Catalysis of Organic..

386 Carbonylation of ChloropinacoloneA process which offers the opportunity to reduce the waste and eliminate theuse of hazardous solvents is the carbonylation of the commercially available α-chloropinacolone (1) (1-chloro-3,3-dimethyl-2-butanone). (See Reaction [1].)Unfortunately, earlier experience with the (Ph 3 P) 3 PdCl 2 catalyzed carbonylation ofα-bromopinacolone was not encouraging. (17) Consistent with the previouslyreported carbonylation of α-bromoacetophenone (18), the carbonylation of α-bromopinacolone gave low yields (64%) while demonstrating limited turnovernumbers (10 wt.% methyl pivaloylacetate and wasachieved in relatively short reaction times. These objectives would need to be metdespite addressing a more sterically challenging α-chloropinacolone substrate.This report will describe the realization of these goals by proper selection of thecatalyst and operating conditions, which ultimately led to a process with exceptionalturnover numbers (TON>10,000) and exceptional reactor productivities (productconcentrations >25 wt% in 3 hrs). Further, the process ultimately requires little or nosolvent while generating a benign NaCl waste stream.Results and DiscussionCatalyst Screening