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.
Highly Enantioselective Organocatalytic Oxidative Kinetic Resolution of Secondary Alcohols Using Chiral Alkoxyamines as Precatalysts: Catalyst Structure, Active Species, and Substrate Scope
The development and characterization of enantioselective organocatalyticoxidative kinetic resolution (OKR) of racemic secondaryalcoholsusing chiral alkoxyamines as precatalysts are described. A number of chiral alkoxyamines have been synthesized, and their structure-enantioselectivity correlation study in OKR has led us to identify a promising precatalyst, namely, 7-benzyl-3-n-butyl-4-oxa-5-azahomoadamantane
Osmium-catalyzed dihydroxylation of alkenes by H2O2 in room temperature ionic liquid co-catalyzed by VO(acac)2 or MeReO3
作者:Mikael Johansson、Auri A. Lindén、Jan-E. Bäckvall
DOI:10.1016/j.jorganchem.2005.04.033
日期:2005.8
immobilize a bimetallic catalytic system for H2O2-based dihydroxylation of alkenes. Osmium tetroxide was used as the substrate-selective catalyst with either VO(acac)2 or MeReO3 as co-catalyst. The latter serve as an electron transfer mediator (ETM) and activates H2O2. For an increased efficiency N-methylmorpholine is required as an additional ETM in most cases. A range of alkenes were dihydroxylated using
室温离子液体[bmim] PF 6用于固定双金属催化体系,用于烯烃的基于H 2 O 2的二羟基化。四氧化s用作底物选择催化剂,VO(acac)2或MeReO 3用作助催化剂。后者用作电子转移介体(ETM),并激活H 2 O 2。为了提高效率,在大多数情况下,需要N-甲基吗啉作为额外的ETM。使用这种坚固的双金属体系,一系列烯烃被二羟基化,结果表明,对于某些烯烃,催化体系可以循环使用多达五次。
Mechanistically Driven Development of an Iron Catalyst for Selective <i>Syn</i>-Dihydroxylation of Alkenes with Aqueous Hydrogen Peroxide
作者:Margarida Borrell、Miquel Costas
DOI:10.1021/jacs.7b07909
日期:2017.9.13
to be resolved in the design of iron catalysts for olefin syn-dihydroxylation with potential utility in organic synthesis. Toward this end, in this work a novel catalyst bearing a sterically encumbered tetradentate ligand based in the tpa (tpa = tris(2-methylpyridyl)amine) scaffold, [FeII(CF3SO3)2(5-tips3tpa)], 1 has been designed. The steric demand of the ligand was envisioned as a key element to support
polymer-supported osmium catalyst has been developed. The catalyst was prepared from commercially available polysulfone, based on a microencapsulation technique and was employed in the asymmetric dihydroxylation of various olefinsusing (DHQD)2PHAL as the chiral ligand and NMO as the co-oxidant in H2O–acetone–CH3CN (1:1:1). The catalyst was recovered by simple filtration and was reused to obtain excellent yields with
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.