Regioselective reductions of β,β-disubstituted enones catalyzed by nonracemically ligated copper hydride

Catalytic Asymmetric Synthesis of Allylic Alcohols and Derivatives and their Applications in Organic Synthesis

“…[271] Allylic alcohols were isolated with moderate to excellent enantiomeric excess and good 1,2-regioselectivity (ratio 258 a/258 b). [271] Allylic alcohols were isolated with moderate to excellent enantiomeric excess and good 1,2-regioselectivity (ratio 258 a/258 b).…”

Zinc‐Catalyzed Enantioselective Hydrosilylation of Ketones and Imines under Solvent‐Free Conditions

“…However, the reaction deserves special attention, as so‐obtained allyl alcohols and amines may be used for a wide range of subsequent diastereoselective transformations . Recently, Lipshutz provided protocols for the CuH‐catalyzed 1,2‐reduction of β,β‐ and α‐substituted enones leading to secondary allyl alcohols (Scheme c) ,. High enantioselectivities (up to 95 %) were induced by expensive and difficult to obtain 4,4′‐bi‐1,3‐benzodioxole‐5,5′‐diylbis(diphenylphosphine) (SEGPHOS) and biphenylphosphine (BIPHEP) ligands.…”

(R)- and (S)-2,2′-Bis(diphenylphosphino)-6,6′-dimethoxy-1,1′-biphenyl

“…(97) In a subsequent study, the choice of ligand was revealed to be crucial in achieving regioselectivity in a 1,4-or 1,2-sense for the catalytic asymmetric reduction of acyclic β,β-disubstituted enones with copper hydride (eq 98). 125 Ferrocene-type ligands such as JOSIPHOS led to high 1,4-selectivity, whereas biaryl phosphines such as BIPHEP and SEGPHOS gave predominantly 1,2-addition. The apparent discriminating factor of the ligand to determine the regioselectivity in these reductions is the ability to stabilize either S-cis or S-trans conformations of the enone.…”