作者:Lee Belding、Matt Guest、Richard Le Sueur、Travis Dudding
DOI:10.1021/acs.joc.8b00770
日期:2018.6.15
derivatives. Associated with this structural reorganization was an inward gearing of the cyclopropenium ring and twisting of the peri-NMe2 group into coplanarity with the naphthalene ring system. Further, reinforcement of an intramolecular H-bond (IMHB) in the excited state of these derivatives alludes to the importance of photoinduced H-bonding in this new class of cyclopropenium based fluorophores
Enantioselective Brønsted Base Catalysis with Chiral Cyclopropenimines
作者:Jeffrey S. Bandar、Tristan H. Lambert
DOI:10.1021/ja3015764
日期:2012.3.28
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 P-1-tBu phosphazene base. An X-ray crystal structure of the protonated catalyst is shown along with a proposed mechanistic and stereochemical rationale.