Synthesis of Nitrogen Heterocycles by Domino C–N Coupling/Hydroamination Reactions

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The cyclization of various nucleophiles, such as 1,3-dicarbonyl compounds, 1,3-bis(silyloxy)-1,3-butadienes, hydrazones, hydroxylamine, amidines, thioglycolic esters, heterocyclic enamines and others, with 4-chlorocoumarins, containing an electron-withdrawing group at position 3, allows for a convenient synthesis of a great variety of benzo[c]coumarins and related fused coumarins. Suzuki–Miyaura reactions of coumarin-derived bis(triflates) result in formation of arylated coumarins with excellent regioselectivity that is controlled by electronic and steric features of the substrate. The combination of Suzuki–Miyaura with lactonization reactions of carba- and heterocyclic substrates allows for the synthesis of benzo[c]coumarins and of other fused coumarins. Domino Michael–retro-Michael–lactonization reactions of 1,3-bis(silyloxy)-1,3-butadienes with chromones provide a convenient access to hydroxylated benzo[c]coumarins. In a related approach, fused coumarins were prepared by domino reactions of heterocyclic enamines with chromone-3-carboxylic acids.1 Introduction2 Reactions of 3-Acceptor-4-chlorocoumarins3 Reactions of Coumarin Triflates4 Synthesis of Fused Coumarins5 Conclusions

Section: Sonogashira/hydroamination Reactionsmentioning

confidence: 99%

Adventures in Coumarin Chemistry

Langer

2024

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“…reactions. The reaction of TFAA with 3-alkynyl-4-pyrrolylpyridines 9a-g afforded pyrrolo[1,2-a] [1,6]naphthyridines 10a-g in 49-81% yields (Scheme 3). 13 In general, the yields were very good and only dropped in the case of product 10d containing a methoxy group.…”

Section: Account Synlettmentioning

confidence: 99%

“…Starting in 2005, during which time I was already a full professor at the University of Rostock, my students and I started to develop regioselective 3 Pd-catalyzed cross-coupling reactions with special emphasis on their application to polyhalogenated heterocycles. 4 Later, we investigated the combination of such reactions with cyclizations by twofold Buchwald-Hartwig reactions, 5 hydroamination reactions, 6 and cycloisomerizations. 7,8 In the context of our studies related to cycloisomerization reactions, we also became more and more interested in the synthesis of new heterocyclic core structures and, last but not the least, in their optical, electrochemical and electronic properties.…”

mentioning

confidence: 99%

Synthesis of Heterocycles by a C–C Cross-Coupling/Alkyne-Carbonyl-Metathesis Strategy

Langer

2024

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The present article presents a personal account on the synthesis of heterocycles by the combination of regioselective Pd-catalyzed cross-coupling reactions of polyhalogenated heterocycles, i.e., Suzuki–Miyaura and Sonogashira reactions, with alkyne-carbonyl-metathesis (ACM) reactions. The products, which show interesting optical, electronic or medicinal properties, are not readily available by other methods.

“…In 2005, my co-workers and I started to develop regioselective Pd-catalyzed coupling reactions of polyhalogenated heterocycles 6 and of bis(triflates). 7 Later, this work was extended by combination with twofold Buchwald-Hartwig reactions, 8 domino CN-coupling / hydroamination, 9 and cycloisomerization reactions. 10 In this context, I also became more and more interested in the synthesis of new heterocyclic core structures and their optical, electrochemical and electronic properties.…”

Section: Introductionmentioning

confidence: 99%

Adventures in CH-Arylation Chemistry

Langer

2024

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The present article provides a personalized account on CH-arylation reactions employed for the synthesis of heterocycles. The presence of a nitro group allowed for direct and regioselective CH-arylations of pyrazoles, imidazoles, indoles and a variety of purine analogues. Direct CH-arylations without the presence of an activating nitro-group were employed for inter- and intramolecular reactions of purine derivatives, which allowed for the synthesis of a great variety of polycyclic systems. Domino C–N coupling / hydroamination / CH-activation reactions of diarylacetylenes with anilines allowed for the synthesis of polycondensated N-heterocycles. Products include indolo- and azaindolo[1,2-f]phenanthridines, quinolino[3′,4′:4,5]pyrrolo[1,2-f]phenanthridines, pyrimido[5′,4′:4,5]pyrrolo[1,2-f]phenanthridines, and benzothieno[2′,3′:4,5]pyrrolo[1,2-f]phenanthridines. The reaction of N-heterocycles, such as indoles, with 1,1-difluoroalkenes resulted in a twofold addition-elimination reaction to give 1,1-diaminoalkenes, which were transformed by CH-arylation into various polycondensated heterocycles, such as indoloisoquinolines, thienoindolizines, oxepines and helicenes. Pyridofluoranthenes, diindenopyrene and azadiindenopyrenes were prepared by a combination of Pd-catalyzed cross-coupling reactions with acid-mediated cycloisomerizations and Pd-catalyzed intramolecular CH-arylations. Bis(carbazoles), benzodithiazoles, benzodithiophenes and 2,5-diarylpyrroles were prepared by inter- and intramolecular CH-arylation reactions.