3,5-Disubstituted-1,2,4-oxadiazoles and 4,5-dihydro-3,5-disubstituted-1,2,4-oxadiazoles
作者:Harry L. Yale、E. R. Spitzmiller
DOI:10.1002/jhet.5570150825
日期:1978.12
procedure either failed or gave low yields with other aldehydes. A novel alternative method, the diborane reduction of 2, has been found to be a generally applicable procedure for preparing 5. The reduction is regioselective, i.e., only the 4,5-(C=N) linkage is reduced even when a large excess of diborane is present.
由单或二氯苯基取代的mid胺肟和(i)酰氯,(ii)异丙酸酐或(iii)制备一系列3,5-二取代-1,2,4-恶二唑(2)。 β-酮酯。尽管相同的酰胺肟与乙醛的环化反应产生了4,5-二氢-5-甲基取代的衍生物(5),但是这种环合方法要么失败,要么与其他醛的收率低下。已经发现一种新颖的替代方法,乙硼烷还原2,是制备5的普遍适用的程序。所述还原是区域选择性的,即,即使存在大量过量的乙硼烷,也仅还原4,5-(C = N)键。