STUDIES ON O-ACYLATION AND N-ACYLATION OF 3-HYDROXYISOXAZOLE AND THEIR REGIOSELECTIVITY .2. REGIOSELECTIVE SYNTHESIS OF O- N-ACYLATION PRODUCTS OF 5-METHYL-3-HYDROXYISOXAZOLE/

The acylation of 5-methyl-3-hydroxyisoxazole (1) with 3-methyl-2-(4'-c hlorophenyl) butyryl chloride (2a) has been studied under different re action conditions. synthetic methods, solvents, acid-binding agents an d reagent stoichiometry exhibit significant influence on the ratio of O-/N-acylation products of 1. O- or N-regioselective acylations of 1 h ave been developed. Acylation of 1 in the Presence of triethylamine in acetonitrile yielded O-acylated regioisomers 3a similar to 3e with co ntent 88 similar to 96%. The trimethylsilyl enol ether of 1 reacted wi th acid chloride 2a similar to 2i in benzene to afford N-acylated regi oisomers 5a similar to 5i with content 86 similar to 96%. It was also found that acyl-transfer between O- and N-atom on products occurred in the presence of DMAP.