Enantioselective Aza-Morita-Baylis-Hillman Reactions of Acrylonitrile Catalyzed by Palladium(II) Pincer Complexes havingC2-Symmetric Chiral Bis(imidazoline) Ligands

Synthesis of Diastereoenriched α-Aminomethyl Enaminones via a Brønsted Acid-Catalyzed Asymmetric aza-Baylis-Hillman Reaction of Chiral N-Phosphonyl Imines

An effective chiral GAP methodology for preparing α-aminomethyl enaminones through a (R)-CSA-catalyzed asymmetric aza-Baylis-Hillman reaction is reported. Excellent yields and high diastereoselectivity could be obtained under mild conditions and convenient GAP techniques. The confirmations of the absolute configuration of N-phosphonyl imine and chiral enaminone by X-ray diffraction provides an explicit explanation of the chirality mechanism for GAP chemistry.

Dual Palladium(II)/Tertiary Amine Catalysis for Asymmetric Regioselective Rearrangements of Allylic Carbamates

The streamlined catalytic access to enantiopure allylic amines as valuable precursors towards chiral β- and γ-aminoalcohols as well as α- and β-aminoacids is desirable for industrial purposes. In this article an enantioselective method is described that transforms achiral allylic alcohols and N-tosylisocyanate in a single step into highly enantioenriched N-tosyl protected allylic amines via an allylic carbamate intermediate. The latter is likely to undergo a cyclisation-induced [3,3]-rearrangement catalysed by a planar chiral pentaphenylferrocene palladacycle in cooperation with a tertiary amine base. The otherwise often indispensable activation of palladacycle catalysts by a silver salt is not required in the present case and there is also no need for an inert gas atmosphere. To further improve the synthetic value, the rearrangement was used to form dimethylaminosulfonyl-protected allylic amines, which can be deprotected under non-reductive conditions.

Asymmetric aza-Morita–Baylis–Hillman reactions of chiral N-phosphonyl imines with acrylates via GAP chemistry/technology

A series of aza-Morita–Baylis–Hillman acrylates have been synthesized by using chiral N-phosphonyl imines and GAP chemistry/technology.

Enantioselective synthesis and application to the allylic imidate rearrangement of amine-coordinated palladacycle catalysts of cobalt sandwich complexes

The reaction of (η(5)-(N,N-dimethylaminomethyl)cyclopentadien-yl)(η(4)-tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)-N-acetylphenylalanine gave planar chiral palladacycle di-μ-chloridebis[(η(5)-(Sp)-2-(N,N-dimethylaminomethyl)cyclopentadienyl,1-C,3'-N)(η(4)-tetraphenylcyclobutadiene)cobalt]dipalladium [(Sp )-Me2 -CAP-Cl] in 92% ee and 64% yield. Enantiopurity (>98% ee) was achieved by purification of the monomeric (R)-proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (Sp)-Me2-CAP-OAc which was applied to asymmetric transcyclopalladation (up to 78% ee). The (R)-N-acetylphenylalanine mediated palladation methodology was applicable also to the corresponding N,N-diethyl (82% ee, 39% yield) and pyrrolidinyl (>98% ee, 43% yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(Sp)-Pyrr-CAP-Cl] and AgNO3 (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (E)-N-aryltrifluoroacetimidate (up to 83% ee), and this catalyst system is also applicable to the rearrangement of a range of (E)-trichloroacetimidates (up to 99% ee). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non-racemic allylic amine derivatives.