Gold(I)-Catalyzed Synthesis of Optically Active 1,4-Oxazepan-7-ones
摘要:
Optically active seven-membered lactones, dimethyleneoxazepanones, were readily prepared in good yields from chiral beta-(N-propargylic)-amino-alpha-methylene carboxylic add tert-butyl esters in the presence of catalytic amounts of Ph3PAuCl and Cu(OTf)(2) A smooth 7-exo-dig cyclization was observed.
Bicyclodihydrosiloles were readily prepared from opticallyactive enyne compounds by a radical cascade reaction triggered by tris(trimethylsilyl)silane ((Me3Si)3SiH). The reaction was initiated by the addition of a silyl radical to an alpha,beta-unsaturated ester, forming an alpha-carbonyl radical that underwent radical cyclization to a terminal alkyne unit. The resulting vinyl radical attacked the silicon atom in an
通过由三(三甲基甲硅烷基)硅烷((Me3Si)3SiH)引发的自由基级联反应,可以很容易地从光学活性烯炔化合物制备双环二氢硅醇。该反应通过将甲硅烷基加入 α,β-不饱和酯引发,形成 α-羰基自由基,该自由基环化成末端炔单元。所得乙烯基自由基以 SHi 方式攻击硅原子,得到二氢硅酮。该反应优先形成双环硅氧烷的反式异构体,选择性约为 7:3 至 9:1。
A Radical Cascade Cyclization To Prepare Dihydrothiophenes Induced by Thiyl Radicals as Sulfur Biradical Equivalents
Bicyclic dihydrothiophenes are readily prepared by a radical cascade cyclization reaction triggered by the addition of a thiyl radical under thermal or photoirradiation conditions. The translocated radical attacks the sulfur atom in the initial radical donor unit in an S(H)i manner. Sufficient stereoselectivity is achieved when a large excess of disulfide is used for the reaction under photoirradiation conditions. The reaction in the absence of solvents provides vinylsulfides instead of dihydrothiophenes. Thus, the sulfur atom in the thiyl radical serves as a sulfur biradical synthetic equivalent.