Carbon dioxide: a reagent for the simultaneous protection of nucleophilic centres and the activation of alternative locations to electrophilic attack.
作者:Alan R. Katritzky、Wei-Qiang Fan、Kunihiko Akutagawa
DOI:10.1016/s0040-4020(01)87558-x
日期:1986.1
N-Methyl- and M-ethyl-aniline are regiospecifically converted into a range of ortho-substituted derivatives, using carbondioxide both for M-protection and as an intermediate carbanion stabilizing group, and -butyllithium to lithiate the ortho-carbon atom. The resulting lithium N-(ortho-substituted-phenyl)-N-methyl- and -N-ethyl-carbamates undergo smooth acid-catalysed decarboxylation under mild conditions
Chemoselectivity for Alkene Cleavage by Palladium-Catalyzed Intramolecular Diazo Group Transfer from Azide to Alkene
作者:Grant B. Frost、Michaela N. Mittelstaedt、Christopher J. Douglas
DOI:10.1002/chem.201805904
日期:2019.2.1
Alkenes can be cleaved by means of the (3+2) cycloaddition and subsequent cycloreversion of 1,3‐dipoles, classically ozone (O3), but the azide (R−N3) variant is rare. Chemoselectivity for these azide to alkene diazo group transfers (DGT) is typically disfavored, thus limiting their synthetic utility. Herein, this work discloses a palladium‐catalyzed intramolecular azide to alkene DGT, which grants
palladium-catalyzed intramolecular hydroaminocarbonylation of 2-(1-methylvinyl)aniline derivatives has been achieved using dppp (1,3-bis(diphenylphosphino)propane) as a ligand under hydrogen-free conditions. The reaction involves the generation of an active palladium hydride species with a catalytic amount of TsOH. This amide bond formation reaction was applied to the synthesis of various 4-substituted 3,4-dihydroquinolone
Rotational features of carbon-nitrogen bonds in axially chiral o-tert-butyl anilides and related molecules. Potential substrates for the ‘prochiral auxiliary’ approach to asymmetric synthesis
作者:Dennis P. Curran、Gregory R. Hale、Steven J. Geib、Aaron Balog、Quezia B. Cass、Ana Luiza G. Degani、Marcelo Z. Hernandes、Luiz Carlos G. Freitas
DOI:10.1016/s0957-4166(97)00599-5
日期:1997.12
A new strategy for asymmetric induction termed the 'prochiral auxiliary' approach is introduced. Reactions of acylating agents with prochiral N-methyl-o-tert-butyl aniline provide anilides that are axially chiral by virtue of restricted rotation about the N-Ar bond, Rotamer populations about the amide bond (E/Z) were studied by H-1 NMR. Several pairs of enantiomeric o-tert-butyl anilides were separated by chiral chromatography and barriers about the N-Ar bond were measured by thermal racemization. Related o-(1-(trialkylsilyloxy)-1-methylethyl) anilides were also studied. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.