Heavyweight “R-SMS-Phos” Ligands in the Olefins’ Hydrogenation Arena

Abstract

A series of enantiopure P-stereogenic 1,2-bis[(o-RO-phenyl)(phenyl)phosphino]ethane (R-SMS-Phos) ligands wherein R = i-Pr, i-Bu, t-Bu, 3-Pen, and CH(2)TMS was assessed in the Rh(I)-catalyzed hydrogenation of an indicative set of olefins. The best performing t-Bu-SMS-Phos ligand was screened against a wide range of representative classes of standard and new olefinic substrates such as dehydroamido esters, dehydro-alpha-amido-phosphonates, enamides, itaconates, acrylates, enol acetates, alpha-phosphonovinyl benzoates, alpha-(2-pyridyl N-oxide)styrenes, and alpha-(1-hydroxyliminoethyl)styrenes. Excellent enantioselectivities and high TOFs were attained under mild conditions.

Nickel(II) and Palladium(II) Complexes of the Small-Bite-Angle P-Stereogenic Diphosphine Ligand MaxPHOS and Its Monosulfide

“…Less frequent are those phosphines whose chirality is due to the existence of asymmetrically substituted phosphorus atoms, a family known as P-stereogenic ligands. This type of ligand has a long history in homogeneous catalysis, which can be traced back to the influential work of Knowles and co-workers with PAMP and DiPAMP in the 1970s in asymmetric hydrogenation to produce the drug l -DOPA. , Since then, newer synthetic methods based on the use of phosphine–boranes as versatile synthetic intermediates − have allowed the preparation of a new generation of P-stereogenic ligands, prompting a renaissance of the field. − Some of these new ligands, represented in Figure , have been found to be extremely efficient in Rh-catalyzed asymmetric hydrogenation and other catalytic reactions. − …”

Recent Advances in the Enantioselective Synthesis of Chiral Amines via Transition Metal-Catalyzed Asymmetric Hydrogenation

“…Stephan's laboratory performed the rhodium-catalyzed AH of a wide spectrum of representative enamides using L32 and L33 (SMS-Phos) as chiral ligands. 275,276 Both catalytic systems showed excellent enantioselectivities (>99% ee for several model substrates; Table 1). The catalytic activity of the ligand was markedly affected by the nature of its aryl substituents in terms of both bulkiness and electronic properties.…”

P-Stereogenic Phosphorus Ligands in Asymmetric Catalysis

“…It should be noted that very high enantioselectivities (>98% ee) have been observed in many cases, especially when employing electronrich and conformationally rigid ligands. Furthermore, significantly high turnover numbers (TONs) (>10 000) have been achieved in the hydrogenations with TangPhos, 40 DiSquar-eP*, 171 SMS-Phos, 184 BenzP*, 189 TMB-QuinoxP*, 196 2i-PrBigFUS, 219 POP, 235 and L79. 236 These results suggest that analogous electron-rich ligands such as TCFP, 41 DuanPhos, 42 ZhangPhos, 186 and BulkyP* 252 may exhibit similarly high TONs.…”