Copper-Mediated, Heterogeneous, Enantioselective Intramolecular Buchner Reactions of α-Diazoketones Using Continuous Flow Processing
作者:Daniel C. Crowley、Denis Lynch、Anita R. Maguire
DOI:10.1021/acs.joc.8b00147
日期:2018.4.6
intramolecular Buchner reactions of α-diazoketones can be effected using heterogeneous copper–bis(oxazoline) catalysts in batch or using continuousflow processing in up to 83% ee. The catalyst can be reused up to 7 times without loss of activity. For α-diazoketones 3 and 4, the enantioselection achieved in flow with the immobilized catalyst was comparable with the standard homogeneous catalyzed process.
Variation of the enantioselection of the copper-catalysed intramolecular Büchner reaction of diazoketones with the nature of the counterion is reported; significantly the presence of the noncoordinating BARF anion leads to enhanced enantioselectivities when the aryl group bears electron-withdrawing halo substituents.
Electronic effects of aryl-substituted bis(oxazoline) ligands on the outcome of asymmetric copper-catalysed C–H insertion and aromatic addition reactions
作者:Catherine N. Slattery、Sarah O’Keeffe、Anita R. Maguire
DOI:10.1016/j.tetasy.2013.09.009
日期:2013.10
The effect of the modification of bis(oxazoline) ligands on the outcome of copper-catalysed C-H insertion and aromatic addition reactions is described. In general, these reactions display minimum sensitivity in terms of enantiocontrol to variation of the electronic properties of the aryl moiety of the ligand however, some influence is observed for C-H insertions employing naphthyl-substituted bis(oxazolines) and for aromatic addition reactions of biphenyl diazo ketone substrates. The synthesis of the modified bis(oxazolines), which include four novel structures, is also described. (C) 2013 Elsevier Ltd. All rights reserved.
Exploiting Continuous Processing for Challenging Diazo Transfer and Telescoped Copper-Catalyzed Asymmetric Transformations
作者:Daniel C. Crowley、Thomas A. Brouder、Aoife M. Kearney、Denis Lynch、Alan Ford、Stuart G. Collins、Anita R. Maguire
DOI:10.1021/acs.joc.1c01310
日期:2021.10.15
Generation and use of triflyl azide in flow enables efficient synthesis of a range of α-diazocarbonyl compounds, including α-diazoketones, α-diazoamides, and an α-diazosulfonyl ester, via both Regitz-type diazo transfer and deacylative/debenzoylative diazo-transfer processes with excellent yields and offers versatility in the solvent employed, in addition to addressing the hazards associated with handling
Enantioselectivities of up to 95% ee have been achieved in the intramolecular Büchner reaction catalysed by copper bis(oxazoline) complexes, the highest asymmetric inductions reported to date for this transformation. Significantly, use of a catalyst derived from a bis(oxazoline) ligand resulted in high enantioselectivities across several substrates, indicating the possibility of developing a catalyst with general applicability.