An industrially usable Pd-catalyzed carboalkoxylation of 1,2-dibromo-3,3,3-trifluoropropane to tert-butyl trifluoromethacrylate in the presence of an inorganic base

Pd-catalyzed carboalkoxylation of 1,2-dibromo-3,3,3-trifluoropropane 1 with tert-butyl alcohol to provide tert-butyl trifluoromethacrylate was improved from a practical standpoint. The addition of an inorganic base, specifically Li2CO3, surmounted the previous disadvantages of low reactivity and selectivity. Li2CO3 not only accelerated the reaction drastically but also suppressed the further reaction of the methacrylate and alcohol completely. It is suggested that the role of Li2CO3 is to stabilize an acylpalladium tert-butoxide intermediate, while HBr and/or H+ were scarcely abstracted from the substrates by Li2CO3. Research on the optimal conditions resulted in a satisfactory yield (ca. 70%) of tert-butyl trifluoromethacrylate under mild conditions (CO 10 atm, 100 °C and 15 h) in ethyl acetate solvent with 0.05 mol% PdCl2(PPh3)2. This carboalkoxylation was also usable for other bulky alcohols.

Graphical abstractPd-catalyzed carboalkoxylation of 1,2-dibromo-3,3,3-trifluoropropane with tert-butyl alcohol to provide tert-butyl trifluoromethacrylate was improved from a practical standpoint. The addition of an inorganic base, specifically Li2CO3, surmounted the previous disadvantages of low reactivity and selectivity. Li2CO3 not only accelerated the reaction drastically but also suppressed the further reaction of the methacrylate and alcohol completely. Figure optionsDownload full-size imageDownload as PowerPoint slide