119240-64-1Relevant articles and documents
Diamination of Olefins: Synthesis, Structures and Reactivity of Osmaimidazolidines
Muniz, Kilian,Iesato, Atsushi,Nieger, Martin
, p. 5581 - 5596 (2003)
The diamination of certain olefins bearing electron-withdrawing substituents proceeds with well-defined bisimido and trisimido complexes of osmium. The products are obtained as osmaimidazolidines which are of unprecedented stability with regards to olefin functionalisation. Osmium complexes from related dihydroxylation or amino-hydroxylation are significantly less stable and thereby promote catalytic reactions. This difference in reaction profile has been investigated and chiral osmium heterocycles obtained from olefin difunctionalisation were characterised by X-ray analysis for the first time. Kinetic studies on the reaction profile have also been carried out. An asymmetric version of this reaction is based on chiral non-racemic auxiliaries and leads to diastereomerically enriched osmaimidazolidines with up to 90% de. This sequence represents the first asymmetric diamination of olefins. Attempts on the use of chiral ligands for direct asymmetric diamination as well as the consequences of osmaimidazolidine properties for a catalytic reaction are discussed.
Double asymmetric induction as a mechanistic probe: The doubly diastereoselective conjugate addition of enantiopure lithium amides to enantiopure α,β-unsaturated esters and enantiopure α,β-unsaturated hydroxamates
Davies, Stephen G.,Lee, James A.,Roberts, Paul M.,Thomson, James E.,Yin, Jingda
, p. 6382 - 6403 (2011/09/19)
The doubly diastereoselective conjugate addition of the antipodes of lithium N-benzyl-N-(α-methylbenzyl)amide to a range of enantiopure α,β-unsaturated esters [derived from Corey's 8-phenylmenthol chiral auxiliary] and enantiopure α,β-unsaturated hydroxamates [derived from our 'chiral Weinreb amide' auxiliary (S)-N-1-(1′-naphthyl)ethyl-O-tert- butylhydroxylamine] has been used as a mechanistic probe to determine the reactive conformations of these acceptors.
Highly diastereoselective synthesis of vinylcyclopropane derivatives with (-)-8-phenylmenthol as chiral auxiliary
Ye,Tang,Dai
, p. 5717 - 5722 (2007/10/03)
The silylated telluronium allylide 4, generated in situ from the corresponding telluronium salt in the presence of LiTMP, reacted with (-)-8-phenylmenthyl α,β-unsaturated esters to afford trans-2-silylvinyl-trans-3-substituted cyclopropyl esters with high diastereoselectivity in high yields. The absolute configuration was determined by chemical transformation. A mechanistic rationale is proposed.
Diastereoselectivity in the Preparation of β-Silyl Esters from αβ-Unsaturated Esters and Amides Attachhed to Chiral Auxiliaries
Fleming, Ian,Kindon, Nicolas D.
, p. 303 - 316 (2007/10/02)
The conjugate addition of the phenyldimethylsilyl-cuprate reagent to cinnamate and crotonate esters and amides 1 of various known chiral auxiliaries, a-e, is diastereoselective.The sense of diastereoselectivity of silyl-cuprate addition to the esters 1b-d, 8 and 9 is different from established precedent based on carbon-cuprates, but is normal for silyl-cuprate addition to the amide 1a, the imines 1e and 21, and the oxazolidine 6.The chiral auxiliary e gives the best results of those tested, and the silicon-containing group can be removed from the chiral auxiliary using alkoxide ion in aprotic media, making available β-silyl esters 27-29 of high enantiomeric excess, with recovery of the chiral auxiliary 30.
