The search for an easily-prepared sparteine surrogate
作者:Vera M. Foley、Rafael Cano、Gerard P. McGlacken
DOI:10.1016/j.tetasy.2016.09.001
日期:2016.12
(-)-Sparteine has proven itself to be a highly efficient and versatile ligand. However, in recent years it has become difficult to source. In addition the (+)-enantiomer is also not readily available. Here we report a suite of chiral diamines as potential sparteine surrogates. Chiral trans-1,2-diaminocyclohexane is commercially available in both enantiomeric forms and the parent structure can be easily modified. New (and known) chiral diamines have been tested in the asymmetric silylation of N-Boc pyrrolidine, N-Boc piperidine, the alpha-alkylation of dimethylhydrazones and in the rearrangement of meso-epoxides. While none match the selectivity of the highly evolved natural product, there is certainly potential for this class of diamine ligands to perform in a diverse set of asymmetric transformations. (C) 2016 Elsevier Ltd. All rights reserved.
作者:Iain Coldham、Sophie Raimbault、Praful T. Chovatia、Jignesh J. Patel、Daniele Leonori、Nadeem S. Sheikh、David T. E. Whittaker
DOI:10.1039/b810988e
日期:——
Dynamic thermodynamic resolution of N-Boc-2-lithiopiperidine is possible using a chiral ligand; the two enantiomers of this organolithium can be resolved with selectivities of up to 85 : 15 from a selection of 26 chiral diamino-alkoxide ligands screened.
Highly Enantioselective Catalytic Dynamic Resolution of <i>N</i>-Boc-2-lithiopiperidine: Synthesis of (<i>R</i>)-(+)-<i>N-</i>Boc-Pipecolic Acid, (<i>S</i>)-(−)-Coniine, (<i>S</i>)-(+)-Pelletierine, (+)-β-Conhydrine, and (<i>S</i>)-(−)-Ropivacaine and Formal Synthesis of (−)-Lasubine II and (+)-Cermizine C
作者:Timothy K. Beng、Robert E. Gawley
DOI:10.1021/ja105772z
日期:2010.9.8
syntheses of both enantiomers of 2-substituted piperidines using a wide range of electrophiles. The CDR has been applied to the synthesis of (R)- and (S)-pipecolic acid derivatives, (+)-beta-conhydrine, (S)-(+)-pelletierine, and (S)-(-)-ropivacaine and the formal synthesis of (-)-lasubine II and (+)-cermizine C.
An Experimental and Computational Investigation of the Enantioselective Deprotonation of Boc-piperidine
作者:William F. Bailey、Peter Beak、Shawn T. Kerrick、Sunghoon Ma、Kenneth B. Wiberg
DOI:10.1021/ja012169y
日期:2002.3.1
asymmetric deprotonation of N-Boc-piperidine (3) by the 1:1 complex of a sec-alkyllithium and (-)-sparteine has been investigated both experimentally and computationally. The lithiation of 3 with sec-BuL-(-)-sparteine at -78 degrees C, which is a much slower process than is the analogous deprotonation of N-Boc-pyrrolidine (1) and a minor reaction relative to the competing addition of sec-BuLi to the carbamate
Asymmetric Substitutions of 2-Lithiated N-Boc-piperidine and N-Boc-azepine by Dynamic Resolution
作者:Iain Coldham、Sophie Raimbault、David T. E. Whittaker、Praful T. Chovatia、Daniele Leonori、Jignesh J. Patel、Nadeem S. Sheikh
DOI:10.1002/chem.200903059
日期:2010.4.6
(N‐Boc‐piperidine) with sBuLi and TMEDA provides a racemic organolithium that can be resolved using a chiral ligand. The enantiomeric organolithiums can interconvert so that a dynamic resolution occurs. Two mechanisms for promoting enantioselectivity in the products are possible. Slow addition of an electrophile such as trimethylsilylchloride allows dynamic resolution under kinetic control (DKR). This