Copper‐Catalyzed Asymmetric 1,4‐Hydroboration of Coumarins with Pinacolborane: Asymmetric Synthesis of Dihydrocoumarins
作者:Hyohyun Kim、Jaesook Yun
DOI:10.1002/adsc.201000310
日期:2010.10.9
An efficient asymmetric addition of pinacolborane to 4-substituted coumarins proceeded with high enantioselectivity in the presence of a copper(I)-QuinoxP complex as a catalyst to produce the corresponding 1,4-hydroboration products. Treatment of the intermediates with electrophiles, without isolation, resulted in enantioenriched dihydrocoumarins. The utility of this protocol was demonstrated in the
Catalytic Asymmetric Addition of Meldrum’s Acid, Malononitrile, and 1,3-Dicarbonyls to<i>ortho</i>-Quinone Methides Generated In Situ Under Basic Conditions
unstable ortho‐quinone methides (o‐QMs) in catalyticasymmetric settings is presented. The enantioselective reactions are catalysed by bifunctional organocatalysts, and the o‐QM intermediates are formed in situ from 2‐sulfonylalkyl phenols through base‐promoted elimination of sulfinic acid. The use of mild Brønsted basicconditions for transiently generating o‐QMs in catalyticasymmetric processes is unprecedented
Asymmetric Conjugate Reductions of Coumarins. A New Route to Tolterodine and Related Coumarin Derivatives
作者:Brian D. Gallagher、Benjamin R. Taft、Bruce H. Lipshutz
DOI:10.1021/ol9020404
日期:2009.12.3
The combination of catalytic amounts of [(R)-DTBM-SEGPHOS]CuH in the presence of stoichiometric DEMS (diethoxymethylsilane) in toluene at room temperature leads to asymmetric reductions of 4-substituted coumarins. Several targets or their known precursors can be prepared in high yields and ee’s, including the muscarine receptor antagonist (R)-tolterodine.