In order to develop an efficient organocatalyst for the enantioselective N-H insertion reaction via carbene/carbenoid, the catalytic core of the cinchona alkaloids was investigated. According to our working hypothesis of an eight-membered ring transition state in the N-H insertion reaction, two pairs of enantiomers related to 2-amino-1-phenylethanol were investigated for their chiral inducing potential. Since both (1R,2S)-isomers gave the N-phenyl-1-phenylglycine derivative enriched in the R-form, while their enantiomers gave the S-form, the 2-amino-1-phenylethanol structure is concluded to be the catalytic core of the cinchona alkaloid in the enantioselective N-H insertion reaction via rhodium(II) carbenoid.
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http://dx.doi.org/10.1248/cpb.c18-00795 | DOI Listing |
Chem Asian J
December 2024
Department of Chemistry, Indian Institute of Technology Madras, Chennai, 600036, Tamilnadu, India.
We disclosed an efficient protocol for regioselective C6 C-H/N-H activation/annulation reaction of indole-7-carboxamides with alkynes to synthesize highly substituted pyrrolo[3,2-h]isoquinolin-9-one derivatives. Under optimized reaction conditions, electron-deficient and electron-rich internal alkynes reacted efficiently with various indole-7-carboxamides to deliver desired products in good to excellent yields. The synthetic utility of the product is demonstrated by its selective oxidation to the corresponding isatin derivative.
View Article and Find Full Text PDFJ Chem Phys
December 2024
Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, India.
Herein, we have investigated the effect of microhydration on the secondary structure of a capped dipeptide Boc-DPro-Gly-NHBn-OMe (Boc = tert-butyloxycarbonyl, Bn = Benzyl), i.e., Pro-Gly (PG) with a single H2O molecule using gas-phase laser spectroscopy combined with quantum chemistry calculations.
View Article and Find Full Text PDFJ Org Chem
December 2024
Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States.
A novel iridium-catalyzed [3 + 2] annulation of naphthylamines and α-diazocarbonyl compounds was developed for the rapid assembly of densely functionalized indoles. This new catalytic process represents the first example of a cascade intramolecular nucleophilic cyclization by the N-H insertion of amines. Various naphthylamines and α-diazocarbonyl compounds could be obtained in high yields with excellent functional group tolerance.
View Article and Find Full Text PDFJ Org Chem
November 2024
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India.
Chemoselective insertion of in situ generated α-imino rhodium carbene onto the O-H bond of 2-aminobenzyl alcohols over the N-H bond followed by [1,3]-alky shift has been successfully accomplished for the synthesis of amine tethered ketone derivatives. The resultant product was further cyclized under acidic conditions to afford biologically important 3-aminoquinolines. Successful integration of chemoselective insertion--rearrangement and cyclization in one pot offered access to various 3-aminoquinolines in a good yield.
View Article and Find Full Text PDFJ Am Chem Soc
November 2024
Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education; Yunnan Key Laboratory of Research and Development for Natural Products; School of Pharmacy, Yunnan University, Kunming 650500, P. R. China.
New methods for the enantioselective synthesis of N-alkylated indoles and their derivatives are of great interest because indoles are pivotal structural elements in biologically active molecules and natural products. They are also versatile intermediates in organic synthesis. Among well-established asymmetric hydroamination methods, the asymmetric hydroamination with indole-based substrates is a formidable challenge.
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