Visible Light Promoted [3+2]-Cycloaddition for the Synthesis of Cyclopenta[b]chromenocarbonitrile Derivatives.

In the manuscript, a novel method for the preparation of cyclopenta[b]chromenocarbonitrile derivatives via [3+2] cycloaddition reaction of substituted 3-cyanochromones and N-cyclopropyloamines initiated by visible light catalysis has been described. The reaction was performed in the presence of Eosin Y as a photocatalyst. The key parameters responsible for the success of the described strategy are visible light, a small amount of photoredox catalyst, an anhydrous solvent, and an inert atmosphere.

Enantioselective, Decarboxylative (3+2)-Cycloaddition of Azomethine Ylides and Chromone-3-Carboxylic Acids.

Herein, we describe the synthesis of a variety of chiral hybrid pyrrolidine-chromanone polycyclic derivatives. A convenient (3+2)-annulation of azomethine ylides with chromone-3-carboxylic acid realized under Brønsted base catalysis produced highly functionalized products in high yields with good stereoselectivities through asymmetric, intermolecular, and decarboxylative (3+2)-cyclization.

Visible Light-Driven Reductive Azaarylation of Coumarin-3-carboxylic Acids.

In the manuscript, reductive and decarboxylative azaarylation of coumarin-3-carboxylic acids is described. It utilizes the photocatalytic activation of (cyano)azaarenes in the presence of fac-Ir(ppy)3 as a photocatalyst. The methodology is versatile and provides access to biologically relevant 4-substituted-chroman-2-ones. Visible light, photoredox catalyst, base, anhydrous solvent, and inert atmosphere constitute key parameters for the success of the described strategy. The developed methodology involves a wide range of coumarin-3-carboxylic acids as well as (cyano)azaarenes.

Visible-light synthesis of 4-substituted-chroman-2-ones and 2-substituted-chroman-4-ones via doubly decarboxylative Giese reaction.

Doubly decarboxylative, photoredox synthesis of 4-substituted-chroman-2-ones and 2-substituted-chroman-4-ones is described. The reaction involves two independent decarboxylation processes: the first one initiating the cycle and the second completing the process. Visible light, photoredox catalyst, base, anhydrous solvent and inert atmosphere constitute the key parameters for the success of the developed transformation. The protocol proved applicable for coumarin-3-carboxylic acids and chromone-3-carboxylic acids as well as N-(acyloxy)phthalimide which served as precursors of the corresponding alkyl radicals.

Synthesis of unsymmetrical alkyl acetals via addition of primary alcohols to allyl ethers mediated by ruthenium complexes.

ABSTRACT: Ru-catalyzed synthesis of mixed alkyl-alkyl acetals via addition of primary alcohols to allyl ethers has been extended to include long-chain and/or functionalized substrates. The catalytic systems for these reactions were generated from RuCl2(PPh3)3 and [RuCl2(1,5-COD)]x and phosphines [PPh3 or P(p-chlorophenyl)3] or SbPh3. Of particular importance is the almost quantitative elimination of transacetalization. The addition proceeds through allyl complexes, not via isomerization of allyl ethers--subsequent addition of ROH to vinyl ethers.