Functionalized Cyclopropanes as Versatile Intermediates for the Diversity-Oriented Synthesis of γ-Lactones, γ-Lactams and δ-Lactams
作者:Marcus M. Sá、Adrielle P. Maximiano、Giovana S. Ramos、Marcelo V. Marques
DOI:10.1055/a-1389-1203
日期:2021.7
A two-step procedure for the preparation of cyclopropanecarboxaldehyde-1,1-diester from a γ,δ-epoxyester and its synthetic versatility are described herein. The epoxide ring-opening/cyclopropanation process occurs in the presence of Mg(ClO4)2 under heating, resulting in cyclopropanemethanol-1,1-diester in 65% yield. A mild TEMPO-mediated oxidation of this substrate readily generated the corresponding
Accessing Dihydro-1,2-oxazine via Cloke–Wilson-Type Annulation of Cyclopropyl Carbonyls: Application toward the Diastereoselective Synthesis of Pyrrolo[1,2-<i>b</i>][1,2]oxazine
作者:Pankaj Kumar、Rakesh Kumar、Prabal Banerjee
DOI:10.1021/acs.joc.0c00531
日期:2020.5.15
A convenient additive-free synthesis of dihydro-4H-1,2-oxazines via a Cloke-Wilson-type ring expansion of the aryl-substituted cyclopropane carbaldehydes with the hydroxylamine salt is introduced. Comparatively less active cyclopropyl ketones also follow a similar protocol if supplemented by catalytic p-toluene sulfonic acid monohydrate. The transformation is performed in an open-to-air flask as it
Lewis Acid-Catalyzed [3+2] Cycloaddition of Donor-Acceptor Cyclopropanes and Enamines: Enantioselective Synthesis of Nitrogen-Functionalized Cyclopentane Derivatives
作者:Kamal Verma、Prabal Banerjee
DOI:10.1002/adsc.201600221
日期:2016.6.30
efficient method for the synthesis of nitrogen‐functionalized cyclopentane derivatives via [3+2] cycloaddition of enamines with donor‐acceptor cyclopropanes in the presence of catalytic amounts of various Lewisacids at room temperature has been developed; furthermore, the corresponding β‐amino acid was synthesized by monodecarboxylation and hydrogenolysis. An enantioenriched synthesis of nitrogen‐functionalized
Lewis Acid Catalyzed Formal [3+2] Cycloaddition of Donor-Acceptor Cyclopropanes and 1-Azadienes: Synthesis of Imine Functionalized Cyclopentanes and Pyrrolidine Derivatives
作者:Kamal Verma、Prabal Banerjee
DOI:10.1002/adsc.201700744
日期:2017.11.10
Lewisacidcatalyzed formal [3+2] cycloadditions of 1-azadienes with donor acceptor cyclopropanes to synthesize varieties of imine functionalized cyclopentanes and pyrrolidine derivatives in moderate to high yield have been developed. Moreover, pharmaceutically relevant azabicyclo[3.2.1]octane, bearing two all-carbon quaternary stereogenic centers at the bridgehead positions, has been synthesized by
Regioselective Tandem Dimethylsulfonium Methylide Addition−Eliminative Olefination of Diendioates: A Novel Route to 1,3-Butadien-2-ylmalonates
作者:Rekha Singh、Sunil K. Ghosh
DOI:10.1021/ol702384s
日期:2007.11.1
The appropriate choice of dimethylsulfoniummethylide generation conditions enables the highly regioselective tandem ylide addition-eliminative olefination to 1,3-dienedioates providing 1,3-butadien-2-ylmalonates, a novel class of 2-substituted 1,3-dienes suitable for quick assembly of precursors for type 2 intramolecular Diels-Alder reactions.