共查询到20条相似文献,搜索用时 0 毫秒
1.
Pengcheng Lian Wenhao Long Jingjing Li Yonggao Zheng Prof. Dr. Xiaobing Wan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23809-23814
This work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl2 in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2-dichloride compounds using an inexpensive, low-molecular-weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C−Cl bonds in this synthetic process. 相似文献
2.
Jonathan Bock Sudip Guria Dr. Volker Wedek Prof. Dr. Ulrich Hennecke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(14):4517-4530
The dihalogenation of alkenes is one of the classic reactions in organic chemistry and a prime example of an electrophilic addition reaction. The often observed anti-selectivity in this addition reaction can be explained by the formation of a haliranium-ion intermediate. Although dihalogenations have been studied for more than a century, the development of reagent-controlled, enantioselective dihalogenation has proved to be very difficult. Only recently, significant progress has been achieved. In this review, an overview on current method development in enantioselective dihalogenation is provided and mechanistic aspects that render this transformation challenging are discussed. 相似文献
3.
4.
Michael T. Bovino Timothy W. Liwosz Nicole E. Kendel Dr. Yan Miller Dr. Nina Tyminska Prof. Eva Zurek Prof. Sherry R. Chemler 《Angewandte Chemie (International ed. in English)》2014,53(25):6383-6387
Chiral saturated oxygen heterocycles are important components of bioactive compounds. Cyclization of alcohols onto pendant alkenes is a direct route to their synthesis, but few catalytic enantioselective methods enabling cyclization onto unactivated alkenes exist. Herein reported is a highly efficient copper‐catalyzed cyclization of γ‐unsaturated pentenols which terminates in C? C bond formation, a net alkene carboetherification. Both intra‐ and intermolecular C? C bond formations are demonstrated, thus yielding functionalized chiral tetrahydrofurans as well as fused‐ring and bridged‐ring oxabicyclic products. Transition‐state calculations support a cis‐oxycupration stereochemistry‐determining step. 相似文献
5.
Dr. Michael Wilking Dr. Constantin G. Daniliuc Prof. Dr. Ulrich Hennecke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(51):18601-18607
The cinchona alkaloid dimer (DHQD)2PHAL has been shown to be a broadly applicable catalyst for asymmetric halogenations. However, this catalyst does not have to be dimeric and a class of monomeric quinidine and quinine‐derived catalysts was prepared, often showing superior selectivity in bromolactonisations of terminal alkynoic acids. Mechanistic investigations show that these organocatalysts act as host molecules that can bind carboxylic acid‐based substrates as guests with substantial binding constants. Based on these findings, it is proposed that this class of catalysts is bifunctional in nature activating the halogenating agent as well as the nucleophile in electrophilic halogenation reactions. 相似文献
6.
Organocatalytic Enantioselective Higher‐Order Cycloadditions of In Situ Generated Amino Isobenzofulvenes 下载免费PDF全文
Dr. Bjarke S. Donslund Dr. Alicia Monleón Dr. Teresa A. Palazzo Mette Louise Christensen Anne Dahlgaard Dr. Jeremy D. Erickson Prof. Karl Anker Jørgensen 《Angewandte Chemie (International ed. in English)》2018,57(5):1246-1250
The [8+2] cycloaddition of indene‐2‐carbaldehydes and nitro olefins is described to provide benzonorbornene scaffolds in a highly peri‐, diastereo‐, and enantioselective fashion in the presence of a C2‐symmetric aminocatalyst. This reaction, which proceeds through a transient semi‐aromatic amino isobenzofulvene, represents the first example of catalytic formation and transformation of these species. Quantum chemical calculations suggest a kinetically controlled stepwise mechanism where the stereochemistry is determined in the first bond‐forming event. Beyond the useful [8+2] cycloadducts, [10+4] cycloadducts have been identified in silico as potential off‐pathway intermediates. 相似文献
7.
Favoring Trienamine Activation through Unconjugated Dienals: Organocatalytic Enantioselective Remote Functionalization of Alkenes 下载免费PDF全文
Liher Prieto Dr. Garazi Talavera Dr. Uxue Uria Prof. Efraim Reyes Prof. Jose L. Vicario Prof. Luisa Carrillo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2145-2148
Unconjugated 2,5‐dienals are more reactive substrates than the corresponding fully conjugated α,β,γ,δ‐unsaturated aldehydes towards organocatalytic activation through trienamine intermediates. This difference in reactivity has been demonstrated in the Diels–Alder reaction with nitroalkenes, a reaction that proceeds with clean β,ε‐selectivity to afford the final products in high yields and stereoselectivities, the related polyconjugated 2,4‐dienals being completely unreactive. 相似文献
8.
9.
10.
11.
Dr. Xingguang Li Prof. Jianwei Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17197-17202
An organocatalytic enantioconvergent synthesis of chiral tetrasubstituted allenes is disclosed. With suitable chiral phosphoric acid catalysts, a range of racemic indole-substituted propargylic alcohols reacted with nucleophiles to provide efficient access to a series of enantioenriched allenes with high enantioselectivities. Control experiments suggested a mechanism involving remotely controlled asymmetric 1,8-addition of the in situ generated indole imine methide via a bifunctional transition state. 相似文献
12.
13.
14.
Dr. Pushpak Mizar Alessandra Burrelli Erika Günther Martin Söftje Prof. Dr. Umar Farooq Prof. Dr. Thomas Wirth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13113-13116
A new chiral thiohydantoin catalyst is used for the stereoselective iodoamination of alkenes. N‐iodosuccinimide as the source of the electrophilic iodine is activated by catalytic amounts of different additives which also influence the regioselectivity of some cyclizations. 相似文献
15.
An organocatalytic enantioconvergent synthesis of chiral tetrasubstituted allenes is disclosed. With suitable chiral phosphoric acid catalysts, a range of racemic indole‐substituted propargylic alcohols reacted with nucleophiles to provide efficient access to a series of enantioenriched allenes with high enantioselectivities. Control experiments suggested a mechanism involving remotely controlled asymmetric 1,8‐addition of the in situ generated indole imine methide via a bifunctional transition state. 相似文献
16.
有机小分子催化的不对称合成反应是目前研究最为活跃的领域之一. 不对称Strecker反应是合成光学活性α-氨基酸衍生物的有效手段. 目前报道的催化不对称Strecker反应的有机催化剂主要有手性胍类、手性(硫)脲衍生物、氮-氧偶极化合物、手性Brønsted酸等, 取得了良好的催化活性和对映选择性. 对各类有机小分子催化剂在有机催化不对称Strecker反应中的应用研究进展, 以及催化剂结构与反应条件对催化活性和不对称诱导作用的影响进行了简要评述. 相似文献
17.
Organocatalytic Enantioselective Decarboxylative Reaction of Malonic Acid Half Thioesters with Cyclic N‐Sulfonyl Ketimines by Using N‐Heteroarenesulfonyl Cinchona Alkaloid Amides 下载免费PDF全文
Prof.Dr. Shuichi Nakamura Masahide Sano Ayaka Toda Dr. Daisuke Nakane Prof.Dr. Hideki Masuda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3929-3932
The organocatalytic enantioselective decarboxylative Mannich reaction of malonic acid half thioesters (MAHTs) with cyclic N‐sulfonyl ketimines by using N‐heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. The reaction proceeds through a nucleophilic addition of the MAHTs to the ketimines prior to decarboxylation. 相似文献
18.
Dr. Ilona Behrends Susanne Bähr Prof. Dr. Constantin Czekelius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17177-17181
The activation of perfluoroalkyl iodides by the frustrated Lewis pair tris(pentafluorophenyl)borane and tri‐tert‐butylphosphine is described. By abstraction of both a fluorine and an iodine atom, an iodophosphonium fluoroborate salt is formed. In the presence of alkenes the corresponding iodoperfluoroalkylation products are generated regioselectively. First mechanistic investigations support a radical mechanism. 相似文献
19.
The direct three-component asymmetric Mannich reactions of hydroxyacetone with anilines and aromatic aldehydes in the presence of (2S,5S)-5-(methoxycarbonyl)pyrrolidine-2-carboxylic acid afforded syn-1,2-amino alcohols in good-to-excellent yields (55~91%) and up to 98% ee. 相似文献