An Effective Use of Benzoic Anhydride and Its Derivatives for the Synthesis of Carboxylic Esters and Lactones:  A Powerful and Convenient Mixed Anhydride Method Promoted by Basic Catalysts

Abstract

Various carboxylic esters are obtained at room temperature in excellent yields with high chemoselectivities from nearly equimolar amounts of carboxylic acids and alcohols using 2-methyl-6-nitrobenzoic anhydride with triethylamine by the promotion of a basic catalyst such as 4-(dimethylamino)pyridine. A variety of lactones are also prepared in high yields at room temperature from the corresponding omega-hydroxycarboxylic acids with use of 2-methyl-6-nitrobenzoic anhydride in the presence of 4-(dimethylamino)pyridine. A similar reaction occurs with triethylamine when using a catalytic amount of 4-(dimethylamino)pyridine 1-oxide as an effective promoter for the intramolecular condensation reaction. These methods are successfully applied to the synthesis of erythro-aleuritic acid lactone and an eight-membered-ring lactone moiety of octalactins A and B. The efficiency of the cyclizations is compared to those of other reported lactonizations.

Total Synthesis of Thailandepsin B, a Potent HDAC Inhibitor Isolated from a Microorganism

“…The subsequent macrolactonization of 9 was achieved by employing the Shiina method [13][14][15][16][17] [2-methyl-6-nitrobenzoic anhydride (MNBA) (1.3 equiv), 4-dimethylaminopyridine (DMAP) (3.0 equiv), CH 2 Cl 2 (1.0 mM), rt, 12 h], which resulted in the desired cyclization product 17 in 85% yield. Finally, simultaneous S-Tr deprotection and internal disulfide bond formation in 17 (95%), followed by the deprotection of the TBS group in the resulting disulfide 18 (90%) furnished thailandepsin B (2) …”

Enhanced Structural Variety of Nonplanar <i>N</i>-Oxyl Radical Catalysts and Their Application to the Aerobic Oxidation of Benzylic C–H Bonds

“…The residue was purified with flash column chromatography (SiO 2 , n-hexane-EtOAc=4 : 4,5,6,7-Tetraf luoro-2-(4-methoxybenzyloxy)-3-(2,2,2-trifluoroethoxy)-3-trifluoromethylisoindolin-1-one (33) According to the procedure described for the preparation of ether 32 from alcohol 31 in which 2,2,2-trifluoroenthanol was used as the alcohol instead, alcohol 31 (1.00 g, 2.35 mmol) was converted into ether 33 (0.593 g, 50%). 35) b, 36) g, 37) h, 38) j, 39) and k 40) were prepared following the reported procedures. General Procedure for Benzoate from Alcohol (Procedure C) 3-(4-Methoxyphenyl)propyl Benzoate (36c) To a solution of 3-(4-methoxyphenyl)-1-propanol 42c (1.66 g, 10.0 mmol) in CH 2 Cl 2 (20 mL), BzCl (1.39 mL, 12.0 mol) and pyridine (1.93 mL, 24.0 mmmol) were added at 0°C.…”

Stereocontrolled Total Synthesis of Natural Products with Characteristic Molecular Structures and Biological Activities

“…Attempted macrolactonization using the Yamaguchi protocol furnished the requisite 140 in 56% yield for the two steps. After several attempts, it was found that the Shiina procedure 75,76) gave excellent results. Thus, treatment of a solution of 138 in CH 2 Cl 2 with 2-methyl-6-nitrobenzoic acid anhydride (139) and 4-dimethylaminopyridine (4-DMAP) at room temperature produced 140 in 92% yield.…”