A Sc(OTf)3-catalyzed highly diastereoselective one-pot sequential [3 + 3] dipolar cycloaddition reaction of aldehyde or ketone, N-alkyl hydroxylamine, and spirocyclopropyl oxindole is developed, allowing facile construction of spirocyclic oxindole-tetrahydro-1,2-oxazines with sufficient structural diversity. The corresponding catalytic enantioselective one-pot protocol of aldehydes is also reported
BPh<sub>3</sub>-Catalyzed [2+3] Cycloaddition of Ph<sub>3</sub>PCCO with Aldonitrones: Access to 5-Isoxazolidinones with Exocyclic Phosphonium Ylide Moieties
作者:Amandeep Brar、Daniel K. Unruh、Natalie Ling、Clemens Krempner
DOI:10.1021/acs.orglett.9b02192
日期:2019.8.16
exocyclic phosphonium ylide functionalities via [2+3] cycloaddition of Ph3PCCO and aldonitrones has been developed and applied in the synthesis of 4-alkylidene-5-isoxazolidinones viaWittig olefination. The reaction proceeds by BPh3 catalysis under mild conditions and with a broad substrate scope. A reaction pathway involving the activation of the aldonitrone via interactions with the Lewis acid BPh3 is
Divergent Reaction Pathways of a Cationic Intermediate: Rearrangement and Cyclization of 2-Substituted Furyl and Benzofuryl Enones Catalyzed by Iridium(III)
作者:Tulaza Vaidya、Gerald F. Manbeck、Sylvia Chen、Alison J. Frontier、Richard Eisenberg
DOI:10.1021/ja111317q
日期:2011.3.16
exhibit unusual rearrangement sequences in the presence of catalytic amounts of [IrBr(CO)(DIM)((R)-(+)-BINAP)](SbF(6))(2) (1; DIM = diethylisopropylidene malonate) and AgSbF(6) (1:1). A 1,2-H shift followed by intramolecular Friedel-Crafts alkylation leads to synthetically valuable cyclohexanones with furanylic quaternary centers. The electrophilicity of 1 is essential for this rearrangement.
Origins of Stereoselectivity in the Oxido-Alkylidenation of Alkynes
作者:Daniel P. Canterbury、Alison J. Frontier、Joann M. Um、Paul H.-Y. Cheong、Dahlia A. Goldfeld、Richard A. Huhn、K. N. Houk
DOI:10.1021/ol8019154
日期:2008.10.16
alkynes is described. The three-step sequence involves the 1,3-dipolarcycloaddition of a nitrone and an alkynoate, oxidation of the resulting isoxazoline, and stereoselective extrusion of nitrosomethane. Quantum mechanical calculations identified the interactions of R3 with the oxidant and the preferred conformation of a diradicalintermediate as major factors controlling the stereoselectivity of the
1,3-Dipolar Cycloaddition of
Difluoro(methylene)cyclopropanes with Nitrones: Efficient
Synthesis of 3,3-Difluorinated Tetrahydropyridinols
作者:Ji-Chang Xiao、Xiao-Chun Hang、Qing-Yun Chen
DOI:10.1055/s-2008-1077966
日期:——
Difluoro-substituted spirocyclopropaneisoxazolidines were formed by 1,3-dipolar cycloaddition of difluoro(methylene)cyclopropanes (F 2 MCPs) with nitrones in high yields. The [3+2]-cycloaddition reactions exhibited good regioselectivity and high stereoselectivity. The cycloadducts could rearrange further to form highly substituted 3,3-difluorinated tetrahydropyridinols.