Stereoselective reaction of 2-carboxythioesters-1,3-dithiane with nitroalkenes: an organocatalytic strategy for the asymmetric addition of a glyoxylate anion equivalent
Organocatalytic asymmetric α-benzoyloxylation of α-branched aldehydes and enals: a useful approach to oxygenated quaternary stereocenters
摘要:
Direct asymmetric alpha-benzoyloxylation of alpha-branched aldehydes and alpha-branched enals via enamine and dienamine catalysis was used to construct quaternary oxygenated stereocenters with good yields and moderate to good enantioselectivity. This method uses an inexpensive and readily available cinchona alkaloid-derived primary amine as the catalyst, benzoyl peroxide as the oxygen source, and stoichiometric amounts of the aldehyde substrates, providing simple metal-free access to valuable protected 2-hydroxyaldehyde derivatives. (C) 2012 Published by Elsevier Ltd.
9‐amino‐9‐deoxy‐epi‐quinine were then used in the same reaction with different substrates, leading to the desired products in high yield and ee, as well as in three other reactions operating with different mechanism. An investigation of the recyclability of the polystyrene‐ and poly(ethylene glycol)‐supported systems showed that these could be recovered and recycled with no loss of stereochemical activity but with a
A chiral mesoporous organosilica material incorporating a urea based-cinchona derivative and propylamine groups was prepared by a co-condensation method. The multisite solid catalyst efficiently promoted the asymmetric multicomponent reaction of aldehydes, malonates and nitromethane.
The present invention provides a process for preparing a substantially stereochemically pure compound of formula (I), or a salt thereof wherein R1 and R2 are independently selected from the group consisting of H, -CH2-CH3, and -CH=CH2, the process comprising the step of demethylating the corresponding methylated compound of formula (II) in the presence of an alkaline or alkaline earth metal (C1-C10) alkylthiolate salt and a polar aprotic solvent.
New cinchona‐based primary amine catalysts were prepared and screened as organocatalysts for the γ‐alkylation of α,β‐unsaturated aldehydes with bis(4‐dimethylaminophenyl)methanol. Catalyst C3 containing acetic acid group yielded γ‐alkylated products with good enatioselectivities.