Stereoselective Syntheses of (E)-and (Z)-2,3-Dihydro-3(1,2,4-Triazolyl)-4H-1-Benzopyran-4-one oxime Ethers

摘要

A synthesis of (E)-and (Z)-2,3-dihydro-3-(1H-1,2,4-triazol-1-yl)-4H-1-benzopyran-4-one oxime ethers [(E)-and (Z)-13] and (Z)-2,3-dihydro-3(4H-1,2,4-triazol-4-yl)-4H-1-benzopyran-4-one oxime ethers [(Z)-17] are described. Ring closure of 2-(1,2,4-triazolyl)-2'-hydroxy-acetophenones (5 or 6) followed by reaction with HONH_2HCl gave the corresponding (Z)-oximes [(Z)-11 or (Z)_16]. O-Alkylation of (Z)-oximes afforded (Z)-oxime ethers [(Z)-13 or (Z)-17]. Reaction of (Z)-3-bromo-2,3-dihydro-4H-1-benzopyran-4-one oxime (18) with 1,2,4-triazole afforded (E)-oxime [(E)-11]. O-Alkylation of (E)-oxime gave the desired (E)-oxime ethers [(E)-13]. In addition, (Z)-oxime ethers [(Z)-13 or (Z)-17] could also be obtained from the rection of 2,3-dihydro-3-(1,2,4-triazolyl)-4H-1-benzopyran-4-ones (2 or 14) with O-(aryl-methyl)hydroxylamine hydrochloride (19).