The [2,3]-Wittig rearrangements of lithioalkyl allyl ethers exhibit different cis,trans-selectivities than [2,3] shifts in their lithiomethyl analogues
摘要:
The reductive lithiation of O,S-acetals 9a-d initiated [2,3]-Wittig rearrangements whose cis,trans-selectivity depended on whether lithiomethyl (--> cis) or lithioalkyl allyl ethers reacted (--> trans). It is suggested that these rearrangements proceed via mixtures of the configurationally stable lithioether intermediates syn-13 and anti-13 and transition states 17(endo,exo) and 17(endo,endo), respectively.
Regioselective Ni-Catalyzed Carboxylation of Allylic and Propargylic Alcohols with Carbon Dioxide
作者:Yue-Gang Chen、Bin Shuai、Cong Ma、Xiu-Jie Zhang、Ping Fang、Tian-Sheng Mei
DOI:10.1021/acs.orglett.7b01208
日期:2017.6.2
efficient Ni-catalyzed reductive carboxylation of allylic alcohols with CO2 has been successfully developed, providing linear β,γ-unsaturated carboxylic acids as the sole regioisomer with generally high E/Z stereoselectivity. In addition, the carboxylic acids can be generated from propargylicalcohols via hydrogenation to give allylic alcohol intermediates, followed by carboxylation. A preliminary mechanistic
Stereospecific Intramolecular C–H Amination of 1-Aza-2-azoniaallene Salts
作者:Daniel A. Bercovici、Matthias Brewer
DOI:10.1021/ja303054c
日期:2012.6.20
participate in intramolecularC-H amination reactions to provide pyrazoline products in good to excellent yield. This intramolecular amination occurs readily at both benzylic and tertiary aliphatic positions and proceeds at an enantioenriched chiral center without loss of enantiomeric excess. A competition reaction shows that insertion occurs more readily at an electron-rich benzylic position than an
Ligand-Controlled Regiodivergent Silylation of Allylic Alcohols by Ni/Cu Catalysis for the Synthesis of Functionalized Allylsilanes
作者:Yi Gan、Wei Xu、Yuanhong Liu
DOI:10.1021/acs.orglett.9b03822
日期:2019.12.6
Ni/Cu-catalyzed regiodivergent synthesis of allylsilanes directly from allylicalcohols through modulating the steric and electronic properties of the ligands on the nickel catalyst has been developed. Good yields and excellent selectivity were obtained regardless of whether linear or α-branched allylicalcohols were utilized. Mechanistic studies indicate that an allyloxyboronate species is formed during the
[2,3]-Thia-Wittig rearrangements with A marked starting material dependence of stereoselectivity
作者:Holger von der Emde、Reinhard Brückner
DOI:10.1016/s0040-4039(00)60177-6
日期:1992.11
[2,3]-Thia-Wittig rearrangements were initiated (a) by Sn,Li exchange of stannyl sulfides type 5 (X = S) and (b) by reductive lithiation of S,S-acetals type 6 (X = S). Homoallyl thiols were obtained in yields between 49 and 96%. E:Z selectivities of these rearrangements were low while syn:anti selectivities could be high. Extent and sense of both kinds of stereocontrol depended on whether procedure
Direct C–C Bond Formation of Allylic Alcohols with CO<sub>2</sub> toward Carboxylic Acids by Photoredox/Nickel Dual Catalysis
作者:Zhengning Fan、Shenhao Chen、Song Zou、Chanjuan Xi
DOI:10.1021/acscatal.2c00418
日期:2022.3.4
Carboxylation of allylic alcohols with carbondioxide is accomplished by photoredox/nickel dual catalysis, generating linear acids exclusively with good Z/E stereoselectivity. Hantzsch ester is employed as the reductant instead of stoichiometric metallic reductants, and the reaction can be conducted under room temperature with a blue LED light source. Mechanisticstudies reveal that the presence of
烯丙醇与二氧化碳的羧基化是通过光氧化还原/镍双重催化完成的,仅生成具有良好Z/E立体选择性的线性酸。采用 Hantzsch 酯代替化学计量的金属还原剂作为还原剂,反应可以在室温下用蓝色 LED 光源进行。机理研究表明,该催化体系中水的存在对反应的成功至关重要,并且反应更有可能在原位形成的烯丙基碳酸氢盐的氧化加成中进行。