New Chiral Lewis Bases Derived from L‐Pipecolinic Acid Showing Stereocontrol Highly Dependent on the Catalyst Design in the Hydrosilylation of N‐Phenyl Ketimines

Abstract

Chiral L-pipecolinic acid based catalysts, the N-functionalized pipecolinamides 4a-h and 5a-e, have been obtained in a straightforward two-step synthesis starting from Boc-Lpipecolinic acid. The catalysts form a complex with trichlorosilane, which proved to be effective for the enantioselective addition to the standard N-phenylimine substrate 6. We have tested the enantioselectivity of the ligands to establish the influence of N-and O-functionalization on the chiral α-amino acid. Whereas the N-formylpipecolinamides give

Catalytic Mechanism Study on the 1,2‐ and 1,4‐Transfer Hydrogenation of Ketimines and β‐Enamino Esters Catalyzed by Axially Chiral Biscarboline‐Based Alcohols

“…[21] Based on the fact that HSiCl 3 reacted completely with primary alcohol like n-butanol to produce hydrogen in 1 h at 0°C in CH 2 Cl 2 , a different mechanism is proposed here (Scheme 2). The strong electron-withdrawing group like F here decreased the enantioselectivity to 91% or 92%.…”

“…The enantioselectivities in 1,2-transfer hydrogenations of fourteen ketimines(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) catalyzed by (aS)-7A. [a] Isolated yields in percentage (%).…”

Mesenteric transection decreases expression of interstitial cells of Cajal in an experimental model

“…Last year the Ibarra group investigated a series of chiral N ‐formyl derivatives of L ‐pipecolinic amides 42. Their catalytic properties in the presence of trichlorosilane were assessed in reductions of the imine obtained from 4′‐(trifluoromethyl)acetophenone and aniline (Scheme ).…”

Trichlorosilane mediated asymmetric reductions of the CN bond

“…29 All were evaluated in the reduction of a single p-trifluoromethylphenyl ketimine, with catalyst 20 providing the best yield and enantioselectivity (Scheme 21). 29 All were evaluated in the reduction of a single p-trifluoromethylphenyl ketimine, with catalyst 20 providing the best yield and enantioselectivity (Scheme 21).…”