Rhodium‐Catalyzed Asymmetric 1,4‐Additions, in Water at Room Temperature, with In‐Flask Catalyst Recycling

Abstract

Using the newly introduced designer surfactant polyethyleneglycol ubiquinol sebacate (PQS), as the platform for micellar catalysis, nonracemic BINAP has been covalently attached and rhodium(I) inserted to form PQS-BINAP-Rh. This species, the first example of a nonracemically-ligated transition metal catalyst-tethered amphiphile, can be utilized for Rh-catalyzed asymmetric conjugate addition reactions of arylboronic acids to acyclic and cyclic enones. These are performed in water at room temperature, while the catalyst can be recycled without its removal from water in the reaction vessel.

On the Way Towards Greener Transition‐Metal‐Catalyzed Processes as Quantified by E Factors

“…The overall E Factor, therefore, when no additional water has been added in the workup, and based on this single recycle, drops to 2.4. Tellingly, the measured analytical loss of this valued transition metal, as found within the product ketone in a previous study, [30] was less than 10 ppb.…”

“…[30] From the standpoint of E Factors, a literature example involving such a 1,4-addition of a boronic acid is shown in Scheme 5. [31] Aside from the use of dimethylacetamide (DMA) and the input of external energy to achieve a reaction temperature of 140°C, the associated traditional organic-solvent-based E Factor is almost 23.…”

Rh-catalyzed asymmetric 1,4-addition reactions to α,β-unsaturated carbonyl and related compounds: an update

“…234 Based on the results of these 1,4-additions and the characterization of Rh/(S)-L62a complex by single crystal X-ray crystallography, a stereoselective route was suggested for the 1,4-addition of phenylboronic acid to 2-cyclohexenone under Rh/(S)-L62a catalysis as illustrated in Figure 12a. [235][236][237][238][239][240][241] As shown, the phenylrhodium species had a trans-relationship between the phenyl group and the olefin ligand, while 2-cyclohexenone binds to the rhodium with its si-face at the cis-position of the olefin ligand, resulting in the formation of the 1,4-adduct with an (S)-configuration. The generation of the (R)-product utilizing Rh/(S)-L62d can be explained similarly by the re-face coordination of 2-cyclohexenone to rhodium as depicted in Figure 12b (Tables 74-76).…”

Efficient one-pot synthesis of dihydroquinolinones in water at room temperature

“…In 2012 Lipshutz et al reported an asymmetric rhodium catalyzed 1,4-addition of aryl boronic acids to acyclic and cyclic enones in water at room temperature using the nanomicellar system PQS. 12 In this particular publication chiral BINAP was covalently attached to the PQS surfactant and the rhodium catalyst was subsequently inserted to form the first described chiral transition metal catalyst-tethered surfactant. This alternative to classical organic chemistry is called micellar catalysis: Instead of using organic solvents the reaction is conducted in water containing nanomicelles derived from adding catalytic amounts of commercially available and environmentally benign designer surfactants to the water (e.g.…”