A Unified Strategy for the Asymmetric Synthesis of Highly Substituted 1,2-Amino Alcohols Leading to Highly Substituted Bisoxazoline Ligands
作者:Bijay Shrestha、Brennan T. Rose、Casey L. Olen、Aaron Roth、Adon C. Kwong、Yang Wang、Scott E. Denmark
DOI:10.1021/acs.joc.0c02899
日期:2021.2.19
A general procedure for the asymmetric synthesis of highly substituted 1,2-amino alcohols in high yield and diastereoselectivity is described that uses organometallic additions of a wide range of nucleophiles to tert-butylsulfinimines as the key step. The addition of organolithium reagents to these imines follows a modified Davis model. The diastereoselectivity for this reaction depends significantly
A Silicon Tether Approach for Addition of Functionalized Radicals to Chiral α-Hydroxyhydrazones: Diastereoselective Additions of Hydroxymethyl and Vinyl Synthons
作者:Gregory K. Friestad、Sara E. Massari
DOI:10.1021/jo035405r
日期:2004.2.1
Stereocontrolled additions of hydroxymethyl and vinyl groups to chiral α-hydroxyhydrazones can be achieved by radical cyclizations using bromomethyl or vinyl radical precursors tethered via a temporarysiliconconnection. Tin-mediated 5-exo radical cyclization of α-hydroxyhydrazones using a silicon-tethered bromomethyl group, followed by oxidative removal of the tether, provides anti-2-hydrazino 1
olefinic stereo-, and diastereoselective addition to aldehydes to give virtually single allyl alcohols. Alternatively, inter- or intramolecular coupling reaction between N-(1-alkynyl)sulfonamides and another acetylene or olefin with the above titanium alkoxide reagent generated the corresponding titanacycles, hydrolysis of which furnished stereo-defined (sulfonylamino)dienes or cyclic compounds.
Stereoselective Allylic Alkylations of Amino Ketones and Their Application in the Synthesis of Highly Functionalized Piperidines
作者:Cynthia Prudel、Kai Huwig、Uli Kazmaier
DOI:10.1002/chem.202000051
日期:2020.3.9
Chelated ketone enolates are excellent nucleophiles for allylic alkylations. Electron-withdrawing groups on the allyl moiety allow subsequent intramolecular Michael additions giving rise to piperidines with up to five stereogenic centers.
Ether-directed diastereoselectivity in catalysed Overman rearrangement: comparative studies of metal catalysts
作者:Ieva Jaunzeme、Aigars Jirgensons
DOI:10.1016/j.tet.2008.03.099
日期:2008.6
Ether-directed diastereoselectivity in Overman rearrangement of delta-methoxy and delta-TBDMSO substituted allylic trichloroacetimidates has been explored using PtCl2, PtCl4, AuCl and AuCl3 catalysts in comparison with commonly used Pd(II) catalysts. For both substrates the use of PtCl2 catalyst gave notably improved anti/syn-ratio of 1,2-aminoalcohol derivatives (anti/syn=11:1 for 5-methoxy; 6:1 for delta-TBDMSO) compared to all metal catalysts known to promote Overman rearrangement. Formation of 2-trichloromethyloxazoline was observed as a dominant side reaction in the metal catalysed rearrangement of a-methoxy substituted allylic trichloroacetimidates considerably reducing the yield of the desired product. This side reaction was suppressed when delta-TBDMS-ether was used as a directing group. (C) 2008 Elsevier Ltd. All rights reserved.