反应详情

The prior art preparation of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxamides (Ia) has been effected by two methods. The first method has included (1) converting acetoacetamide to alphachloroacetoacetamide, (2) reacting this with 2-mercaptoethanol in a mutual solvent in the presence of a base, (3) subjecting the resulting product to acidic conditions whereby it cyclizes with loss of water to form 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxamide (Ia) and (4) isolating said product from the reaction mixture. The second method of preparing same has used alkyl acetoacetate in place of acetoacetamide as a starting material. Thus, from the procedure analogous to the first method described above, the resulting 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboalkoxide (Ib) was converted to 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxamide (Ia).