Ni-Pd Catalyzed Cyclization of Sulfanyl 1,6-Diynes: Synthesis of 1'-Homonucleoside Analogues

Applications of catalytic systems containing DNA nucleobases (adenine, cytosine, guanine, and thymine) in organic reactions

In recent years, nucleobases have attracted special attention because of their abundant resources and multiple interaction sites, which enable them to interact with and functionalize other molecules. This review focuses on the catalytic activities of each of the four main nucleobases found in deoxyribonucleic acid (DNA) in various organic reactions. Based on the studies, most of the nucleobases act as heterogeneous catalytic systems. The authors hope their assessment will help chemists and biochemists to propose new procedures for utilizing nucleobases as catalysts in various organic synthetic transformations. The review covers the corresponding literature published till the end of August 2023.

Synthesis of Cyclic 2-Aminodienes and Aminobenzofulvenes by Rhodium-Catalyzed Hydroaminative Cyclization of Diynes

Regioselective hydroaminative cyclizations of 1,5- and 1,6-diynes via double functionalization of an alkyne carbon were achieved using a phosphine-quinolinolato (PNO) rhodium catalyst. While the reaction of 1,6-diynes with secondary amines provided cyclic 2-aminodienes, phenylene-tethered 1,5-diynes were transformed into benzofulvene derivatives. The reaction is considered to proceed via in situ construction of an aminocarbene ligand, [2 + 2] addition with an internal alkyne moiety, and isomerization to an aminodiene structure. This hydroaminative cyclization proceeds just by heating the substrate with the rhodium catalyst without adding any additive and provides a convenient route to access cyclic 2-aminodiene and aminobenzofulvene derivatives.

Diastereoselective Palladaelectro-Catalyzed Construction of Bromomethyl Morpholines as Key Step To Access Morpholino Homonucleosides

A synthetic protocol for the preparation of a new class of morpholino homonucleosides in enantiopure form starting from readily available 1,2-aminoalcohols or glycidol has been developed. Key intermediates of the synthetic sequence are 2-bromomethyl morpholines, diastereoselectively achieved from the corresponding alkenols by palladaelectro-catalyzed alkoxybromination of unactivated alkenes. The so obtained bromo derivatives are in turn susceptible to functionalization with nucleic bases for easy access to morpholino homonucleosides.

Brønsted Acid-Catalyzed Intramolecular Tandem Double Cyclization of γ-Hydroxy Acetylenic Ketones with Alkynes into Naphtho[1,2-b]furan-3-ones

A metal-free and atom-economic route for the synthesis of naphtho[1,2-b]furan-3-ones has been realized via p-TsOH·H2O-catalyzed intramolecular tandem double cyclization of γ-hydroxy acetylenic ketones with alkynes in formic acid. The benzene-linked furanonyl-ynes are the key intermediates obtained by the scission/recombination of C-O double bonds. Further, the structural modifications of the representative product were implemented by reduction, demethylation, substitution, and [5 + 2]-cycloaddition.

Metal-Free Radical Annulation of Oxygen-Containing 1,7-Enynes: Configuration-Selective Synthesis of (E)-3-((Arylsulfonyl)methyl)-4-Substituted Arylidenechromene Derivatives

A novel strategy for the synthesis of (E)-3-((arylsulfonyl)methyl)-4-substituted benzylidenechromene derivatives via a metal-free radical annulation reaction of oxygen-containing 1,7-enynes with thiosulfonates has been developed. The reaction shows broad substrate scope, wide functional group tolerance, and moderate to excellent yields. Moreover, thiosulfonates were well driven to achieve the bifunctionalization reaction of oxo-1,7-enynes which derived from aliphatic alkynes. In addition, the (E)-configuration of the products was highly controlled by the structure of 1,7-enyne.

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

A unique 1,7-S- and Se-shift reaction under Pummerer reaction conditions of 4-alkenyl-3-sulfinyl- and seleninylpyrroles was described. The usual Pummerer reaction of 4-(alkenylaminomethyl)-3-phenylsulfinylpyrroles and a successive reaction with tetrabutylammonium hydroxide (TBAH) yielded either pyrrolo[3,2-c]azepines or N-pyrrol-3-ylmethyl-N-(4-hydroxy-3-sulfanylpropyl)-p-toluenesulfonamides (diols). Seleno-Pummerer reactions of 3-selanylmethylpyrroles also proceeded via in situ generation of selenoxides, followed by a treatment with TBAH.