Catalytic Asymmetric Protonation of Silyl Ketene Imines
摘要:
An efficient catalytic and highly enantioselective protonation of silyl ketene imines is described. The reaction is catalyzed by the chiral phosphoric acids TRIP or STRIP in the presence of a stoichiometric amount of methanol as the proton source and silyl acceptor. A variety of substituted racemic silyl ketene imines have been transformed into highly enantioenriched nitriles.
Enantioselective Construction of Quaternary Stereogenic Carbon Atoms by the Lewis Base Catalyzed Additions of Silyl Ketene Imines to Aldehydes
作者:Scott E. Denmark、Tyler W. Wilson、Matthew T. Burk
DOI:10.1002/chem.201403342
日期:2014.7.21
the aldol addition reaction. In the presence of SiCl4 and the catalytic action of a chiral phosphoramide, silyl ketene imines undergo extremely rapid and high yielding addition to a wide variety of aromatic aldehydes with excellent diastereo‐ and enantioselectivity. Of particular note are the high yields and selectivities obtained from electron‐rich, electron‐poor, and hindered aldehydes. Linear aliphatic
Herein, a coupling reaction of enol ethers with silyl ketene imines in the presence of catalytic amounts of InBr3 and Me3SiBr is described. Kinetic studies have revealed that an indium catalyst and Me3SiBr accelerated the coupling process and the regeneration of the catalyst, respectively. Various types of enol ethers and silyl ketene imines are applicable. In addition, a formal synthesis of verapamil
A highly enantioselective Mannich reaction of silyl ketene imines with isatin‐derived ketimines has been realized by using a chiral N,N′‐dioxide/ZnII catalyst. A variety of β‐amino nitriles containing congested vicinal tetrasubstituted stereocenters were obtained with excellent outcomes (up to 98 % yield, >19:1 d.r. and 99 % ee). Based on the experimental investigations, a possible transition state
containing contiguous tertiary and quaternary stereogenic carbon centers were synthesized by using the title reaction. The reaction was catalyzed by a chiral N,N′‐dioxide scandium(III) complex under mild reaction conditions. Based on experimental investigations, a possible transition state has been proposed to explain the origin of asymmetric inductivity.