611182-62-8Relevant articles and documents
Highly Enantioselective Conjugate Addition of Glycine Imines to Activated Alkenes Catalyzed by Amino-Acid-Derived Chiral Phosphonium Salts
Wen, Shan,Li, Xing,Yao, Weijun,Waheed, Abdul,Ullah, Nisar,Lu, Yixin
, p. 4298 - 4301 (2016/09/13)
Chiral quaternary phosphonium salts derived from amino acids were readily prepared and employed as phase-transfer catalysts for the highly enantioselective conjugate addition of glycine imines to various activated alkenes, including chalcones, acrylates, and vinyl ketones.
Transition state analysis of enantioselective br?nsted base catalysis by chiral cyclopropenimines
Bandar, Jeffrey S.,Sauer, Gregory S.,Wulff, William D.,Lambert, Tristan H.,Vetticatt, Mathew J.
supporting information, p. 10700 - 10707 (2014/08/18)
Experimental 13C kinetic isotope effects have been used to interrogate the rate-limiting step of the Michael addition of glycinate imines to benzyl acrylate catalyzed by a chiral 2,3-bis(dicyclohexylamino) cyclopropenimine catalyst. The reaction is found to proceed via rate-limiting carbon-carbon bond formation. The origins of enantioselectivity and a key noncovalent CH?O interaction responsible for transition state organization are identified on the basis of density functional theory calculations and probed using experimental labeling studies. The resulting high-resolution experimental picture of the enantioselectivity-determining transition state is expected to guide new catalyst design and reaction development.
Enantioselective Bronsted base catalysis with chiral cyclopropenimines
Bandar, Jeffrey S.,Lambert, Tristan H.
supporting information; experimental part, p. 5552 - 5555 (2012/05/20)
Cyclopropenimines are shown to be a highly effective new class of enantioselective Bronsted base catalysts. A chiral 2,3-bis(dialkylamino) cyclopropenimine catalyzes the rapid Michael reaction of a glycine imine substrate with high levels of enantioselectivity. A preparative scale reaction to deliver 25 g of product is demonstrated, and a trivial large scale synthesis of the optimal catalyst is shown. In addition, the basicity of a 2,3-bis(dialkylamino)cyclopropenimine is measured for the first time and shown to be approximately equivalent to the P1-tBu phosphazene base. An X-ray crystal structure of the protonated catalyst is shown along with a proposed mechanistic and stereochemical rationale.
