Facile Recovery\nand Recycling of a Soluble Dirhodium\nCatalyst in Asymmetric Cyclopropanation via a Catalyst-in-Bag System

A catalyst-in-bag system facilitates the recovery and\nrecycling\nof chiral dirhodium carboxylate catalysts used for enantioselective,\nintermolecular cyclopropanation. The catalyst-in-bag system incorporates\na soluble enantioselective dirhodium complex catalyst within a reusable,\ncommercial dialysis membrane. Dirhodium catalysts of different sizes\nare examined, and two catalysts with molecular weights above 2400\nDa are well-retained by the membrane. The catalyst Rh<sub>2</sub>(<i>S</i>-TPPTTL)<sub>4</sub> [TPPTTL = (1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)-3,3-dimethylbutanoate]\nis explored in enantioselective cyclopropanation reactions under a\nvariety of conditions. The Rh<sub>2</sub>(<i>S</i>-TPPTTL)<sub>4</sub> catalyst, when contained in the catalyst-in-bag system, provides\nhigh yields and enantioselectivities, akin to the homogeneous catalyst\nin solution, with negligible rhodium permeation out of the bag over\nfive catalytic cycles. The catalyst-in-bag approach facilitates recovery\nof the expensive rhodium metal and ligand, with only ppm level Rh\ndetected in the reaction products. The flexible and expandable catalyst-in-bag\nsystem can be accommodated in vessels of different shapes and dimensions.