An Efficient Carbene-Catalyzed Access to 3,4-Dihydrocoumarins
摘要:
Dihydrocoumarins play an important role as flavor and fragrance compounds and can be prepared efficiently from o-hydroxycinnamaldehydes in a mild, atom-economic N-heterocyclic carbene-catalyzed redox lactonization. Corresponding coumarins are accessible via a one-pot domino oxidation lactonization procedure in the presence of oxidants.
Intramolecular Stereoselective Protonation of Aldehyde-Derived Enolates
作者:Anastasie Kena Diba、Claudia Noll、Michael Richter、Marc Timo Gieseler、Markus Kalesse
DOI:10.1002/anie.201004619
日期:2010.11.2
Picking sides: Asymmetric protonation of the titled compounds poses a most significant challenge and has been addressed by taking advantage of internal protonation and subsequent hemiacetal formation to avoid epimerization (see scheme). The substrates employed in these transformations can be easily accessed through a sequence of vinylogous aldol reactions with subsequent conjugate reductions.