Recently Krapcho and Lovey have reported that germinal diesters, B-keto esters and a-cyano esters undergo decarbalkoxylatlons when heated with sodium chloride In wet dimethyl eulfoxide at temperatures of 140-185' (1). We now wish to report further experiments addressed to the question of whether added NaCl is necessary in this reaction or whether water alone is sufficient to effect the decarbalkoxylation process. The substrates investigated along with the experimental conditions and results are tabulated in Table I.
Let ua examlne home of the pertinent results which can be found in the Table . The decarbalkoxylatlons of 2-carbalkoxycyclohexanone (entry 1, mixed methyl and ethyl esters) and I-carbethoxpcyclooctanone (entry 2) proceed readily in DMSO-R20. After 3 hrs of heating good yields of cyclohexanone and cyclooctanone can be isolated. The decarbalkoxylation of 2-carbalkoxycyclohexanone also occurs in DMF-H20 although at a slower rate than in DMSO-H20. This presumably merely reflects the lower reaction temperature attainable In the DMF-H20 medium.
Diethyl phenylmalonate (entry 3) on heating in DMSO-H20 undergoes a facile decarbethoxylation to produce ethyl phenylacetate in an excellent yield. In order to assess the effect of added NaCl on the decarbethoxylation of this dlester duplicate runs were perfofiled simultaneously In the presence and absence of NaCl. The progress of the reaction was monitored by nmr analysis and the reaction proceeds at nearly the same rate in the two runa. In this case the presence of NaCl has practically no effect on the decarbethoxylation rate.