@article { ISI:000331163900002, title = {Asymmetric vinylogous mannich reaction of silyloxy furans with N-tert-butanesulfinyl ketimines}, journal = {Organic Letter}, volume = {16}, number = {3}, year = {2014}, month = {FEB}, pages = {648-651}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A highly regio- and diastereoselective TMSOTf promoted vinylogous Mannich reaction for the synthesis of chiral quaternary 3-aminooxindole butenolides from 2-silyloxy furans and chiral ketimines is described. The method is found to be very efficient and also provides a facile access to sterically challenging 3-aminooxindole butenolides bearing two quaternary centers in continuation. Further, the versatility of the method is demonstrated by the 1,4-addition of nucleophiles on the sterically congested butenolide substructure..

}, issn = {1523-7060}, doi = {10.1021/ol4037117}, author = {Rao, V. U. Bhaskara and Jadhav, Amol P. and Garad, Dnyaneshwar N. and Singh, Ravi P.} } @article { ISI:000360398900018, title = {Asymmetric vinylogous michael reaction of cyclic enones with silyloxy furans}, journal = {Chemical Communications}, volume = {51}, number = {73}, year = {2015}, month = {JUL}, pages = {13941-13944}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The asymmetric vinylogous Michael reaction of cyclohexenone/medium and large cyclic enones with 2-silyloxyfuran is still a synthetic challenge. In this report, we have explored 1,4-conjugate addition of an enantioselective chiral, primary diamine catalyzed, 2-silyloxy furan to various cyclic enones and beta-substituted cyclic enones. The reaction provided syn-Michael adducts (cycloalkane connected gamma-butenolide) with good yields, diastereo and enantioselectivities. Furthermore, the synthetic potential of these syn-Michael adducts is demonstrated by 1,4-addition of nucleophiles on the butenolide substructure.

}, issn = {1359-7345}, doi = {10.1039/c5cc05617a}, author = {Jadhav, Amol P. and Rao, V. U. Bhaskara and Singh, Pradeep and Gonnade, Rajesh G. and Singh, Ravi P.} } @article { ISI:000352630600044, title = {Ligand-promoted intramolecular dehydrogenative cross-coupling using a Cu catalyst: direct access to polycyclic heteroarenes}, journal = {Chemical Communications}, volume = {51}, number = {32}, year = {2015}, month = {MAR}, pages = {7065-7068}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A copper(II)-promoted intramolecular C-H coupling reaction between indole-2 and imidazole-2 moieties has been developed for polycyclic heteroarene synthesis. The method provides direct access to biheteroaryl incorporated polycyclic frameworks, which are of huge interest in the area of functional materials and drug-discovery.

}, issn = {1359-7345}, doi = {10.1039/c5cc01817j}, author = {Ray, Devalina and Manikandan, T. and Roy, Arup and Tripathi, Krishna N. and Singh, Ravi P.} } @article { ISI:000379456500042, title = {Intramolecular dehydrogenative coupling of 2,3-diaryl acrylic compounds: access to substituted phenanthrenes}, journal = {Journal of Organic Chemistry}, volume = {81}, number = {13}, year = {2016}, month = {JUL}, pages = {5663-5669}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A simple, facile, and environmentally benign intramolecular dehydrogenative coupling of various 1,2-diarylethylenes for the synthesis of phenanthrenes in excellent yield has been described. This new methodology uses ceric ammonium nitrate (CAN) as a promoter at room temperature and has been extended to intermolecular synthesis of biaryl compounds. The electron transfer from methoxyarene to cerium leads to cationic radical formation, which further proceeds to intramolecular coupling. Preliminary mechanistic investigation by EPR spectroscopy and density functional theory calculation suggested a similar view.

}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b00507}, author = {Gupta, Vijay and Rao, V. U. Bhaskara and Das, Tamal and Vanka, Kumar and Singh, Ravi P.} } @article {46322, title = {Diastereoselective multi-component tandem condensation: synthesis of 2-amino-4-(2-furanone)-4H-chromene-3-carbonitriles}, journal = {Organic \& Biomolecular Chemistry}, volume = {17}, year = {2019}, month = {OCT}, pages = {8853-8857}, type = {Article}, abstract = {

A general strategy for a one-pot stereoselective synthesis of 2-amino-4-(2-furanone)-4H-chromene-3-carbonitriles by reaction of salicylaldehyde, malononitrile and butenolides via a tandem Knoevenagel/Pinner/vinylogous Michael condensation is presented. The beta,gamma-butenolides gave a syn-selective MCR adduct with a dr up to 11.5 : 1. The mechanistic insight into the MCR was obtained by DFT calculations.

}, issn = {1477-0520}, doi = {10.1039/c9ob01345h}, author = {Gupta, Vijay and Sahu, Debashish and Jain, Shailja and Vanka, Kumar and Singh, Ravi P.} } @article {46936, title = {Palladium-catalyzed oxidative annulation of pyrrolylalkyl-1H-azoles: towards the synthesis of polyheterocyclic arenes}, journal = {Synthesis-Stuttgart}, volume = {52}, year = {2020}, month = {MAR }, pages = {719-726}, type = {Article}, abstract = {

A highly efficient and regioselective palladium-catalyzed annulation protocol for a series of linear and terminally substituted 1,2- and 1,3-di(heteroaryl)alkanes to the corresponding polyheterocyclic arenes is reported. Herein, intramolecular oxidative coupling involving double C(sp(2))-H bond functionalization provides a feasible access to biheteroaryl systems annulated to a six-membered ring. The methodology is not restricted to six-membered annulations and was extended to the synthesis of compounds with a seven-membered ring and biheteroaryl core.

}, keywords = {C-H functionalization, imidazoles, oxidative coupling, Palladium, pyrroles}, issn = {0039-7881}, doi = {10.1055/s-0039-1691492}, author = {Tripathi, Krishna N. and Bansode, Avinash H. and Singh, Ravi P.} } @article {46718, title = {Vinylogous michael addition of 3-alkylidene-2-oxindoles to beta,gamma-unsaturated alpha-keto esters by bifunctional cinchona alkaloids}, journal = {European Journal of Organic Chemistry}, volume = {2020}, year = {2020}, month = {SEP }, pages = {5690-5694}, type = {Article}, abstract = {

A highly enantioselective vinylogous Michael addition of 3-alkylidene-2-oxindoles with beta,gamma-unsaturated alpha-keto esters using a bifunctional tertiary-amine thiourea catalyst is demontsrated. The challenging Michael reaction with the beta,gamma-unsaturated alpha-keto esters has been accomplished due to the synchronized H-bond guided dual activation of vinylogous nucleophile and electrophile by catalyst. The reaction afforded product in high yield while resulting in excellent stereocontrol (\> 19:1E/Zand upto 99 \%ee).

}, keywords = {3-Alkylidene-2-oxindoles, Asymmetric synthesis, beta, gamma-Unsaturated alpha-keto esters, Michael adduct, Vinylogous Michael addition}, issn = {1434-193X}, doi = {10.1002/ejoc.202000835, Early Access Date = SEP 2020}, author = {Jaiswal, Manish K. and Kumar, Rajesh and Singh, Sanjay and Jain, Shailija and Vanka, Kumar and Singh, Ravi P.} }