Unusual Regioselection in the Mitsunobu Reactions of syn-2,3-Dihydroxy Esters: Synthesis of Statine and Its Diastereomer
摘要:
Mitsunobu reactions of syn-2,3-dihydroxy esters exhibit a complete regioselection for the beta-hydroxyl group. Benzoylation, azidation, and tosylation have been performed under these conditions. beta-Functionalizations of syn-2,3-dihydroxy esters are uncommon, and the Mitsunobu reactions are complementary to other diol chemistries in the regioselection. In addition, the configurational inversion accompanying the Mitsunobu protocol offers a means for diastereochemical diversity, as exemplified by a synthesis of statine and its anti diastereomer. These findings will further expand the synthetic utilities of the Sharpless AD process.
Osmium tetroxide in poly(ethylene glycol) (PEG): a recyclable reaction medium for rapid asymmetric dihydroxylation under Sharpless conditionsDedicated to Prof. Goverdhan Mehta on his 60th birthday.Electronic supplementary information (ESI) available: experimental details. See http://www.rsc.org/suppdata/cc/b3/b305154b/
Manganese catalyzed cis-dihydroxylation of electron deficient alkenes with H2O2
作者:Pattama Saisaha、Dirk Pijper、Ruben P. van Summeren、Rob Hoen、Christian Smit、Johannes W. de Boer、Ronald Hage、Paul L. Alsters、Ben L. Feringa、Wesley R. Browne
DOI:10.1039/c0ob00102c
日期:——
A practical method for the multigram scale selective cis-dihydroxylation of electron deficient alkenes such as diethyl fumarate and N-alkyl and N-aryl-maleimides using H2O2 is described. High turnovers (>1000) can be achieved with this efficient manganese based catalyst system, prepared in situ from a manganese salt, pyridine-2-carboxylic acid, a ketone and a base, under ambient conditions. Under optimized conditions, for diethyl fumarate at least 1000 turnovers could be achieved with only 1.5 equiv. of H2O2 with d/l-diethyl tartrate (cis-diol product) as the sole product. For electron rich alkenes, such as cis-cyclooctene, this catalyst provides for efficient epoxidation.
(OsO42−) core dendrimers was prepared by an ion-exchange technique through the mixing of K2OsO4 and a bis(quaternary ammonium bromide) core dendrimer, which consisted of poly(benzyl ether) dendron. By employing an osmate core dendrimer as a homogeneous catalyst, dihydroxylation reactions of olefins proceeded rapidly, and the dendritic osmium catalyst was recovered by reprecipitation and then reused. Furthermore
通过离子交换技术,通过混合K 2 OsO 4制备了一系列渗透酸(OsO 4 2-)核心树枝状大分子双(季铵溴化)核心树状聚合物,其由聚(苄基醚)树突组成。通过使用渗透性核树枝状聚合物作为均相催化剂,烯烃的二羟基化反应迅速进行,并且通过再沉淀回收树枝状催化剂,然后再使用。此外,观察到树枝状对催化剂的可循环性的影响。在不对称二羟基化反应的情况下,以高化学收率得到适当的对映体过量(ee)的相应的二醇。在这种情况下,不仅树状的catalyst催化剂,而且手性配体也可以通过再沉淀而回收,并且可以有效地重复使用多达五次。
Multifunctional catalyst useful in the synthesis of chiral vicinal diols and process for the preparation thereof
申请人:Council of Scientific and
Industrial Research
公开号:EP1346767A1
公开(公告)日:2003-09-24
The present invention relates to a multifunctional reusable catalyst and to a process for the preparation thereof on a single matrix of the support to perform multicomponent reaction in a single pot. The multifunctional catalysts of the invention are useful for the synthesis of chiral vicinal diols by tandem and / or simultaneous reactions involving Heck coupling, N-oxidation and AD reaction of olefins in presence of cinchona alkaloid compounds both as an native one and immobilized one in the said matrix support. This invention also relates to a process for preparing vicinal diols by asymmetric dihydroxylation of olefins in presence of cinchona alkaloid compounds employing reusable multifunctional catalysts as heterogeneous catalysts in place of soluble osmium catalysts.
本发明涉及一种多功能可重复使用的催化剂,以及一种在单一支撑基质上制备该催化剂的方法,用于在单一锅中执行多组分反应。本发明的多功能催化剂可用于在金鸡纳生物碱化合物的存在下,通过串联和/或同时反应合成手性邻二醇,涉及 Heck 偶联、N-氧化和烯烃的 AD 反应。该催化剂可以作为原生态和固定化的形式存在于所述支撑基质中。本发明还涉及一种通过在金鸡纳生物碱化合物的存在下,利用可重复使用的多功能催化剂作为异质催化剂来代替可溶性的钌催化剂,合成邻二醇的方法。
Process for preparing diltiazem using a heterogeneous trifunctional catalyst
申请人:COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
公开号:US20040127704A1
公开(公告)日:2004-07-01
The present invention comprises a simplified synthesis of (+)-diltiazem through IE-PdOsW wherein IE is ion-exchanger, catalyzed three-component coupling reaction and Fe
3+
-exchanged clay catalyzed ring opening of sulfite with 2-aminothiophenol followed by cyclization as key steps.
Catalytic asymmetric dihydroxylation of alkenes using silica gel supported cinchona alkaloid
作者:B.B. Lohray、E. Nandanan、Vidya Bhushan
DOI:10.1016/0957-4166(96)00367-9
日期:1996.10
Immobilization of 3,6-bis(9-O-dihydroquinyl)pyridazine and 3,6-bis(9-O-dihydroquinidyl) pyridazine on silica gel support has been reported, The use of immobilized auxiliary has lead to comparable rate with that of the homogeneous catalytic AD of alkenes, however with lower ee. Copyright (C) 1996 Elsevier Science Ltd