Highly diastereoselective synthesis of two analogues of dihydrosphingosine
摘要:
Diastereomeric analogues 8 and 9 of dihydrosphingosine 2 with a shortened alkyl chain were obtained with high diastereoselectivity via addition of n-hexyl magnesium bromide or dihexylzinc to a chiral aldehyde 3, respectively. These compounds are precursors of new potentially hydrosoluble analogues of glycosphingolipides. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Synthesis of bis(7-octenyl)zinc via heterogeneous Ni catalysts
摘要:
Grignard, photochemical, or borane-mediated hydrozincation synthetic routes afford non-volatile olefin functionalized bis(alkyl)zincs such as bis(7-octenyl)zinc (1). These traditional methods present limitations in product isolation and process scale-up. A hydrozincation route to synthesize these types of bis(alkyl)zincs utilizing heterogeneous catalysis has been developed from screening commercially available Ni and Rh supported catalysts using diethylzinc and 1-hexene as the olefin substrate. The catalytic hydrozincation process is optimized with the Ni catalysts (at 0.3 wt% Ni) to improve the yield of 1 by removal of ethylene coproduct from the reaction mixture. Process scale-up to 10 g of product is demonstrated with the most active Ni catalyst identified, to afford 1 in moderate yield after facile separation from the catalyst by product filtration. (C) 2014 Elsevier Ltd. All rights reserved.
Reaction of Nitrogen‐Radicals with Organometallics Under Ni‐Catalysis: N‐Arylations and Amino‐Functionalization Cascades
作者:Lucrezia Angelini、Jacob Davies、Marco Simonetti、Laia Malet Sanz、Nadeem S. Sheikh、Daniele Leonori
DOI:10.1002/anie.201900510
日期:2019.4
the generation of nitrogen‐radicals by ground‐state single electron transfer with organyl–NiI species. Depending on the philicity of the N‐radical, two types of processes have been developed. In the case of nucleophilic aminyl radicals direct N‐arylation with aryl organozinc, organoboron, and organosilicon reagents was achieved. In the case of electrophilic amidyl radicals, cascade processes involving
Electrophilic amination of organozinc reagents with acetone O-(2,4,6-trimethylphenylsulfonyl)oxime and O-methylhydroxylamine
作者:Ender Erdik、Tahir Daşkapan
DOI:10.1039/a906093f
日期:——
Reaction of diorganozincs and triorganozincates with acetone O-(2,4,6-trimethylphenylsulfonyl)oxime or O-methylhydroxylamine in the presence of CuCN provides a new one-flask method for electrophilic amination of organozinc reagents. Considering the lithium- or magnesium-to-zinc transmetallation, this method also extends the scope of electrophilic amination of organolithiums and Grignard reagents.
O<sub>2</sub>-Mediated Oxidation of Aminoboranes through 1,2-N Migration
作者:Marian Rauser、Daniel P. Warzecha、Meike Niggemann
DOI:10.1002/anie.201803168
日期:2018.5.14
In analogy to the classical reaction of C−B bonds with peroxides, the first oxidative functionalization of aminoboranes through a 1,2‐N migration was realized. Readily available aliphaticnitrocompounds are thereby transformed into N‐ and O‐functionalized hydroxylamines in a single synthetic operation. Addition of hazardous peroxides is avoided. Instead, the insertion of O2, as the terminal oxidant
Generation of chiral N-acylpyridinium ions by means of silyl triflates and their diastereoselective trapping reactions: formation of N-acyldihydropyridines and N-acyldihydropyridones
作者:Cornelia E Hoesl、Markus Maurus、Jörg Pabel、Kurt Polborn、Klaus Th Wanner
DOI:10.1016/s0040-4020(02)00675-0
日期:2002.8
An efficient method for the generation of chiral N-acylpyridinium salts from various pyridines and a chiral acid chloride promoted by means of silyltriflates as additives is presented. The stereoselectiveaddition of organometallic reagents to the intermediate chiral N-acylpyridinium ions led to α-substituted N-acyldihydropyridines and N-acyldihydropyridones in good yields, whereas no or minor amounts
Formation of Coordinated RZn(macrocycle)<sup>+</sup> Cations and Organozincate Anions from Reactions of Organozinc Compounds and Macrocycles
作者:Ronaldo M. Fabicon、Herman G. Richey
DOI:10.1021/om0102798
日期:2001.9.1
An RZnZ compound (R = alkyl) and a macrocycle react in benzene to form RZn(macrocycle)+ ions when the macrocycle is an effective coordinator for RZn+ and Z- can exist as the anion or become attached to an organometallic acceptor to form an organometalate anion. R2Zn and R3Al form RZn(macrocycle)+R4Al- with 14N4 (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), 15N5 (1,4,7,10,13-pentamethyl-1