Phospholane‐Phosphite Ligands for Rh Catalyzed Enantioselective Conjugate Addition: Unusually Reactive Catalysts for Challenging Couplings

Abstract

The use of Rh catalysts derived from a phospholanephosphite ligand were found to be more productive than the classic rhodium/BINAP system in enantioselective conjugate additions. These catalysts enable the use of lower amounts of aryl boronic acid in an asymmetric arylation reaction that required [a] Dr. ane-phosphite, L1, known as BOBPHOS, [11] gives enhanced reactivity relative to the use of BINAP as the ligand and enabled the preparation of some of the compounds that couldn't be easily be made following standard Rh/BINAP promoted protocols.

Ligand Hydrogenation during Hydroformylation Catalysis Detected by In Situ High-Pressure Infra-Red Spectroscopic Analysis of a Rhodium/Phospholene-Phosphite Catalyst

“…The latter confer very unusual branched regioselectivity up to 6:1 in the hydroformylation of a range of unbiased terminal ‘alkyl-alkenes’, a type of substrate that normally forms linear aldehydes [ 12 , 13 , 14 , 15 ]. Phospholane-phosphites of this type have also recently been found to be preferred ligands for certain enantioselective arylation reactions using arylboron reagents [ 16 , 17 ].…”

Palladium Catalyzed Enantioselective Hayashi–Miyaura Reaction for Pharmaceutically Important 4-Aryl-3,4-dihydrocoumarins

“…These advances were mainly showcased by the utilization of (R)- Segphos, 9 MeO-F 12 -BIPHEP and its analogue L1, 10 (S)-BICMAP catalysts, 11 Chiraphos, 12 and the air-sensitive phospholane phosphite ligand (R,R,R)-BOBPHOS. 13 Additionally, some chiral diene ligands, such as L2 14 and L3, 15 were also applied specifically.…”

“…From a historical point of view, asymmetric addition of arylboronic acids to coumarins has mainly been realized by rhodium catalysis which was characterized by the development of various chiral biphosphorus ligands (Figure B-1). These advances were mainly showcased by the utilization of ( R )-Segphos, MeO-F 12 -BIPHEP and its analogue L1 , ( S )-BICMAP catalysts, Chiraphos, and the air-sensitive phospholane phosphite ligand ( R , R , R )-BOBPHOS . Additionally, some chiral diene ligands, such as L2 and L3 , were also applied specifically.…”

“…Notwithstanding some promising achievements, the aforementioned rhodium catalytic approaches encountered many challenges in view of synthetic feasibility and economy , or the compatibility of electron-donating coumarins or electron-deficient or ring-fused arylboronic acids . Therefore, the discovery of novel catalytic systems with operational simplicity and facile accessibility is highly desirable for addressing these problematic issues.…”

Palladium Catalyzed Enantioselective Hayashi-Miyaura Reaction for Pharmaceutically Important 4-Aryl-3,4-Dihydrocoumarins

“…These advances were mainly showcased by the utilization of (R)-Segphos, 14 (MeO-F12-BIPHEP), 15 modified BIPHEP 14 16 , (S)-BICMAP catalysts, 17 Chiraphos 18 and the air-sensitive phospholane phosphite ligand (R, R, R)-BOBPHOS from multistep synthesis. 19 Additionally, some chiral diene ligands, such as ligand 15 20 and ligand 16 21 were also applied specifically.…”