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Regioselective addition of 1,3‐dicarbonyl compounds to N‐alkynyl‐3‐hydroxyisoindolin‐1‐ones (α‐hydroxy ynamides) was accomplished with the use of NiII salt catalysts. The reaction proceeded by a tandem decyclization–addition–cyclization mechanism, in which a ketenimine intermediate is formed via NiII‐catalyzed isomerization of α‐hydroxy ynamides. The BF3‐catalyzed intramolecular dehydrative condensation of the resulting α‐hydroxy enamides afforded tricyclic isoindolones in good yields. α‐Regioselective addition of 1,3‐dicarbonyl compounds to N‐alkynyl‐3‐hydroxyisoindolin‐1‐ones (α‐hydroxy ynamides) was accomplished with the use of NiII salt catalysts. This addition proceeded via a keteneimine intermediate, and the adducts were converted into tricyclic isoindolones. [ABSTRACT FROM AUTHOR]

Concise syntheses of 9-methoxyellipticine, 3,4-dihydroellipticine (µ-alkaloid D), 1,2,3,4-tetrahydroellipticine, 2-methyl-1,2,3,4-tetrahydroellipticine, olivacine, 3,4-dihydroolivacine, (±)-guatambuine, and (±)-janetine were developed starting from hexatriene intermediates readily obtained by Pd-catalyzed tandem cyclization/cross-coupling reaction of indolylborates. The route enables the facile construction of pyrido[4,3- b]carbazoles by Cu-catalyzed 6π-electrocyclization and subsequent transformation of the pyridocarbazole intermediates into pyrido[4,3- b]carbazole alkaloids. [ABSTRACT FROM AUTHOR]

A new approach to form iminoisocoumarins from readily available and stable 2-alkynylbenzamides was developed by using a tandem copper-catalyzed N-arylation and regioselective 6- endo- dig cyclization in the presence of diaryliodonium salts, a copper catalyst, and 2,6-di- tert-butylpyridine. The arylation occurred at the nitrogen atom rather than the oxygen atom of the amide group, the alkynyl carbon, or the benzene ring of the benzamide. Cyclization occurred through a preferential nucleophilic attack by the oxygen rather than the nitrogen atom of the amide group to produce iminoisocoumarin derivatives in good to moderate yields. [ABSTRACT FROM AUTHOR]

Starting from ortho-alkynylbenzaldehydes and ortho-alkynylanilines, In(OTt)3-catalyzed synthesis of ring-condensed heteroaromatic compounds was developed via a domino intramolecular nucleophilic attack/intermolecular cycloaddition/dehydration reaction. [ABSTRACT FROM AUTHOR]

Novel indium-mediated radical cyclization reactions of aliphatic iodoalkynes have been studied. Treatment of iodoalkynes with a catalytic amount of In (0.1 equiv) and I2 (0.05 equiv) promotes atom-transfer 5-exo cyclization to give five-membered alkenyl iodides. In contrast, reaction with In (2 equiv) and I2 (1 equiv) yields reductive 5-exo cyclization products via the same 5-exo cyclization. Both processes are most likely initiated by low-valent indium species. To demonstrate versatility of these reactions, optically active HIV protease inhibitors were synthesized by this reductive cyclization method. Among them, several products, which contain a hydroxyethylamine dipeptide isostere as a transition state-mimicking substructure, proved to possess potent activity (IC50 = 5-39 nM) against a wide spectrum of HIV strains, including multidrug-resistant variants. [ABSTRACT FROM AUTHOR]

Upon treatment with In and I2, mono-substituted alkenes having an iodine substituent at the δ-position of the tether gave the corresponding iodinated cyclic compounds, whereas di- and tri-substituted alkenes gave the corresponding hydroxylated cyclic compounds. Alkenes bearing leaving groups at the allylic position were transformed only to the corresponding vinyl substituted cyclic compounds. On the other hand, alkynes bearing good leaving groups at the propargylic position gave allenic products selectively. [Copyright &y& Elsevier]

Novel indium-mediated reactions have been studied. Treatment of iodoalkyne with In (0.5 equiv.) and I2 (0.5 equiv.) in MeOH promotes the atom-transfer 5-exo-cyclization. In contrast, the reaction with In (2 equiv.) and I2 (1 equiv.) gives rise to a reductive 5-exo-cyclized product. [Copyright &y& Elsevier]

An efficient one-pot synthesis of 1,2,3-triazole-fused isoindoles from o -alkynylbenzaldehydes and trimethylsilyl azide (TMSN 3 ) is reported. The reaction proceeds through the formation of a diazide intermediate and a subsequent intramolecular azide-alkyne cycloaddition, providing a novel access to a variety of 8-azido-8 H -[1,2,3]triazolo[5,1- a ]isoindoles in high yields. [ABSTRACT FROM AUTHOR]

By using carbophilic Lewis acids, ln(OTf)3, NiCl2, and AuCl(PPh3)/AgNTf2, a concise and efficient synthesis of 1,3-disubstituted 1,2-dihydroisoquinolines has been achieved via tandem nucleophilic addition and cyclization of 2-(1-alkynyl)arylaldimines. Addition of proton sources such as water, CF3CH2OH, and 2,6-di-tert-butyl-4-methoxyphenol was essential for the Lewis acid-catalyzed tandem reactions with organometallic reagents. By switching these catalysts, various types of nucleophiles such as allylstannanes, silyl enol ethers, alkenylboronic acids, and active methylene compounds could be introduced at the C1 position of 1,2-dihydroisoquinolines in this transformation. Furthermore, this method proved to be applicable to the synthesis of 1H-isochromene derivatives via the same tandem reaction of 2-(1-alkynyl)-arylaldehydes. [ABSTRACT FROM AUTHOR]

Abstract: Direct, efficient syntheses of the benzimidazo[2,1-a]isoquinoline ring system have been achieved with 2-bromoarylaldehydes, terminal alkynes, and 1,2-phenylenediamines by a microwave-accelerated tandem process in which a Sonogashira coupling, 5-endo cyclization, oxidative aromatization, and 6-endo cyclization can be performed in a single synthetic operation. [Copyright &y& Elsevier]

affording a series of iminoisocoumarins [ABSTRACT FROM AUTHOR]