通过采用氘标记的底物,三氟甲磺酸催化的分子内外型加成的X H(d)(X = N,O)磺酰胺,醇的键,或跨越挂件环己烯的CC键羧酸通过1 H 和2 H NMR 光谱和质谱分析确定,在每种情况下,都发生了完全形成 (≥90%) 的抗加成产物,而没有氘的损失或扰乱。的三氟甲磺酸,酸催化的分子内加氢胺化的动力学分析ñ - (2- ç yclohex -2'-烯基- 2,2-二苯基乙基) - p -toluenesulfonamide(1一) 建立了二阶速率定律:rate= k 2 [HOTf][ 1a ] 和激活参数 Δ H ≠ =(9.7±0.5) kcal mol -1和 Δ S ≠ =(-35±5) cal K - 1 摩尔-1。在1 a的 C2' 位置氘化后观察到k D / k H =(1.15±0.03)的逆 α-二级动力学同位素效应,这与催化加氢胺化的最高能量过渡态中部分 C
Intramolecular Hydroalkoxylation of Unactivated Alkenes Using Silane–Iodine Catalytic System
摘要:
A novel catalytic system using I-2 and PhSiH3 for the intramolecular hydroalkoxylation of unactivated alkenes is described. NMR study indicated that in situ generated PhSiH2I is a possible active catalytic species. This catalytic system allows an efficient intramolecular hydroalkoxylation of phenyl-, trialkyl-, and 1,1-dialkyl-substituted alkenes as well as a variety of unactivated monoalkyl- and 1,2-dialkyl-substituted alkenes at room temperature. Mechanistic consideration based on significant experimental observations is also discussed.
catalyzed intramolecular hydroalkoxylation reaction is presented, as a transition metal free, inexpensive, and very mild process for the highly atom economic formation of cyclic ethers from γ,δ-unsaturated alcohols. In contrast to most of the previously reported procedures, roomtemperature conditions are fully sufficient in most cases for a high yielding cycloisomerization in the presence of a combination
Platinum-Catalyzed Intramolecular Hydroalkoxylation of γ- and δ-Hydroxy Olefins to Form Cyclic Ethers
作者:Hua Qian、Xiaoqing Han、Ross A. Widenhoefer
DOI:10.1021/ja0477773
日期:2004.8.1
4-diphenyltetrahydrofuran in 78% yield. The platinum-catalyzed hydroalkoxylation of γ-hydroxy olefins tolerated substitution at the α, β, and γ-carbon atoms and at the internal and cis and trans terminal olefinic positions. Platinum-catalyzed hydroalkoxylation tolerated a number of functional groups including pivaloate and acetate esters, amides, silyl and benzyl ethers, and pendant hydroxyl and olefinic groups
Abstract Cyclization of enantiopure (S/R)-1 with halogen-reagent-constructed enantiopure octahydrobenzofuran core structure with contiguous three stereogenic centers of both enantiomers (SRR and RSS). The absolute configurations of all compounds have been established from x-ray analysis of the single crystal of (3aS,7aR,7R)-3. The chiral initiation in diastereoselective mode of 5-exo ringclosure across
Non-superimposable mirror image crystals of both enantiomers (S/R) of cyclic gamma-alkenyl alcohol (2) have been recognized and remarkably identified by the naked eye. More interestingly, both crystals are an outcome of most astonishingly H-bond and intermolecular sigma/pi-pi interactions. They accounted for the relatively rare and less predictable spontaneous resolution with optical purity >99% ee from the racemic mixture. The chiral discrimination mechanism of this spontaneous resolution has also been proposed. (c) 2013 Fu-Xue Chen. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.