The MARDi Cascade: A Michael-Initiated Domino-Multicomponent Approach for the Stereoselective Synthesis of Seven-Membered Rings

Direct Access to Highly Enantioenriched α-Branched Acrylonitriles through a One-Pot Sequential Asymmetric Michael Addition/Retro-Dieckmann/Retro-Michael Fragmentation Cascade

A highly enantioselective synthesis of α-branched acrylonitriles is reported featuring a one-pot sequential asymmetric Michael addition/retro-Dieckmann/retro-Michael fragmentation cascade. The method, which relies on a solid, bench-stable, and commercially available acrylonitrile surrogate, is practical, scalable, and highly versatile and provides a direct access to a wide range of enantioenriched nitrile-containing building blocks. Most importantly, the method offers a new tool to incorporate an acrylonitrile moiety in an asymmetric fashion.

A switchable dual organocatalytic system and the enantioselective total synthesis of the quadrane sesquiterpene suberosanone

Switch it! The combination of aminocatalysis and N-heterocyclic carbene catalysis has been extended to a switchable dual catalytic system.

Base catalyzed synthesis of bicyclo[3.2.1]octane scaffolds

A base-catalyzed and time controlled reaction of 1,3-cyclopentanediones tethered to activated olefins afforded in high yields either bicyclo[3.2.1]octane-6,8-dione or bicyclo[3.2.1]octane-6-carboxylate derivatives.

Recent developments in asymmetric multicomponent reactions

Multicomponent reactions (MCRs) receive increasing attention because they address both diversity and complexity in organic synthesis. Thus, in principle diverse sets of relatively complex structures can be generated from simple starting materials in a single reaction step. The ever increasing need for optically pure compounds for pharmaceutical and agricultural applications as well as for catalysis promotes the development of asymmetric multicomponent reactions. In recent years, asymmetric multicomponent reactions have been applied to the total synthesis of various enantiopure natural products and commercial drugs, reducing the number of required reaction steps significantly. Although many developments in diastereoselective MCRs have been reported, the field of catalytic enantioselective MCRs has just started to blossom. This critical review describes developments in both diastereoselective and catalytic enantioselective multicomponent reactions since 2004. Significantly broadened scopes, new techniques, more environmentally benign methods and entirely novel MCRs reflect the increasingly inventive paths that synthetic chemist follow in this field. Until recently, enantioselective transition metal-catalyzed MCRs represented the majority of catalytic enantioselective MCRs. However, metal contamination is highly undesirable for drug synthesis. The emergence of organocatalysis greatly influences the quest for new asymmetric MCRs.

A one-pot sequence for the efficient synthesis of highly functionalized macrocarbocycles or bridged 2,8-dioxabicyclo[3.2.1]octanes from 1-nitrobicyclic compounds

The reaction of 1-nitrobicyclo[n.3.1]alkane-(6 + n)ones with sodium borohydride followed by acidic workup led to ring opening via a one-pot sequence comprising the retro-Dieckmann-type opening of the α-nitroketone structural fragment, followed by aldehyde reduction and a final Nef reaction, leading to highly functionalized 12 to 14-membered carbocyclic ketones bearing three stereocenters, which are adjacent in some of the compounds. The reactions starting from 1-nitrobicyclo[9.3.1]pentadecan-15-ones could be adjusted to give macrocyclic 2,8-dioxabicyclo[3.2.1]octanes containing an additional bridge by diastereoselective formation of a third ring and a fourth stereocenter through acid-promoted intramolecular ketal formation. This is a very interesting ring system related to the core of the zaragozic acid family of natural products.