Three‐component reactions involving 3‐amino‐1,2,4‐triazole, aldehydes, including salicylic aldehydes, and pyruvic acids were studied in detail. The reaction pathway and products of the heterocyclizations could be changed by variation of the reaction parameters. The broad antimicrobial activity of the products was also studied. Compound 9d showed specific anti‐influenza virus (A/H1N1) activity, with an IC50 of 0.57 μM and a CC50 of >100 μM.

Abstract:We report herein the use of ad ual catalytic system comprising aL ewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine and ap hotoredox catalyst to generate carbon radicals from either boronic acids or esters.T his system enabled awide range of alkylboronic esters and aryl or alkylb oronic acids to react with electron-deficient olefins via radical addition to efficiently form C À Cc oupled products in aredox-neutral fashion. The Lewis base catalyst was shown to form ar edox-active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.Carbon-centered radicals are as ynthetically powerful class of reactive intermediates.[1] They are particularly attractive in the context of C À Cb ond-forming reactions, [2] overcoming problems often associated with two-electron processes.[3] By enabling visible-light-promoted single electron transfer, photoredox catalysis has become am ethod of choice for the single-electron reduction or oxidation of organic substrates and allows to generate open-shell intermediates in amild and selective fashion.[4] Ar ange of reductive or oxidative carbon radical precursors are now available to generate carbon radicals in the context of ap hotocatalytic cycle.[5] Oxidative carbon radical precursors are often anionic species suffering from poor solubility in common organic solvents.F or example,e xtensively studied organoborates [6] possess an electron-rich B(sp 3 )m oiety that can be subjected to singleelectron oxidation, leading to an eutral carbon radical after CÀBbond cleavage (Scheme 1A).Despite their ubiquity as reagents in organic synthesis [7] and in biologically active molecules, [8] theuse of boronic acid derivatives to generate carbon-centered radicals remains underexplored.[9] Owing to their high oxidation potentials, they have received much less attention in this regard, with few reports making use of strong stoichiometric oxidants or anodic oxidation.[10] We recently demonstrated that benzyl boronic esters can undergo single-electron oxidation under photoredox conditions when their vacant porbital is engaged in ad ative bond with the norbital of as toichiometric Lewis base (LB) additive (Scheme 1B).[11] Lewis base catalysis was introduced as aconcept by Denmark to enhance the reactivity of electrophilic n*, p*, and s*orbitals.[12] Based on this knowledge,w eh ypothesized that the use of ac atalytic amount of an organic Lewis base would be av iable option for the photoredox activation of boronic acids and esters. [13] Herein, we describe adual catalytic method to effectively form alkyl and aryl radicals from aw ide array of boronic esters and acids by direct photoredox single-electron oxidation under mild and safe conditions,without the requirement for stoichiometric activators or oxidants.T hese reactive species were further engaged in intermolecular C À Cb ondforming processes to deliver desirable C(sp 3 )ÀC(sp 3 )a nd C(sp 2 )ÀC(sp 3 )bonds in ar edox-neutral fashion. Thea ddition of electron-rich carbon...

We report the utilization of a novel catalyst for cycloisomerizations. The novel catalyst system contains gold nanoparticles supported on Al-SBA15, which was prepared by the ball-milling process. We developed a greener methodology for synthesizing spiroindolines under heterogeneous conditions, using this novel class of supported gold nanoparticles in combination with microwave irradiation. The catalyst is highly reusable and selective. Cycloisomerization reaction yields ranged from good to excellent leading to the formation of two novel classes of six- and seven-membered heterocycles, which have been unprecedented so far. The selectivity of the catalyst towards the desired products is high and the reaction can be performed in ethanol as the solvent. A one-pot cascade reaction could be established commencing with the Ugi-reaction to ensure diversity

No abstract