Application of elementoorganic compounds of 15th and 16th Groups in organic synthesis. 100. Reactions of carbonyl compounds with [(trimethylsilyl)propargyl]diisobutyltelluronium bromide mediated by different strong bases: highly regioselective synthesis of (trimethylsilyl)propargyl alcohols and highly stereoselective synthesis of cis-(trimethylsilyl)alkynyl epoxides
摘要:
[(Trimethylsilyl)propargyl)]diisobutyltelluronium bromide (1), after being treated with alkyl- or aryllithium reagent, undergoes a lithium-tellurium exchange reaction via an unstable transient tetraorganyltellurium intermediate, and the in situ generated lithium species reacts with carbonyl compounds to give (trimethylsilyl)propargyl alcohols 2 in high yields with high regioselectivity. However, when the telluronium salt 1 was treated with nonnucleophilic bases such as LDA or lithium 2,2,6,6-tetramethylpiperidide, the moderately stabilized silylated telluronium ylide formed. The silylated telluronium ylide reacted with carbonyl compounds to afford (trimethylsilyl) alkynyl epoxides 11 in good to excellent yields with high cis stereoselectivity.
Enantioselective epoxidation of conjugated dienes and enynes. Trans-epoxides from cis-olefins
作者:Nam Ho Lee、Eric N. Jacobsen
DOI:10.1016/0040-4039(91)80212-o
日期:1991.11
Asymmetric epoxidation of conjugated dienes and enynes catalyzed by (salen)Mn(III) complex 1 takes place with high chemoselectivity to afford monoepoxides exclusively. Reactions of cis-enynes proceed with very high levels of asymmetric induction, with trans-alkynyl epoxides as the major products.
Facile and highly stereoselective synthesis of cis-trimethylsilylethynyl epoxides via a silylated telluronium ylide
作者:Zhang-Lin Zhou、Yao-Zeng Huang、Li-Lan Shi
DOI:10.1039/c39920000986
日期:——
Diisobutyltelluronium trimethylsilylpropynyl ylide, generated from 3-trimethylsilylprop-2-ynyldiisobutyltelluronium bromide with lithium 2,2,6,6-tetramethylpiperidide (LiTMP), reacts with carbonyl compounds to afford predominately cis-trimethylsilylethynyl epoxides in good to excellent yields.