Synthesis of .gamma.- and .delta.-lactones by free-radical annelation of Se-phenyl selenocarbonates
摘要:
A general method for the synthesis of gamma- and delta-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu3SnH, onto carbon-carbon multiple bonds is described. This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction. Monocyclic, fused bicyclic, and spirocyclic lactones are formed in good to excellent yield. Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu3SnH affords the corresponding 3-butenyl lactones.
Synthesis of α-alkylidene-γ-lactones by intramolecular addition of alkoxycarbonyl free-radicals to acetylenes
作者:Mario D. Bachi、Eric Bosch
DOI:10.1016/s0040-4039(00)84062-9
日期:1986.1
α-Alkylidene-γ-lactones are obtained by treatment of chloroformate and selenocarbonate derivatives of homopropargylic alcohols with tri-n-butylstannane.
Formal Alkyne Aza-Prins Cyclization: Gold(I)-Catalyzed Cycloisomerization of Mixed N,O-Acetals Generated from Homopropargylic Amines to Highly Substituted Piperidines
作者:Cheoljae Kim、Hyo Jin Bae、Ji Hyung Lee、Wook Jeong、Haejin Kim、Vasu Sampath、Young Ho Rhee
DOI:10.1021/ja906744r
日期:2009.10.21
cycloisomerization to access highly substituted piperidines has been developed. By combining a conceptually new way of generating iminium ions using cationic gold(I) complexes and an efficient cyclization reaction that can minimize a potentially competing aza-Cope rearrangement, the proposed reaction successfully circumvents a long-standing problem in the classical aza-Prins reaction. Synthetic utility of the catalytic
Hydroalkylation of Alkynyl Ethers via a Gold(I)-Catalyzed 1,5-Hydride Shift/Cyclization Sequence
作者:Igor Dias Jurberg、Yann Odabachian、Fabien Gagosz
DOI:10.1021/ja9100134
日期:2010.3.17
A series of alkynyl ethers react with an electrophilic gold(I) catalyst to produce a range of structurally complex spiro or fused dihydrofurans and dihydropyrans via a 1,5-hydride shift/cyclization sequence. This hydroalkylation process, which is performed under practical experimental conditions, can be applied to terminal as well as ester-substituted alkynes. It allows the efficient conversion of
一系列炔基醚与亲电子金 (I) 催化剂反应,通过 1,5-氢化物转移/环化序列产生一系列结构复杂的螺或稠合二氢呋喃和二氢吡喃。这种在实际实验条件下进行的加氢烷基化过程可应用于末端和酯取代的炔烃。它允许通过将乙烯基金物质亲核加成到氧鎓中间体上,将二级或三级 sp(3) CH 键有效转化为新的 CC 键。形成新的五元或六元环的环异构化过程的立体选择性似乎取决于空间因素和炔烃取代模式。
Synthesis of Functionalized Cyclopentanes, Cyclohexanes and Cycloheptanes by a Silicon-Induced Domino Reaction
1,3-Functionalized cyclopentanes, -hexanes and -heptanes are obtained by addition of lithiated silyldithioacetals 7 to epoxyhomoallyl tosylates 4–6, The reaction involves a cascade of epoxide ring opening, of Brook 1,4-rearrangement and tosylate substitution. The method is particularly suitable for the preparation of cyclopentanes, whereas cyclohexanes and -heptanes are formed in yields only up to
The Au‐catalyzed reactions of O‐homopropaylic oximes afforded the 3‐alkenylated isoxazolines in good to high yields. The mechanistic studies suggest that the reaction proceeds through an exo‐cyclization followed by intermolecular methylene group transfer. In addition, oligomeric species of the starting material were observed in the reaction mixture by mass spectra, supporting our proposed mechanism