Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

• Yara Cristina Marchioro Barbosa,
• Guilherme Caneppele Paveglio,
• Claudio Martin Pereira de Pereira,
• Sidnei Moura,
• Cristiane Storck Schwalm,
• Gleison Antonio Casagrande and
• Lucas Pizzuti

Beilstein J. Org. Chem. 2022, 18, 1079–1087, doi:10.3762/bjoc.18.110

• de Caxias do Sul, 95070-560, Caxias do Sul-RS, Brazil 10.3762/bjoc.18.110 Abstract The broad application of 1H-indazoles has prompted the development of several approaches for the synthesis of such compounds, including metal-free, palladium-, or copper-promoted intramolecular N-arylation of in situ

• available and less expensive than brominated analogs. Seeking to cover a lack in the literature, this work reports a convenient protocol for the synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of o-chlorinated arylhydrazones. Therefore, a series of seven N

• ‐substituents, and others suffer from poor regioselectivity for substrates without a directing group [18][19][21][22]. On the other hand, methods based on metal-free [23], palladium- [24][25], and copper-promoted [26][27][28][29][30][31] intramolecular N-arylation of in situ-generated or isolated o

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• underwent an intramolecular N-arylation to provide the cyclized product 2. The overall yield in this three-step sequence is 72% based on recovered diaryl ether. Interestingly, an unusually stable iodine(III) intermediate was formed in the O-arylation. This species survived neutral work-up and could be

Recent advances in copper-catalyzed asymmetric coupling reactions

• Fengtao Zhou and
• Qian Cai

Beilstein J. Org. Chem. 2015, 11, 2600–2615, doi:10.3762/bjoc.11.280

• good yields and with excellent enantioselectivities (Scheme 20). Kinetic resolution is another strategy for asymmetric aryl C–N coupling reactions. Cai et al. [50] developed a copper-catalyzed asymmetric intramolecular N-arylation of rac-2-amino-3-(2-iodoaryl)propionates and rac-2-amino-4-(2-iodoaryl

A concise and efficient synthesis of benzimidazo[1,2-c]quinazolines through CuI-catalyzed intramolecular N-arylations

• Xinlong Pang,
• Chao Chen,
• Ming Li and
• Chanjuan Xi

Beilstein J. Org. Chem. 2015, 11, 2365–2369, doi:10.3762/bjoc.11.258

• are not readily available and need harsh conditions. Herein we report a CuI-catalyzed concise and efficient method for the synthesis of benzimidazo[1,2-c]quinazoline derivatives through the intramolecular N-arylation reaction of bromo-substituted quinazolin-4(3H)-imines that are easily prepared from o

• showing the cleavage of the quinazoline ring rather than the imidazole ring [26]. Conclusion We have demonstrated a CuI-catalyzed pathway to produce functionalized benzimidazo[1,2-c]quinazoline derivatives from bromo-substituted quinazolin-4(3H)-imines through a selective intramolecular N-arylation

• drawing of 5, [C20H16F2N4O]·2Cl·H2O with 35% probability ellipsoids, showing the atomic numbering scheme. CuI-catalyzed synthesis of benzimidazo[1,2-c]quinazolines 4 by intramolecular N-arylation of bromo-substituted quinazolin-4(3H)-imine derivatives 3. Cu-catalyzed reaction of o-cyanoaniline (1a

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• rather expensive; therefore efforts were made to replace them with cheaper analogues. One successful approach included iron(III) acetylacetonate in acetic acid as catalytic agent (Scheme 16) [37], whereby O-acetyl oximes obtained from 2′-arylacetophenones underwent N–O bond cleavage and intramolecular N

• -arylation. The following conventional cross-coupling or directed C–H arylation resulted in substituted phenanthridines. Homolytic aromatic substitution (HAS) by an aryl radical was used for the construction of biaryl motifs as alternative to transition metal-catalysed C–H bond arylation. That approach was

Microwave-assisted synthesis of 5,6-dihydroindolo[1,2-a]quinoxaline derivatives through copper-catalyzed intramolecular N-arylation

• Fei Zhao,
• Lei Zhang,
• Hailong Liu,
• Shengbin Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2013, 9, 2463–2469, doi:10.3762/bjoc.9.285

• synthesize 5,6-dihydroindolo[1,2-a]quinoxaline derivatives by CuI-catalyzed intramolecular N-arylation under microwave irradiation. This method rapidly afforded the tetracyclic products with good to excellent yields (83–97%) in short reaction times (45–60 min). Keywords: copper; 5,6-dihydroindolo[1,2-a

• ]quinoxaline; intramolecular N-arylation; microwave irradiation; Introduction The indole scaffold is considered as a privileged structure because of its ubiquitous presence in a large number of natural products and pharmaceutical agents [1][2][3][4][5][6]. In particular, indole-fused heterocycles have

• intramolecular N-arylation with good to excellent yields. Results and Discussion The required cyclization precursors 1, aryl substituted (1H-indol-2-yl)methanamines, were easily prepared by reductive amination of 1H-indole-2-carbaldehydes with 2-haloanilines in good yields (Scheme 1). Initial screening

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• a Pd-catalyzed cascade sequence, involving an alkenyl amination, a C-arylation and a subsequent intramolecular N-arylation, was developed by Barluenga and coworkers for the preparation of indole derivatives 68 [37]. Here, equimolecular amounts of haloalkene 65, o-dihaloarene 66, and amines are mixed

• basic media. A subsequent Pd-mediated intermolecular alkylation with the dihalogeno substrate followed by an intramolecular N-arylation furnished 2-substituted indoles 68. In this cascade reaction, the palladium catalyst intervenes in three different coupling reactions: Intermolecular N-alkenylation, C

• -arylation and intramolecular N-arylation (Scheme 29). The palladium-mediated amination reaction coupled with a nitrogen–carbon bond-forming reaction was also used for the stereoselective synthesis of N-aryl-2-benzylpyrrolidines 71 starting from linear 4-pentenylamine and its derivatives [38]. In this tandem

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• , carbamates, N-heterocycles, enamines and intramolecular N-arylation reactions [45]. We compare here the success of the different C–N-arylation reactions as applied to the synthesis of more complex structures and discuss selected examples of palladium- and copper-mediated reactions for the synthesis of

• cyclization step by intramolecular N-arylation of 14 was developed that led to improved access to compound 15 due to better availability of the starting material and a simple palladium source. Under optimized conditions, palladium catalysis yielded the tricyclic skeleton 15 in 91% and reduced the amount of

Synthesis of dihydrophenanthridines by a sequence of Ugi-4CR and palladium- catalyzed intramolecular C-H functionalization

• Florence Bonnaterre,
• Michèle Bois-Choussy and
• Jieping Zhu

Beilstein J. Org. Chem. 2008, 4, No. 10, doi:10.3762/bjoc.4.10

• reaction pathway leading to the formation of oxindole via an intramolecular N-arylation process was not observed under these conditions [25][26][27]. The preferential formation of compound 1a indicated that cyclization via palladium-catalyzed CH functionalization could be, under appropriate conditions, a