No 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.

Insertion or coordination copolymerization of ethylene with di‐substituted olefins is challenging and the choice of di‐substituted mono‐functional olefin versus di‐substituted di‐functional olefin (DDO) appears to be decisive. Here we show that DDO‐inserted species are amenable to ethylene insertion and polymerization. DDOs such as 2‐acetamidoacrylic acid (AAA), methyl 2‐acetamidoacrylate (MAAA), and ethyl 2‐cyanoacrylate (ECA) were treated with palladium complex [{P∧O}PdMe(L)] (P∧O=κ2‐P,O−Ar2PC6H4SO2O with Ar=2‐MeOC6H4; L=C2H6OS) and the existence of respective insertion intermediates in moderate yield (up to 37 %) was established. These intermediates were exposed to ethylene and corresponding ethylene‐inserted products were isolated and characterized. A careful comparison with three model compounds confirmed ethylene insertion and polymerization. Thus, the combined experimental and computational investigations show that DDO‐inserted species can undergo ethylene insertion and polymerization.