Benzoic isobutyric anhydride hydrolysis

Catalysis of the synthesis of benzoic anhydride and the hydrolysis of benzoyl chloride, diphenyl phosphorochloridate (DPPC), and benzoic isobutyric anhydride in dichloromethane-water suspensions by water-insoluble silanes and siloxanes, 3- and 4-trimethylsilylpyridine 1-oxide (3b and 3c, respectively), 1,3-bis(l-oxypyridin-3-yl)-l,1,3,3-tetramethyldisiloxane (4), and poly[methyl(l-oxypyridin-3-yl)-siloxane] (5) was compared with catalysis in the same systems by water-soluble pyridine 1-oxide (3a) and poly(4-vinylpyridine 1-oxide) (6). All catalysts were effective for anhydride synthesis and promoted the disproportionation of benzoic isobutyric anhydride. Hydrolysis of benzoyl chloride gave benzoic anhydride in high yield ( 80%) for all catalysts except 3a, which gave mixtures of anhydride (52%) and benzoic acid (39%). The order of catalytic activity for DPPC hydrolysis was 5 > 4 > 3b > 3a > 3c > 6. The results suggest that hydrophobic binding between catalyst and lipophilic substrate plays an important role in these processes. 

Hydrolysis of Benzoic Isobutyric Anhydride. Reactions of mixed anhydrides can be complicated by disproportionation reactions (equation 10). The process may be operative in any investigation of anhydride hydrolysis, but it would go undetected in studies with symmetrical anhydrides or in studies that just monitor reaction rates by consumption of base. To obtain a more complete understanding of the catalytic behavior of 3, 4, 5, and 6 in transacylation reactions, the hydrolysis of benzoic isobutyric anhydride was investigated. 

NMR analysis was used to fully characterize product mixtures, because the chemical shifts of aliphatic protons are different for benzoic isobutyric anhydride and isobutyric anhydride, a possible disproportionation product (36). The results are given in Table IV. In all cases, disproportionation accompanied the hydrolysis of benzoic isobutyric anhydride in stirred suspensions of dichloromethane-0.5 M aqueous sodium bicarbonate. All catalysts behaved similarly, despite the major solubility differences of 3a and 6 versus 3b, 3c, and 5. For the hydrolysis of benzoic isobutyric anhydride, as with the other studies described in this report, 1-oxypyridinyl-substituted... 

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