@article {46995, title = {Highly enantioselective synthesis of sitagliptin}, journal = {Asian Journal of Organic Chemistry}, volume = {9}, year = {2020}, month = {FEB}, pages = {189-191}, type = {Article}, abstract = {

A highly enantioselective synthesis of sitagliptin, a potent DPP-4 inhibitor, is reported. Explicitly identified chiral FerroLANE ligands in the presence of rhodium catalyze the asymmetric hydrogenation of an enamine to yield sitagliptin with excellent enantioselectivity (98\% ee). The process was scaled up to 5 g and the final product was isolated as a phosphate salt with \>99\% ee.

}, keywords = {asymmetric hydrogenation, catalysis, FerroLANE ligands, Rhodium, sitagliptin}, issn = {2193-5807}, doi = {10.1002/ajoc.201900709, Early Access Date = JAN 2020}, author = {Khopade, V. Kishor and Sen, Anirban and Birajdar, Rajkumar S. and Paulbudhe, Uday P. and Kavale, Dattatry S. and Shinde, Prashant S. and Mhaske, Santosh B. and Chikkali, Samir H.} } @article {47899, title = {Mechanistically guided one pot synthesis of phosphine-phosphite and its implication in asymmetric hydrogenation}, journal = {European Journal of Organic Chemistry}, volume = {2022}, year = {2022}, month = {JAN}, pages = {e202101447}, type = {Article}, abstract = {

Although hybrid bidentate ligands are known to yield highly enantioselective products in asymmetric hydrogenation (AH), synthesis of these ligands is an arduous process. Herein, a one pot, atom-economic synthesis of a hybrid phosphine-phosphite (L1) is reported. After understanding the reactivity difference between an 0-nucleophile versus C-nucleophile, one pot synthesis of Senphos (L1) was achieved (72\%). When L1 was treated with [Rh], P-31 NMR revealed bidentate coordination to Rh. Senphos, in the presence of rhodium, catalyzes the AH of Methyl-2-acetamido-3-phenylacrylate and discloses an unprecedented turn over frequency of 2289, along with excellent enantio-selectivity (92\%). The generality is demonstrated by hydrogenating an array of alkenes. The AH operates under mild conditions of 1-2 bar H-2 pressure, at room temperature. The practical relevance of Ll is demonstrated by scaling-up the reaction to 1 g and by synthesizing DOPA, a drug widely employed for the treatment of Parkinson{\textquoteright}s disease. Computational insights indicate that the R isomer is preferred by 3.8 kcal/mol over the S isomer.

}, keywords = {asymmetric hydrogenation, catalysis, DOPA synthesis, One pot synthesis, Phosphine-phosphite ligand}, issn = {1434-193X}, doi = {10.1002/ejoc.202101447}, author = {Sen, Anirban and Kumar, Rohit and Pandey, Swechchha and Raj, K. Vipin and Kumar, Pawan and Vanka, Kumar and Chikkali, Samir H.} } @article {48925, title = {Rh-catalyzed asymmetric hydroformylation of olefins using phosphorus ligands}, journal = {Journal of chemical sciences }, volume = {135}, year = {2023}, month = {NOV }, pages = {108}, type = {Article}, abstract = {

Easily accessible BINOL-based monodentate phosphite ligand L1 and hybrid ligand L2 have been synthesized in good yield by following a one-pot, two-step protocol. A single 31P resonance at 146.6 ppm confirmed the formation of L1. Subsequent 1-2D NMR and mass spectrometric analysis authenticated the existence of L1. These ligands afforded excellent activity and regio-selectivity in the Rh-catalyzed AHF of styrenic substrates. L1 showed excellent regioselectivity but did not discriminate between the two enantiomers, while L2 displayed an enantiomeric excess (ee) of up to 20\%. In our attempts to understand the reasons for low ee, the coordination behavior of L2 was investigated. The coordination study revealed that L2 coordinates with the Rh as a monodentate ligand, although there are two P-sites. It was found that only the phosphine arm was coordinated to the Rh and the phosphite arm stayed away from the Rh core at the ambient temperature, leading to moderate ee.Graphical abstractOne-step synthesis of a phosphite (L1) and a phosphine-phosphite (L2) ligand and their implication in the asymmetric hydroformylation of olefins with excellent regioselectivity (\>95\%) and moderate enantioselectivity (up to 20\%) is reported.

}, keywords = {catalysis, coordination, Hydroformylation, Phosphine-phosphite ligand, Phosphite ligand}, issn = {0974-3626}, doi = {10.1007/s12039-023-02227-5}, author = {Kumar, Rohit and Sen, Anirban and Chikkali, Samir H.} }