New Bisoxazoline Ligands Enable Enantioselective Electrocatalytic Cyanofunctionalization of Vinylarenes

Abstract

In contrast to the rapid growth of synthetic electrochemistry in recent years, enantioselective catalytic methods powered by electricity remain rare. In this work, we report the development of a highly enantioselective method for the electrochemical cyanophosphinoylation of vinylarenes. A new family of serine-derived chiral bisoxazolines with ancillary coordination sites were identified as optimal ligands.

Recent Advances in Asymmetric Catalytic Electrosynthesis

“…The suggested mechanism for the transformation resembles that proposed for the Lin group's preceding work on Cu-catalyzed alkene functionalization in Scheme 11 [77]. The first anodic event leads to the formation of a C-centered radical and the second anodic event produces the active Along the same lines, the Lin group published a second anodically driven enantioselective functionalization of alkenes [78].…”

“…In recent years, asymmetric electrochemical Os-catalyzed dihydroxylation and Mn-catalyzed epoxidation have been demonstrated to work well on a photovoltaic platform for improved process sustainability (Scheme 10) [75,76]. Lin and co-workers described enantioselective cyanophosphinoylation and cyanosulfinylation of alkenes in an anodically driven electrochemical process, using a copper catalyst with a newly developed serine-derived bisoxazoline ligand (Scheme 11) [77]. With a carbon felt anode and Pt cathode in an undivided cell under constant current conditions at 0 °C, a variety of styrene derivatives were functionalized in moderate to good yields with ee's up to 95% (cyanophosphinoylation) and 98% (cyanosulfinylation), including heterocyclic substrates and substrates with functional groups sensitive to oxidation such as aldehyde and sulfide.…”

Catalytic Asymmetric Electrochemical α‐Arylation of Cyclic β‐Ketocarbonyls with Anodic Benzyne Intermediates

“…Though the diastereoselectivity was low in these cases, both diasteroisomers were obtained with high enantioselectivity, indicating the arylation step is under strict catalytic control. The reaction worked well with cyclopentanone and in these cases the chiral primary amine catalyst 3 f was found to give better enantioselectivity (entries [8][9][10][11][12][13][14]. A free ketoamide could also be accommodated to afford the a-arylated adduct 4 ar (33 % yield, 84 % ee, entry 17).…”

“…[5] Anodic oxidation could be employed to in situ generate stabilized electrophilic species such as imine or iminium ion intermediates, in asymmetric aminocatalytic processes, as reported by the groups of Jørgensen [6] and Luo, [7] respectively. Recently, the groups of Meggers, [8] Guo, [9] and Lin [10] have also developed asymmetric catalysis with anodically generated free radical species. Despite these advances, the potential of asymmetric electrochemical catalysis remains largely unexplored.…”

Asymmetric Electrochemical Transformations

“…It has been established that L*Cu(CN) complexes can serve as a latent CN radical in cyanation reactions . Recently, the Lin group developed an enantioselective method for the electrochemical cyanophosphinoylation of styrene (Scheme ) . Several combinations of TMSCN 43 , styrenes 44 , and phosphine oxides 45 were converted to the corresponding products 46 in high yield with excellent enantioselectivity (up to 98 % ee ).…”