Recent advances in the Overman rearrangement: synthesis of natural products and valuable compounds

This review documents the reports since 2005 on the Overman rearrangement, an important C–N bond forming reaction that has been profoundly used in the synthesis of natural products, synthetic intermediates, building blocks and valuable compounds.

Heteromultimetallic catalysis for sustainable organic syntheses

Fully complementary bimetallic catalysis has been identified as an increasingly powerful tool for molecular transformations, which was largely inspired by early examples of sequential catalytic transformations.

Asymmetric synthesis of cis-aminocyclopentenols, building blocks for medicinal chemistry

A highly efficient one-pot multistep process involving an asymmetric Pd(II)-catalyzed Overman rearrangement and a Ru(II)-catalyzed ring-closing metathesis reaction has been developed for the preparation of (R)- or (S)-aminocyclopenta-2-enes. The rapid strategy employed and the relatively mild conditions of the one-pot process allowed the multigram synthesis of the carbocycles in high enantiomeric excess (92% ee). The synthetic utility of these compounds was demonstrated by the stereoselective incorporation of hydroxyl groups, generating cis-4- and cis-5-aminocyclopenta-2-en-1-ols, important building blocks for medicinal chemistry.

Preparation of amino-substituted indenes and 1,4-dihydronaphthalenes using a one-pot multireaction approach: total synthesis of oxybenzo[c]phenanthridine alkaloids

Allylic trichloroacetimidates bearing a 2-vinyl or 2-allylaryl group have been designed as substrates for a one-pot, two-step multi-bond-forming process leading to the general preparation of aminoindenes and amino-substituted 1,4-dihydronaphthalenes. The synthetic utility of the privileged structures formed from this one-pot process was demonstrated with the total synthesis of four oxybenzo[c]phenanthridine alkaloids, oxychelerythrine, oxysanguinarine, oxynitidine, and oxyavicine. An intramolecular biaryl Heck coupling reaction, catalyzed using the Hermann-Beller palladacycle was used to effect the key step during the synthesis of the natural products.

Toward a symphony of reactivity: cascades involving catalysis and sigmatropic rearrangements

Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder. It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.

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.