Access to P-Stereogenic Phosphinates via N-Heterocyclic Carbene-Catalyzed Desymmetrization of Bisphenols
作者:Zhijian Huang、Xuan Huang、Baosheng Li、Chengli Mou、Song Yang、Bao-An Song、Yonggui Robin Chi
DOI:10.1021/jacs.6b04624
日期:2016.6.22
remote P-stereogenic centers is disclosed. The catalytic reactions can be performed on gram scales with 1 mol % N-heterocycliccarbene (NHC) catalyst, providing efficient access to enantiomerically enriched P-stereogenic phosphinates. The chiral phosphinates prepared with our method can find widespread applications as asymmetric organic catalysts and ligands.
Two new chiral diphenylphosphine dioxides bearing an original bis(triazolyl) backbone were prepared through a two‐step sequence. The key reactioninvolves a copper‐catalyzed [3+2] cycloaddition/dimerization reaction leading to the formation of five bonds in one chemical step with 100 % atom efficiency. Interestingly, these ligands exhibited good to excellent catalytic activities as chiral Lewis base
transformations using chlorosilane reagents. The p-tolyl-substituted DIOPO (p-tolyl-DIOPO) was most effective for the reductive aldol reaction of chalcone and aldehydes with trichlorosilane, whereas the 2,8-dimethylphenoxaphosphine-derived DIOPO (DMPP-DIOPO) afforded the best enantioselectivity for the phosphonylation of conjugated aldehydes and the chlorinative aldol reaction of an ynone and benzaldehyde.
Chiral Lewis base organocatalysts activate trichlorosilane to promote the tandem conjugate reduction/aldol reaction of α,β‐unsaturated ketones with aldehydes to give optically active β‐hydroxy ketones with good to high syn diastereo‐ and enantioselectivities. The reaction tolerates α,β‐unsaturated aldehydes owing to the chemoselective conjugate reduction of enones in the presence of enals.