Gold-Catalyzed Formal [3 + 3] and [4 + 2] Cycloaddition Reactions of Nitrosobenzenes with Alkenylgold Carbenoids
作者:Vinayak Vishnu Pagar、Appaso Mahadev Jadhav、Rai-Shung Liu
DOI:10.1021/ja209980d
日期:2011.12.28
We report two new formal cycloaddition reactions between nitrosobenzenes and alkenylgold carbenoids. We obtained quinoline oxides 3 in satisfactory yields from the gold-catalyzed [3 + 3]-cycloadditions between nitrosobenzenes and alkenyldiazo esters 1. For propargyl esters 5, its resulting gold carbenes react with nitrosobenzene to give alkenylimine 8, followed by a [4 + 2]-cycloaddition with nitrosobenzene
Neighboring Carbonyl Group Assisted Oxyacetoxylation of Propargylic Carboxylates with Retention of Chirality under Metal Free Condition
作者:Tapas R. Pradhan、Debendra K. Mohapatra
DOI:10.1002/adsc.201900314
日期:2019.8.5
reaction proceeds through the intramolecular nucleophilic attack of the neighboring carbonyl group on an alkynyliodonium intermediate. The process is general with broad substrate scope and is amenable for application to a variety of propargyl carboxylates including those obtained from naturalproducts. Insight into the mechanistic pathway by isotopic labelling (using H2O18 and D2O) and controlled experiments
提出了保留手性的伯,仲和叔炔丙基羧酸的无金属氧乙酰氧基化方法。该反应通过烷基炔酮中间体上相邻羰基的分子内亲核攻击而进行。该方法是一般的,具有广泛的底物范围,并且适用于包括从天然产物获得的那些炔丙基羧酸酯。通过同位素标记(使用H 2 O 18和D 2 O)洞察机械途径,并确认了对照实验。
Transition metal-catalyzed pentannulation of propargyl acetates via styrylcarbene intermediates
作者:Yusuke Nakanishi、Koji Miki、Kouichi Ohe
DOI:10.1016/j.tet.2007.09.064
日期:2007.12
achieved by platinum or ruthenium catalysis via E-vinylcarbenoid intermediate. Considering the competitive reactions of pentannulation versus cyclopropanation, the equilibrium ratios of E and Z vinylcarbenoid intermediates from sec- and tert-propargyl esters are estimated at ca. 10:90 and 40:60, respectively. Two reaction pathways, Nazarov-type cyclization and/or metallacycle from styrylcarbenoid species
Heterogeneous Acid-Catalyzed Racemization of Tertiary Alcohols
作者:Tamás Görbe、Richard Lihammar、Jan-E. Bäckvall
DOI:10.1002/chem.201704691
日期:2018.1.2
synthesis but only few methods are known for their enantioselective preparation. Chiral resolution is one of these approaches that leaves one enantiomer (50 % of the material) unaffected. An attractive method to increase the efficiency of those resolutions is to racemize the unaffected enantiomer. In the present work, we have developed a practical racemization protocol for tertiary alcohols. Five different