Methyl orthobutyrate

Orthoesterification A mixture of 1 g of 6a a-difiuoroprednisolone, 10 mg of p-toluene-suifonic acid, 5 cc of dimethylformamide and 3 cc of methyl orthobutyrate is heated for 15 hours on an oil bath at 105°C while a slow stream of nitrogen is passed through the mixture so that the methanoi produced as a by-product of the reaction, is distilled off. After addition of severai drops of pyridine to neutralize the acid catalyst, the reaction mixture is evaporated under vacuum and there is obtained a solid residue which is taken up with methanol, and filtered. The product is recrystailized from a methylene chloride-methanol mixture to yieid 682 mg of 6a,9af[Pg.491]

Ethyl orthobutyrate added at room temp, to a soln. of 4-(2-hydroxy-1-methyl-propyl)-3-methyl-y-resorcyclic acid in ethyl acetate, and the product isolated after 2 hrs. 1-propylcitrinin. Y 66%. F. e. s. H. H. Warren, M. Finkelstein, and D. A. Scola, Am. Soc. 84, 1926 (1962). 

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