AN IMPROVED SYNTHESIS OF 5-ALKYL-2,3-DIHYDRO-FURAN-2,3-DIONES

The synthesis of 5-tert-butyl-2,3-dihydrofuran-2,3-dione (2a) from ethenyloxysilane (3) and oxalyl chloride is reinvestigated. Apart from (2a), two other reaction products, namely furan-3-yl oxalate (6) and difuran-3-yl oxalate (7) are isolated, explaining the low yield of (2a) in this process. An improved method for the preparation of (2a), and its 5-methyl analog (2b) by cyclization of acylpyruvic acids (8a,b) is described