Control of Regioselectivity in Pd(0)-Catalyzed Coupling−Cyclization Reaction of 2-(2‘,3‘-Allenyl)malonates with Organic Halides
作者:Shengming Ma、Ning Jiao、Shimin Zhao、Hairong Hou
DOI:10.1021/jo0108616
日期:2002.5.1
in the Pd(0)-catalyzed coupling-cyclization of 2-(2',3'-allenyl)malonates with organichalides is determined by the steric and electronic effects of both substrates. By deliberate control of the reaction conditions, the regioselectivity of this reaction can be tuned. With conditions A and B, the reaction afforded vinylic cyclopropane derivatives, while with conditions C and D, the reaction afforded
to substituted 3‐keto pyridines or 4‐picolines in very good yields. This pathway is in contrast to their known cyclization in the presence of Au(I) or Au(III) catalysts which provides 1,4‐oxazepines, instead. The enaminones are formed in situ upon mixing a conjugated allenone or allenyl ester with the alkynylamine, thus the pyridine‐forming transformation is typically a onepot process.
TiO 2上的可回收负载型Au纳米颗粒催化N-炔丙基或N-同炔丙基β-烯胺酮的环化,然后进行脱氢(芳构化),从而以非常好的收率产生取代的3-酮吡啶或4-甲基吡啶。该途径与已知在Au(I)或Au(III)催化剂存在下环化的相反,后者提供1,4-氧杂氮杂pine。烯胺酮是在将共轭的Allenone或Allenyl酯与炔基胺混合后原位形成的,因此形成吡啶的转化通常是一锅法。
Rhodium-Catalyzed Highly Enantio- and Diastereoselective Alkenylation of β,γ-Unsaturated Butenolides via Dynamic Kinetic Resolution
作者:Xiaosa Lu、Jie Zhu、Yinhua Huang
DOI:10.1021/acs.orglett.2c03551
日期:2022.12.9
diene ligand, (S,S)-Ph-bod, enables the facile synthesis of chiral butyrolactones in high yields with extremely high enantioselectivities (>99% ee in all cases) and high diastereoselectivities (up to >20:1 dr). The key process of the reaction involves the isomerization of β,γ-unsaturated butenolides to racemic α,β-unsaturated butenolides and the subsequent dynamic kinetic resolution through ligand-controlled
报道了一种铑催化的 β,γ-不饱和丁烯酸内酯的高度对映和非对映选择性烯基化反应。使用手性二烯配体 ( S , S )-Ph-bod,能够以高产率轻松合成手性丁内酯,具有极高的对映选择性(在所有情况下 >99% ee)和高非对映选择性(高达 >20: 1 博士)。反应的关键过程包括 β,γ-不饱和丁烯酸内酯异构化为外消旋 α,β-不饱和丁烯酸内酯,以及随后通过配体控制的动态动力学拆分,通过 1,4 原位生成的烯基铑物质进行对映选择性烯基化- 铑迁移。
Carboxylate Catalyzed Isomerization of β,γ‐Unsaturated
<i>N</i>
‐Acetylcysteamine Thioesters**
作者:Saara Riuttamäki、Gergely Laczkó、Ádám Madarász、Tamás Földes、Imre Pápai、Anton Bannykh、Petri M. Pihko
DOI:10.1002/chem.202201030
日期:2022.8.10
The power of carboxylates: Simple carboxylate salts can rival strong amidine bases, such as DBU, in their catalytic power to isomerize β,γ-unsaturated thioesters to corresponding conjugated α,β-unsaturated thioesters. The mechanism involves a rate-determining protonation step!
Efficient Synthesis of 4-(2‘-Alkenyl)-2,5-dihydrofurans and 5,6-Dihydro-2<i>H</i>-pyrans via the Pd-Catalyzed Cyclizative Coupling Reaction of 2,3- or 3,4-Allenols with Allylic Halides
作者:Shengming Ma、Wenzhong Gao
DOI:10.1021/jo0163997
日期:2002.8.1
In the absence of a base, palladium(II) catalysts, such as PdCl2, PdCl2(CH3CN)(2), Pd(OAc)(2), and [(pi-C3H5)PdCl](2), can catalyze the cyclizative coupling reaction of 2,3- or 3,4-allenols with allylic halides in DMA at room temperature to provide 2,5-dihydrofurans and 5,6-dihydro-2H-pyrans, respectively, in moderate to good yields. Under similar reaction conditions, nonsubstituted 2,3-allenol 1s affords bimolecular cyclizative coupling product 5s as the major product. The scope of the reaction and its mechanism have been studied briefly. On the basis of the experimental results, the transformation was believed to proceed via a divalent palladium-catalyzed pathway.