Carba-Methylephedrine and Carba-pseudo-Methylephedrine as Tools for Probing the Role of the Nitrogen Atom of Chiral Amino Alcohols in Asymmetric Synthesis
Rhodium-Catalyzed Ketone Methylation Using Methanol Under Mild Conditions: Formation of α-Branched Products
作者:Louis K. M. Chan、Darren L. Poole、Di Shen、Mark P. Healy、Timothy J. Donohoe
DOI:10.1002/anie.201307950
日期:2014.1.13
The rhodium‐catalyzed methylation of ketones has been accomplished using methanol as the methylating agent and the hydrogen‐borrowing method. The sequence is notable for the relatively low temperatures that are required and for the ability of the reaction system to form α‐branched products with ease. Doubly alkylated ketones can be prepared from methyl ketones and two different alcohols by using a
A zinc enamide generated from the corresponding N-aryl imine undergoes addition to an unactivatedolefin, such as ethylene, 1-octene, and isobutylene, to generate an alpha-alkylated gamma-zincioimine intermediate in good to excellent yield. Terminal and gem-disubstituted olefins react with >99% regioselectivity, allowing the C-C bond formation to take place at the more hindered carbon of the double
由相应的 N-芳基亚胺生成的锌烯酰胺与未活化的烯烃(例如乙烯、1-辛烯和异丁烯)加成,以良好至极好的收率生成 α-烷基化 γ-锌亚胺中间体。末端和偕二取代的烯烃以>99% 的区域选择性反应,使得 CC 键的形成发生在双键的受阻更大的碳上。有机锌中间体与碳亲电子试剂进一步形成 CC 键,在亚胺水解后,生成带有各种官能化伯、仲和叔烷基的 α-烷基化酮。
Selective Homologation of Ketones and Aldehydes with Diazoalkanes Promoted by Organoaluminum Reagents
作者:Keiji Maruoka、Amel B. Concepcion、Hisashi Yamamoto
DOI:10.1055/s-1994-25682
日期:——
Organoaluminum-promoted single homologation or ring expansion of ketones and aldehydes with diazoalkanes has been described, and among various organoaluminum reagents, exceptionally bulky methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) is found to be highly effective for the selective homologation of various ketones and aldehydes.
Asymmetric Hydrogenation of Unfunctionalized Tetrasubstituted Acyclic Olefins
作者:Raphael Bigler、Kyle A. Mack、Jeff Shen、Paolo Tosatti、Chong Han、Stephan Bachmann、Haiming Zhang、Michelangelo Scalone、Andreas Pfaltz、Scott E. Denmark、Stefan Hildbrand、Francis Gosselin
DOI:10.1002/anie.201912640
日期:2020.2.10
Asymmetrichydrogenation has evolved as one of the most powerful tools to construct stereocenters. However, the asymmetrichydrogenation of unfunctionalized tetrasubstituted acyclic olefins remains the pinnacle of asymmetric synthesis and an unsolved challenge. We report herein the discovery of an iridium catalyst for the first, generally applicable, highly enantio- and diastereoselective hydrogenation
A general and stereoselective method for synthesis of tri- and tetrasubstituted alkenes
作者:I Maciągiewicz、P Dybowski、A Skowrońska
DOI:10.1016/s0040-4020(03)00977-3
日期:2003.8
A convenient, general and stereoselectivesynthesis of trisubstituted alkenes and tetrasubstituted alkenes containing a cyanide function as well as trisubstituted episulphides have been elaborated. Methodology described for the preparation of these compounds is based on the corresponding readily available selenophosphates 1 and thiophosphates 2.