Enantioselective Copper-Catalyzed Reductive Michael Cyclizations
摘要:
In the presence of siloxanes as stoichiometric reductants, chiral copper-bisphosphine complexes catalyze highly enantioselective reductive Michael cyclizations of substrates containing two alpha,beta-unsaturated carbonyl moieties. The diastereochemical outcome of these reactions is dependent upon whether biaryl- or ferrocene-based chiral bisphosphines are employed.
Chemically Induced Anion Radical Cycloadditions: Intramolecular Cyclobutanation of Bis(enones) via Homogeneous Electron Transfer
作者:Jingkui Yang、Greg A. N. Felton、Nathan L. Bauld、Michael J. Krische
DOI:10.1021/ja030543j
日期:2004.2.1
The first examples of anionradical cycloaddition induced by homogeneous electrontransfer from chemical agents are described. Specifically, upon exposure to chrysene anionradical, bis(enone) substrates are found to engage in stereoselective intramolecular [2 + 2] cycloaddition. These studies, along with the corresponding electrochemically initiated reactions, provide insight into this fundamentally
text] Treatment of formyl alpha,beta-enones with a TiCl(4)-R(4)NX combination induces an intramolecular aldolcyclization to furnish 2-acyl-3-halocyclohexanol with three controlled consecutive stereogenic centers. The reaction of bis-alpha,beta-enones with the combination provides cyclic diketones with high stereoselectivity via an intramolecular Michael addition reaction.
Stereoselective formation of carbocycles was carried out through [RhCl(cod)]2-catalyzed reactions of alkenylzirconocene chloride to ω-carbonyl-α,β-ene carbonyls (ketone, ester, and amide) or to bis-enone derivatives. The Rh(I)-catalyzed reaction of alkenylzirconocene chloride with ω-carbonyl-α,β-enoyl amide, which is derived from Oppolzer’s sultam, showed high diastereoselectivity to yield an carbocycle (95%
Acylzirconocene chloride: Formation of carbocycles by palladium-catalyzed cascade reaction
作者:Yuji Hanzawa、Yusuke Oka、Masaya Yabe
DOI:10.1016/j.jorganchem.2007.04.033
日期:2007.10
function in an initial step, (ii) an acyl group transfer from the acylzirconocenecomplex to the Pd(II)-intermediate (transmetalation), (iii) the reductive elimination of Pd(0)-metal, and (iv) an intramolecular addition of metal enolate to ω-carbonyl group. On the other hand, the reaction of bis-enones with acylzirconocenechloride under the identical condition afforded reductive cyclization product
在10 mol%Pd(OAc)2催化的条件下,酰基锆茂氯化物配合物作为酰基供体与ω-羰基α,β-烯酮或与双烯酮反应生成碳环化合物,并且通过添加a Me 2的化学计量锌 由ω-羰基α,β-烯酮形成碳环被认为是一系列反应的结果。(i)在初始步骤中通过电子从Pd(0)催化剂转移到α,β-烯酮官能团形成Pd(II)中间体,(ii)酰基从茂锆茂配合物转移到Pd(II)中间体上Pd(II)-中间体(金属转移),(iii)Pd(0)-金属的还原消除,和(iv)金属烯醇化物到ω-羰基的分子内加成。另一方面,在相同条件下双烯与氯化烯锆茂反应可得到还原环化产物双环[3.3.0]辛烷衍生物,其中未掺入酰基锆茂复合物的酰基。
Asymmetric Intramolecular Rauhut–Currier Reaction and Its Desymmetric Version via Double Thiol/Phase-Transfer Catalysis
intramolecular Rauhut–Currier reaction of linear bis(enones) has been achieved via double activation catalysis of thiols and phase transfer substances, furnishing both enantioenriched cyclohexene and cyclopentene derivatives (up to 95% ee). Furthermore, the desymmetric version of prochiral substrates was developed under similar catalysis, producing the frameworks bearing an additional tertiary or even quaternary