Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck-Matsuda desymmetrization of -protected 2,5-dihydro-1-pyrroles.

We report herein an enantioselective palladium-catalyzed Heck-Matsuda reaction for the desymmetrization of -protected 2,5-dihydro-1-pyrroles with aryldiazonium salts, using the chiral ,-ligand ()-PyraBox. This strategy has allowed straightforward access to a diversity of 4-aryl-γ-lactams via Heck arylation followed by a sequential Jones oxidation. The overall method displays a broad scope and good enantioselectivity, favoring the () enantiomer.

Secondary-sphere modification in proline catalysis: old friend, new connection.

In this work, we exploit our strategy of secondary-sphere modification of organocatalysts to improve the reactivity and selectivity of amino catalysts. Herein, the carboxylic acid moiety of proline was targeted as a site for modification under catalytic reaction conditions with boronic acids. Intermolecular aldol reactions between aromatic aldehydes and cyclopentanone were selected as a proof-of-concept because cyclopentanone as an aldol donor was often associated with decreased selectivity compared to its 6-membered ring analog, hexanone.

Effect of Solvents on Proline Modified at the Secondary Sphere: A Multivariate Exploration.

The critical influence of solvent effects on proline-catalyzed aldol reactions has been extensively described. Herein, we apply multivariate regression strategies to probe the influence of different solvents on an aldol reaction catalyzed by proline modified at its secondary sphere with boronic acids. In this system, both binding of the boronic acid to proline and the outcome of the aldol reaction are impacted by the solvent-controlled microenvironment.

Experimental and theoretical studies on gold(III) carbonyl complexes: reductive C,H- and C,C bond formation.

The reactivity of cationic (C^C)gold(iii) carbonyl complexes was investigated. While the in situ-formed IPrAu(bph)CO+ complex (bph = biphenyl-2,2'-diyl) does not undergo a migratory insertion of CO into the neighboring gold-carbon bond, nucleophiles can attack the coordinated CO moiety intermolecularly. Water as a nucleophile initiates a CO2 extrusion combined with a reductive C,H bond formation.

A General Organocatalytic System for Enantioselective Radical Conjugate Additions to Enals.

Herein, we report a general iminium ion-based catalytic method for the enantioselective conjugate addition of carbon-centered radicals to aliphatic and aromatic enals. The process uses an organic photoredox catalyst, which absorbs blue light to generate radicals from stable precursors, in combination with a chiral amine catalyst, which secures a consistently high level of stereoselectivity. The generality of this catalytic platform is demonstrated by the stereoselective interception of a wide variety of radicals, including non-stabilized primary ones which are generally difficult to engage in asymmetric processes.

Synthesis of Fulvene Vinyl Ethers by Gold Catalysis.

Gold-catalyzed cyclization of 1,5-diynes with ketones as reagents and solvent provides diversely substituted vinyl ethers under mild conditions. The regioselectivity of such gold-catalyzed cyclizations is usually controlled by the scaffold of the diyne. Herein, we report the first solvent-controlled switching of regioselectivity from a 6-endo-dig- to 5-endo-dig-cyclization in these transformations, providing fulvene derivatives.

Different Selectivities in the Insertions into C(sp )-H Bonds: Benzofulvenes by Dual Gold Catalysis Competition Experiments.

An unprecedented, often almost quantitative access to tricyclic aromatic compounds by dual gold catalysis was developed. This synthetic route expands the scope of benzofulvene derivatives through a C(sp )-H bond insertion in easily available starting materials. The insertion takes place with an exclusive chemoselectivity with respect to the competing aromatic C-H positions.