Reactivity Enhancement for Chiral Dirhodium(II) Tetrakis(Carboxamidates)

Development of Dirhodium(II)-Catalyzed Generation and Enantioselective 1,3-Dipolar Cycloaddition of Carbonyl Ylides

“…Although carboxamidate catalysts might be anticipated to be somewhat unreactive towards diazo decomposition with doubly stabilised diazo compounds such as 2, the well-known commercially available glutamic-acid-derived catalyst [Rh 2 {(R)-mepy} 4 ] (7; mepy methyl 2-pyrrolidine 5-carboxylate anion), [3,16] the more reactive azetidine-based catalyst 8 [17] and the difluorinated catalyst 9 [18] all generated cycloadduct 2, albeit with no optical activity. The mandelic-acidderived catalysts 10 and 11, were two of the first reported examples of chiral Rh II catalysts, [19,20] the former generating the highest levels of asymmetric induction (45 % ee) in a study by McKervey et al of enantioselective NÀH insertion.…”

N-H Insertion reactions of rhodium carbenoids. Part 4. New chiral dirhodium(II) carboxylate catalysts

“…13 Finally, we investigated four catalysts 15-18 identified using our parallel synthesis catalyst screen for new Si-H insertion catalysts, 12 and three new catalysts 19-21, also based on N-arenesulfonylamino acids ( Figure 1). These new catalysts were prepared by reaction of the appropriate N-arenesulfonyl amino acid with dirhodium(II) carbonate.…”

“…In view of our own interest in the development of novel chiral dirhodium(II) catalysts, [10][11][12][13] we now report the results of our attempts to effect stereoselective N-H insertion reactions of rhodium carbenes derived from diazoesters and diazophosphonates.…”

Approaches to Obtaining Fluorinated α-Amino Acids

“…186 Oxidation of the primary alcohol with Jones reagent and formation of the methyl ester using diazomethane yielded the desired (2S)-4,4-difluoropyroglutamate derivative 295 (Scheme 63). 191 4.3.6. 3-Substituted Prolines.…”