Stereoselective syntheses of (E)- and (Z)-2,3-dihydro-3-(1,2,4-triazolyl)-4H-1-benzopyran-4-one oxime ethers

A synthesis of (E)-and (Z)-2,3-diliydro-3-(1H-1,2,4-triazol-1-yl)-4H-1-benz opyran4-one oxime ethers [(E)- and (Z)-13] and (Z)-2,3-diliydro-3-(4H-1,2,4 -triazol-4-yl)-4H-1-benzopyran-4-one oxime ethers [(Z)-17] are described. R ing closure of 2-(1,2,4-triazolyl)-2'-hydroxyacetophenones (5 or 6) followe d by reaction with HONH2.HCl 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-broino-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 front the reaction of 2,3-diliydr o-3-(1,2,4-triazolyl)-4H-1-benzopyran-4-ones (2 or 14) with O-(aryl-methyl) hydroxylamine hydrochloride (19).