Concomitant C(.alpha.),C(.beta.)-asymmetric induction in the aza-Claisen rearrangement of N-allylketene N,O-acetals

Electrophilic rearrangements of chiral amides: a traceless asymmetric α-allylation

A one-pot protocol for the asymmetric α-allylation reaction is reported relying on a key efficient asymmetric Claisen rearrangement, triggered by electrophilic activation of chiral pseudoephedrine amides. Subsequent reduction or hydrolysis of the resulting iminium ions provides highly enantioenriched α-allylic aldehydes or carboxylic acids in a traceless manner. Compared to traditional alternatives which make use of strongly basic conditions, the work presented herein displays unprecedented functional group tolerance.

Intercepting the Breslow intermediate via Claisen rearrangement: synthesis of complex tertiary alcohols without organometallic reagents

A novel Claisen rearrangement in which the Breslow intermediate is engaged as a hydroxy-substituted N,S-ketene acetal to provide complex 3° alcohols without the use of organometallic reagents is reported. The reaction constitutes an unprecedented reactivity mode for the Breslow intermediate.

Computational studies on 3-aza-Cope rearrangements: protonation-induced switch of mechanism in the reaction of vinylpropargylamine

The 3-aza-Cope rearrangements of 3-azoniahexa-1,5-diene (1), 3-azoniahex-1-ene-5-yne (3), and 3-azahex-1-ene-5-yne (5) were investigated up to the coupled-cluster level, CCSD(T), by using a valence triple-zeta basis set. Activation barriers and geometrical parameters of the transition states are provided. Conformational studies were performed for all reactants and products of the reactions. Solvent effects were estimated from self-consistent reaction field calculations. In contrast to the other two species, the Cope rearrangement of 5 was found to proceed by a stepwise mechanism.