An FeCl3-catalyzed Povarov reaction for the efficient synthesis of dibenzo[b,f][1,7]naphthyridines utilizing 1-(2-alkynylaryl)-2-pyrrolecarbaldehydes and arylamines in excellent yields is demonstrated. The essential features of the present strategy are easy preparation of substrates, broad substrate scope, mild reaction conditions, and high atom economy and yields, in the presence of environmentally friendly iron catalysis.
A visible-light-induced multicomponent reaction of vinyl sulfoxonium ylide, thiol, and diazo ester to generate tertiary sulfide is described. The present diastereoselective gem-difunctionalization of the diazo ester can be achieved under mild conditions, as it does not require any additives, catalysts, or transition metals and is tolerant of air and moisture. Due to more nucleophilicity, vinyl sulfoxonium ylide undergoes S–H insertion with thiols to generate an allyl sulfide intermediate. Simultaneously, diazo ester undergoes photolysis to generate a carbene intermediate. Subsequently, the coupling of carbene and allyl sulfide intermediates generates sulfonium ylide, which undergoes Doyle–Kirmse rearrangement to generate tertiary sulfide scaffolds.
Iodine-mediated oxidative annulations of N-benzyl-propiolamides are disclosed for the first time, providing either azaspiro[5.5]undecatrienones via dearomative ipso-annulation or benzo[c]azepinones through ortho-annulation. The selective construction of the aforementioned products is based on the ceric ammonium nitrate (CAN)-promoted divergent reactivity of the propiolamide, directed by the substituents on the phenyl ring of the N-benzyl group.
Using a reagent- and catalyst-free approach, a series of 2-substituted 1,2,3,4-tetrahydroquinazolines is synthesized by cyclocondensation between aldehydes and 2-aminobenzylamines via dehydration in water. The reactions are complete in 2 minutes under microwave irradiation and proceed well under stirring at room temperature, affording tetrahydroquinazolines in high to excellent yields. The products are water-insoluble and are isolated by simple filtration, avoiding a conventional work-up step and offering an organic-solvent-free process. Furthermore, the tetrahydroquinazolines are efficiently oxidized in a micellar medium derived from cetyltrimethylammonium bromide (CTAB) using a cheap commercial bleaching solution (4% NaOCl in water) to give quinazolines in high yields. This sustainable protocol has a near zero E-factor.
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