Glyoxylic acid diphenylhydrazone (2, Y = NPh
2
) and the
corresponding O-benzyloxime (2, Y = OBn) are easily esterified in
high yield by β-bromo alcohols, and the resulting esters undergo
radical cyclization to α-(2,2-diphenylhydrazino) or
α-(benzyloxyamino) lactones on treatment with tributyltin hydride;
the initial radical can be formed by homolysis of a carbonâselenium
bond as well as a carbonâbromine bond and, when applied to
appropriate alcohols, the esterificationâradical closure sequence
can also be used to make six- or seven-membered lactones.
乙醛酸二苯基腙(2,Y = NPh 2)和相应的 O-苄基
肟(2,Y = OBn)很容易被δ-
溴醇高产率地酯化,生成的酯在用氢化三
丁基锡处理时会发生自由基环化,生成δ-(2,2-二苯基腙)或δ-(苄氧基
氨基)内酯;
初始自由基可通过碳
硒键和碳
溴键的均裂作用形成,当应用于适当的
醇类时,酯化和自由基闭合顺序也可用于制造六元或七元内酯。