Design, synthesis and visible-light-induced non-radical reactions of dual-functional Rh catalysts

Planar Chiral Rhodium Complex Based on the Tetrahydrofluorenyl Core for Enantioselective Catalysis

“…Complexes such as [(η 5 -heptamethylindenyl)­RhCl 2 ] 2 and [(η 5 -1-CO 2 Et-2-Me-3-CH 2 Ph-indenyl)­RhCl 2 ] 2 proved to be efficient catalysts for the annulation of benzamides with 3,3-disubstituted cyclopropenes or acetanilides with internal alkynes, respectively. Moreover, Nagashima and Tanaka in their pioneering work demonstrated the versatility of spiro-fluorene-indenoindenyl Rh­(I) complexes as catalysts for visible-light-induced C–H borylation of arenes and [2 + 2 + 2] cycloaddition of alkynes at room temperature . However, the synthesis of these highly substituted indenes requires multistep procedures.…”

“…11 The problem of weak binding of the indenyl ligand can be solved by its functionalization, which has been successfully demonstrated by Rovis 12 and Shibata and Tanaka 13 Rh(I) complexes as catalysts for visible-light-induced C−H borylation of arenes and [2 + 2 + 2] cycloaddition of alkynes at room temperature. 14 However, the synthesis of these highly substituted indenes requires multistep procedures. Recently, we have reported a simple approach to stabilized indenyl rhodium complexes based on 1,2,3,4-tetrahydrofluorene, which is readily available by Benkeser's hydrogenation of fluorene.…”