Previously, we have synthesized the title glycine to permit assignment of the prochiral alpha -protons of glycine residues in the NMR study of the protein FKBP. A key, and low yielding step in this synthesis occurs in the ruthenium tetraoxide mediated degradation of N-t-Boc-p-methoxybenzyl amine to N-t-Boc-glycine. Efforts to improve this key step by exploring different substrates and N-protecting groups were successful to render this synthesis amenable for the large scale production of (R)-glycine-d-N-15. (C) 2001 Elsevier Science Ltd. Ail rights reserved.
Iridium-Catalyzed Borylation of Primary Benzylic C–H Bonds without a Directing Group: Scope, Mechanism, and Origins of Selectivity
作者:Matthew A. Larsen、Conner V. Wilson、John F. Hartwig
DOI:10.1021/jacs.5b04899
日期:2015.7.8
Primary benzylic boronate esters are useful intermediates in organic synthesis, but these reagents cannot be prepared by hydroboration. The benzylic C-H borylation of methylarenes would be a method to form these products, but such reactions without neat methylarene or a directing group are unknown. We report an approach to divert the borylation of methylarenes from aromatic positions to benzylic positions
主要的苄基硼酸酯是有机合成中有用的中间体,但这些试剂不能通过硼氢化反应制备。甲基芳烃的苄基 CH 硼酸化将是形成这些产物的一种方法,但这种没有纯甲基芳烃或导向基团的反应是未知的。我们报告了一种以甲硅烷基硼烷为试剂和含有缺电子菲咯啉作为配体的新型铱催化剂将甲基芳烃的硼酸化从芳族位置转移到苄位位置的方法。该系统相对于相应的芳基硼酸酯选择性地形成苄基硼酸酯。由菲咯啉连接的 Ir 二硼基单甲硅烷基复合物被分离并确定为催化剂的静止状态。机理研究表明,这种复合物在动力学上有能力成为催化过程中的中间体。各种 Ir 配合物催化的苄基和芳基 CH 硼化的动力学研究表明,芳基 CH 硼化速率随着 Ir 催化剂金属中心电子密度的降低而降低,但苄基 CH 硼化速率对Ir 催化剂金属中心的电子密度。动力学和计算研究表明,这两种硼酸化反应对金属中心的电子密度程度的反应不同,因为它们发生在不同的转换限制步骤中。已知芳基
One-Pot Synthesis of α-Amino Acids from Imines through CO2 Incorporation: An Alternative Method for Strecker Synthesis
作者:Tsuyoshi Mita、Jianyang Chen、Masumi Sugawara、Yoshihiro Sato
DOI:10.1002/anie.201006422
日期:2011.2.7
It′s a gas: A novel one‐pot process for the synthesis of α‐amino acids from imine equivalents using CO2 gas as a carbon source has been developed. This reaction was made possible by the reagent combination of TMSSnBu3 and CsF (see scheme). Three successive reactions (imine formation, stannylation, and carboxylation) proceeded in the same flask under these conditions to give products in up to 79 % yield
Synthesis and Application of a New Fluorous-Tagged Ammonia Equivalent
作者:Simon D. Nielsen、Garrick Smith、Mikael Begtrup、Jesper L. Kristensen
DOI:10.1002/chem.200903178
日期:2010.4.19
A novel fluorous‐tagged ammoniaequivalent has been developed. It is based on a nitrogen–oxygen bond, which can be cleaved in a traceless manner by a molybdenum complex or samarium diiodide. The application in the synthesis of ureas, amides, sulfonamides, and carbamates is described. The scope of the fluorous NO linker is exemplified by the synthesis of itopride, a drug used for the treatment of functional
Direct Amination of Benzylic Pinacol Boronates by an Aminoazanium
作者:Chao Liu、Jianeng Xu、Yucheng Qin
DOI:10.1055/a-2028-5646
日期:——
A practical stereospecific directamination of benzylic pinacol boronates was achieved by using 4-amino-4-methylmorpholinium iodide as a new amination reagent and cesium carbonate as the base. After amination, an in situ reductive N-alkylation with an aldehyde proceeded well to produce secondary amines.
Chemoselective conversion of azides to t-butyl carbamates and amines
作者:Yeon Joo Jung、Yu Mi Chang、Ji Hee Lee、Cheol Min Yoon
DOI:10.1016/s0040-4039(02)02106-8
日期:2002.11
Azides were converted to the corresponding carbamates using a system of 20 mol% of decaborane (B10H14) and 20 weight% of 10% Pd/C in methanol in the presence of di-tert-butyl dicarbonate at rt in high yields and to the corresponding amines using a system of 10 mol% of decaborane and 20 weight% of 10% Pd/C in methanol in the absence of di-tert-butyl dicarbonate at rt in high yields. (C) 2002 Elsevier Science Ltd. All rights reserved.