobutane-1,1-dicarboxylate.4... 

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