Asymmetric organocatalytic anthrone additions to activated alkenes

Copper-Catalyzed Remote Asymmetric Yne-Allylic Substitution of Yne-Allylic Esters with Anthrones

Anthrones are key structural motifs in many natural products and pharmaceutical chemicals. However, due to its unique tricyclic aromatic structure, the synthetic space for the development of chiral anthrone derivatives is largely limited. By utilizing the potential of the copper-catalyzed remote asymmetric yne-allylic substitution reaction, we describe the first example of copper-catalyzed highly regio- and enantioselective remote yne-allylic substitution on various yne-allylic esters with anthrones under a mild reaction condition, which afforded a range of enantioenriched 1,3-enynes with exhibiting broad functional group tolerance across 51 examples.

Straightforward Access to Anthrone Functionalized Benzylic Amines via Organocatalytic 1,2-Addition of Anthrones to Imines at Ambient Temperature

Activation of anthrone via benzylic deprotonation in the presence of triethylamine paves the way for the 1,2-addition reaction with imines to provide the desired functionalized anthrones in good to excellent yields under mild and operationally simple reaction conditions with a broad range of substrate scopes without using any external additives or toxic stoichiometric reagents.

Effective asymmetric Michael addition of anthrone to nitroalkenes using chiral tetraoxacalix[2]arene[2]triazines as organocatalysts

Novel chiral secondary amines bearing a tetraoxacalix[2]arene[2]triazine scaffold were created and used for catalytic asymmetric Michael reaction of anthrone with nitroalkenes. The relevant adducts were obtained in good to excellent yields (82%-98%) and enantioselectivities (75%-98%).

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

Starting from (S)-β-phenylalanine, easily accessible by lipase-catalyzed kinetic resolution, a chiral triamine was assembled by a reductive amination and finally cyclized to form the title compound 10. In the crystals of the guanidinium benzoate salt the six membered rings of 10 adopt conformations close to an envelope with the phenyl substituents in pseudo-axial positions. The unprotonated guanidine 10 catalyzes Diels–Alder reactions of anthrones and maleimides (25–30% ee). It also promotes as a strong Brønsted base the retro-aldol reaction of some cycloadducts with kinetic resolution of the enantiomers. In three cases, the retro-aldol products (48–83% ee) could be recrystallized to high enantiopurity (≥95% ee). The absolute configuration of several compounds is supported by anomalous X-ray diffraction and by chemical correlation.

L-Proline Derived Bifunctional Organocatalysts: Enantioselective Michael Addition of Dithiomalonates to trans-β-Nitroolefins

A series of novel L-proline derived tertiary amine bifunctional organocatalysts 9 are reported, which were applied to the asymmetric Michael addition of dithiomalonates 2 to trans-β-nitroolefins 1. The reaction proceeded in high yields (up to 99%) with high enantioselectivities (up to 97% ee). The synthetic utility of this methodology was demonstrated in the short synthesis of (R)-phenibut in high yield.

Expanding the scope of Metal-Free enantioselective allylic substitutions: Anthrones

The highly enantioselective asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with anthrones is presented. The reaction is simply catalyzed by cinchona alkaloid derivatives affording the final alkylated products in good yields and excellent enantioselectivities.

Benzylic Functionalization of Anthrones via the Asymmetric Ring Opening of Oxabicycles Utilizing a Fourth-Generation Rhodium Catalytic System

While anthrones exist as privileged scaffolds in bioactive molecules, the enantioselective functionalization of anthrones is surprisingly scarce in the literature, with no asymmetric transition metal catalyzed example to date. Herein, we report the first asymmetric transition metal catalyzed benzylic functionalization of anthrones through the rhodium(I) catalyzed desymmetrization of oxabicycles. As previously developed rhodium(I) systems were found to be unsuitable for this substrate, a new robust fourth-generation [Rh(cod)OH]2 based catalytic system was developed to address synthetic challenges in this protocol.