Enantioselective Synthesis of 3,3′‐Diaryl‐SPINOLs: Rhodium‐Catalyzed Asymmetric Arylation/BF₃‐Promoted Spirocyclization Sequence

Abstract

The enantioselective synthesis of a series of C2‐symmetric 3,3′‐diarylated 1,1′‐spirobiindane‐7,7′‐diols (3,3′‐diaryl‐SPINOLs) was developed by sequential Rh‐catalyzed twofold asymmetric conjugate arylation/BF3‐promoted diastereoselective spirocyclization (>20:1 d.r. and >99 % ee for all examples). Some phosphoramidite ligands were prepared from the 3,3′‐Ph‐SPINOL and applied to several catalytic asymmetric reactions, and the 3,3′‐diarylated ligands showed higher enantioselectivities than the privileged nonsubstituted ligands.

Diboron‐Mediated Rhodium‐Catalysed Transfer Hydrogenation of Alkenes and Carbonyls

“…As part of our ongoing efforts on the Rh I ‐catalysed conjugate addition of organoborons to alkenes, we investigated the Rh I ‐catalysed addition of diborons to CF 3 ‐activated alkene 1a , aiming to achieve the conjugate borylation of this β‐aryl‐substituted substrate, which remains a formidable task in borylation of trifluoromethyl alkenes . To our surprise, no conjugate borylation product was detected during our investigation, but reduction of 1a was observed.…”