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Transition-Metal-Free N-Arylation of Pyrazoles with Diaryliodonium Salts, Zsombor Gonda, Zoltán Novák, Chem. Eur. J.  2015, 21, 16801-16806. DOI: 10.1002/chem.201502995 | [Full Text Link] [Supp. Info. Link]

A new synthetic method was developed for the N-arylation of pyrazoles using diaryliodonium salts. The transformation does not require any transition-metal catalyst and provides the desired N-arylpyrazoles rapidly under mild reaction condition in the presence of aqueous ammonia solution as a mild base without the use of inert atmosphere. The chemoselectivity of unsymmetric diaryliodonium salts was also explored with large number of examples.

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Utilization of Copper-Catalyzed Carboarylation–Ring Closure for the Synthesis of New Oxazoline Derivatives, Ádám Sinai, Dóra Vangel, Tamás Gáti, Petra Bombicz, Zoltán Novák, Org. Lett. 2015, 17, 4136-4139. DOI: 10.1021/acs.orglett.5b01860 | [Full Text Link] [Supp. Info. LinkCIF]

A copper-catalyzed carboarylation–ring-closure strategy was used for the modular synthesis of oxazolines via the reaction of 1-aryl- and 1-alkylpropargylamides and diaryliodonium salts. The novel approach enables the efficient, modular synthesis of oxazoline derivatives bearing fully substituted exo double bonds.

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Multistep Continuous-Flow Synthesis of Condensed Benzothiazoles, Klára Lövei, István Greiner, János Éles, Áron Szigetvári, Miklós Dékány, Sándor Lévai, Zoltán Novák, György István Túrós, J. Flow Chem. 2015, 5, 74–81. DOI10.1556/1846.2015.00004 | [Full Text Link[Supp. Info Link]

In medicinal chemistry, the development of synthetic procedures for the access of new heterocyclic systems as potential scaffolds is elementary. Herein, we report our results on the formation of small drug-like heterocycles, utilizing flow chemistry. This approach enables the extension of the reaction parameter window, including high-pressure/high-temperature or hazardous chemistry. In our work, various novel condensed tricyclic benzothiazoles fused with furo- and thieno-rings were synthesized applying a multistep continuous-flow protocol. The process includes two ring closure steps and a nitro group reduction step. Batch and telescoped continuous-flow syntheses were also designed and performed.

Efficient Direct 2,2,2-Trifluoroethylation of Indoles via C-H Functionalization, Gergely László Tolnai, Anna Székely, Zita Makó, Tamás Gáti, János Daru, Tamás Bihari, Andras Stirling and Zoltán Novák, Chem. Commun. 201551, 4488-4491. DOI10.1039/C5CC00519A | [Supp. Info Link]

A novel highly C3 selective metal free trifluoroethylation of indoles using 2,2,2-trifuoroethyl(mesityl)-iodonium triflate was developed. The methodology enables the introduction of a trifluoroethyl group in a fast and efficient reaction under mild conditions with high functional group tolerance. Beyond the synthetic developments, quantum chemical calculations provide a deeper understanding of the transformation.

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Copper-Catalyzed Oxidative Ring Closure of ortho-Cyanoanilides with Hypervalent Iodonium Salts: Arylation–Ring Closure Approach to Iminobenzoxazines, Klára Aradi, Zoltán Novák, Adv. Synt. Catal. 2015357, 371-376. DOI: 10.1002/adsc.201400763 | [Full Text Link[Supp. Info Link]

A novel, highly modular synthetic methodology with high functional group tolerance was developed for the construction of iminobenzoxazine derivatives from ortho-cyanoanilides and diaryliodonium triflates via an oxidative arylation–cyclization path. The reaction is supposed to involve the formation of highly active aryl-copper(III) species. In this novel transformation, copper(II) triflate was used as catalyst in 1,2-dichloroethane or ethyl acetate and the reaction takes place at 75 °C in 2–16 h.

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Synthesis and Transformations of Oxygen Heterocycles, Zoltán Novák, András Kotschy, Topics in Heterocyclic Chemistry Vol. 45, 231-303. DOI: 10.1007/7081_2014_136

The recent developments in the transition metal-catalyzed synthesis and transformations of such oxygen-containing heteroaromatic systems are reviewed, where the oxygen is part of a five-membered ring.

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Mechanistic Study of Silver-Mediated Furan Formation by Oxidative Coupling, János Daru, Zsuzsanna Benda, Ádám Póti, Zoltán Novák,  András Stirling, Chem. Eur. J. 2014, 20, 15395–15400. DOI: 10.1002/chem.201404302 | [Full Text Link[Supp. Info Link]

Density functional calculations and experiments have been carried out to unravel the mechanism of a silver-mediated furan formation by oxidative coupling. Various possible reaction paths were considered and the most favorable channel has been identified on the basis of the calculated solvent-corrected Gibbs free-energy profiles. The mechanism represented by this route consists of a radical and a subsequent ionic route. The silver cation has a double role in the mechanism: it is the oxidant in the radical steps and the catalyst for the ionic steps, which is in accordance with the experimental observations. The two most important aspects of the optimal route are the formation of a silver–acetylide, reacting subsequently with the enolate radical, and the aromatic furan-ring formation in a single step at the latter, ionic segment of the reaction path. Our findings could explain several experimental observations, including the “key-promoter role” of silver, the preference for ionic cyclization, and the reduced reactivity of internal acetylides.

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Continuous-flow azide–alkyne cycloadditions with an effective bimetallic catalyst and a simple scavenger system, Sándor B. Ötvös, Gábor Hatoss, Ádám Georgiádes, Szabolcs Kovács, István M. Mándity, Zoltán Novák, Ferenc Fülöp, RSC Adv. 2014, 4, 46666-46674. DOI: 10.1039/C4RA07954J | [Supp. Info Link]

A flow chemistry-based technique is presented herein for Cu(I)-catalyzed azide–alkyne cycloadditions with a copper on iron bimetallic system as the catalyst and iron powder as a readily available copper scavenger. The method proved to be rapid and safe as compared with the conventional batch experiment; and by using an in-line copper scavenger, the level of copper impurities in the triazole products could readily be reduced to negligibly small amounts. The process was widely applicable, as not only terminal alkynes, but also various disubstituted acetylenes were nicely tolerated as dipolarophiles leading to useful 1,4,5-trisubstituted 1,2,3-triazoles.

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Efficient Copper-Catalyzed Trifluoromethylation of Aromatic and Heteroaromatic Iodides: The Beneficial Anchoring Effect of Borates, Zsombor Gonda, Szabolcs Kovács, Csaba Wéber, Tamás Gáti, Attila Mészáros, András Kotschy, Zoltán Novák, Org. Lett. 2014, 16, 4268-4271. DOI: 10.1021/ol501967c | [Full Text Info] [Supp. Info Link, NMR]

Efficient copper-catalyzed trifluoromethylation of aromatic iodides was achieved with TMSCF3 in the presence of trimethylborate. The Lewis acid was used to anchor the in situ generated trifluoromethyl anion and suppress its rapid decomposition. Broad applicability of the new trifluoromethylating reaction was demonstrated in the functionalization of different aromatic and heteroaromatic iodides.

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Utilization of a Copper on Iron Catalyst for the Synthesis of Biaryl Systems and Benzoxazines via Oxidative Arylation of Anilide Derivatives, Anna Székely, Ádám Sinai, Edina B. Tóth, Zoltán Novák, Synthesis 2014, 14, 1871-1880. DOI: 10.1055/s-0033-1338642 | [Full Text Link[Supp. Info Link]

Heterogeneous copper on iron catalyst serves as an efficient alternative copper source for arylation reactions using hypervalent iodonium salts. The copper(0) catalyst affords meta-arylation of pivalanilides, while 2-ethynylanilides undergo oxidative carbo­arylation–ring closure with diaryliodonium salts.

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