One-pot reductive cleavage of exo-olefin to methylene with a mild ozonolysis-Clemmensen reduction sequence
摘要:
A one-pot exo-olefin reductive cleavage was for the first time developed. The reaction could proceed under a mild condition avoiding the use of hazardous and expensive reagents. Meanwhile, a TMSCl-mediated Clemmensen reduction in alcoholic solvent was also examined. (C) 2010 Elsevier Ltd. All rights reserved.
通过使盐酸与两种差向异构的3-羟基-3-甲基-5α-胆甾烷反应,制得3α-氯-3β-甲基-和3β-氯-3α-甲基-5α-胆甾烷。用四甲基-1-氯乙烯基胺作为氯化剂,可以获得更好的收率和更清洁的转化率。两种3-甲基-5α-胆甾醇与三苯基膦-四氯化碳或三氯化磷-吡啶的反应生成了3-甲基-5α-胆甾-2-烯,3-甲基-5α-胆甾-3-烯和3-亚甲基-5α-胆甾烷。通过用(二乙基氨基)三氟化硫处理两个3-甲基-5α-胆甾烷-3-醇,获得了两个差向异构的3-氟-3-甲基-5α-胆甾烷。3-卤代-3-甲基-5α-胆甾烷的构型由它们的13个决定C nmr光谱。两种3-卤代-3-甲基-5α-胆甾烷差向异构体的可用性使800-400 cm -1区域的红外光谱得到了明确的解释。
Controllable Isomerization of Alkenes by Dual Visible‐Light‐Cobalt Catalysis
作者:Qing‐Yuan Meng、Tobias E. Schirmer、Kousuke Katou、Burkhard König
DOI:10.1002/anie.201900849
日期:2019.4.16
We report herein that thermodynamic and kineticisomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction
Various carbon-carbon double bonds in olefins and α,β-unsaturatedketones were effectively reduced to the corresponding alkanes and saturated ketones, using ammoniumformate as a hydrogentransfer agent in the presence ofPd/C as catalyst in refluxing methanol.
以甲酸铵为氢转移剂,Pd/C为催化剂,甲醇回流。
Efficient and Stereoselective Nitration of Mono- and Disubstituted Olefins with AgNO<sub>2</sub> and TEMPO
common and versatile reagent. Its synthesis from olefin is generally limited by the formation of mixture of cis and trans compounds. Here we report that silver nitrite (AgNO2) along with TEMPO can promote the regio- and stereoselective nitration of a broad range of olefins. This work discloses a new and efficient approach wherein starting from olefin, nitroalkane radical formation and subsequent transformations
硝基烯烃是一种常见且用途广泛的试剂。它从烯烃合成通常受到顺式和反式化合物混合物的形成的限制。在这里,我们报告亚硝酸银 (AgNO2) 与 TEMPO 一起可以促进范围广泛的烯烃的区域和立体选择性硝化。这项工作公开了一种新的有效方法,其中从烯烃开始,硝基烷烃自由基形成和随后的转化以立体选择性方式导致所需的硝基烯烃。
Liquid crystals based on hypervalent sulfur fluorides
作者:Peer Kirsch、Jörg T. Binder、Enno Lork、Gerd-Volker Röschenthaler
DOI:10.1016/j.jfluchem.2005.11.015
日期:2006.5
New liquidcrystals with a pentafluorosulfanyl function as their polar terminal group were prepared and fully characterized. The synthetic key step was the triethyl borane-catalyzed addition of SF5Br to a suitable olefin precursor, followed by dehydrobromination. The most interesting characteristic of the new materials is their combination of high polarity (Δɛ) with very low birefringence (Δn), which
Synthesis and transformations of metallacycles 42. Cp2ZrCl2-Catalyzed cycloalumination of 3-methylidenespiro[cyclobutane-1,3′-(5′α)-cholestane] with Et3Al
作者:U. M. Dzhemilev、R. A. Tuktarova、I. I. Islamov、L. M. Khalilov、Z. A. Starikova、V. A. D’yakonov
DOI:10.1007/s11172-013-0027-z
日期:2013.1
A Cp2ZrCl2-catalyzed cycloalumination of 3-methylidenespiro[cyclobutane-1,3′-(5′α)-cholestane] with Et3Al gives 3-ethyl-3-aluminadispiro[cyclopentane-1,1′-cyclobutane-3′,3″-(5″α)-cholestane] in 84% yield.