Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

• Youlong Du,
• Haibo Mei,
• Ata Makarem,
• Ramin Javahershenas,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2024, 20, 212–219, doi:10.3762/bjoc.20.21

• challenging. On the other hand, several interesting transformations of nitrile ylides from diazo compounds have been developed in the past years [31][32][33][34][35][36][37][38]. In particular, acylglycine esters could be easily constructed with ester-containing diazo compounds as the starting materials. For

• example, Wan and co-workers developed a cascade reaction of α-diazo esters, nitriles, and carboxylic acids via the generation of nitrile ylides and Mumm rearrangement affording unsymmetric diacyl α-amino acid esters as products (Scheme 1a) [39]. In 2017, Zhang, Hu, and co-workers developed a Cu-catalyzed

• [42][43][44][45][46][47][48][49], we sought to develop reactions of the unexplored β-trifluoromethyl β-diazo esters. We hypothesized that nitrile ylides, in situ generated from nitriles and β-trifluoromethyl β-amino esters, could also react with carboxylic acids to give nitriliums, which then could

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• , [3 + 2]-cycloadditions leading to five-membered heterocycles are less often employed in spite of the high dipolarophilicity of the α,β-unsaturated diketone system [6][7][8][9]. Notably, in the already reported reactions of propargylic 1,3-dipoles, such as nitrile oxides or nitrile ylides, with 1,4

Domino reactions of 2H-azirines with acylketenes from furan-2,3-diones: Competition between the formation of ortho-fused and bridged heterocyclic systems

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Viktoriia V. Pakalnis,
• Roman O. Iakovenko and
• Dmitry S. Yufit

Beilstein J. Org. Chem. 2014, 10, 784–793, doi:10.3762/bjoc.10.74

• into pyrazines, even when stored in a fridge. Different mechanisms of dimerization were assumed, such as formation and dimerization of nitrile ylides [37][40], hydrolysis to α-aminoketenes followed by condensation [37][41], intermediate formation of metal complexes in the reaction mediated by metals

• [41][43][46]. It was found that water [37], Brønsted [44][48] and Lewis acids [40][41][43] facilitate the formation of pyrazine derivatives. 2H-Azirines undergo ring opening on electronic excitation to give nitrile ylides [50]. Nitrile ylide formation under thermal conditions even from such strained

• compounds as 2H-azirines needs to overcome a quite high energy barrier. According to calculations at the DFT B3LYP/6-31G(d) level the free energy barriers to formation of nitrile ylides 13a–c from azirines 2a–c are 48.4, 47.6, 47.9 kcal·mol−1 (353 K, benzene (PCM)), respectively. Therefore the process of

[3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

• Stephan Cludius-Brandt,
• Lukas Kupracz and
• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1745–1750, doi:10.3762/bjoc.9.201

• with thermal formation of 2H-azirines. Photochemically, the ring of the 2H-azirines was opened to yield the nitrile ylides, which underwent a [3 + 2]-cycloaddition with 1,3-dipolarophiles. When diisopropyl azodicarboxylate serves as the dipolarophile, 1,3,4-triazoles become directly accessible starting

• from the corresponding vinyl azide. Keywords: azirines; cycloaddition; flow chemistry; flow reactors; inductive heating; nitrile ylides; photochemistry; vinyl azides; Introduction Recently, photochemistry has seen a renaissance despite the fact that under batch conditions specialized reaction vessels

• to perform many transformations that are hardly possible under thermal conditions. This includes photocatalytic reactions that have seen an immense interest lately [1]. Nitrile ylides 3 are 1,3-dipoles that have served for the preparation of different five-membered N-heterocycles in 1,3-dipolar

4-Pyridylnitrene and 2-pyrazinylcarbene

• Curt Wentrup,
• Ales Reisinger and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 754–760, doi:10.3762/bjoc.9.85

• -diazacyclohepta-1,2,4,6-tetraene (20). Further photolysis causes ring opening to the ketenimine 27. Keywords: carbene–nitrene interconversion; diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediates; Introduction The carbene–nitrene interconversion exemplified with

• nitrenes possessing a 1,3-relationship between a nitrene centre and a ring nitrogen atom and leads to nitrile ylides, such as 9 in the case of 3-pyridylnitrene (7), whereby the actual ring opening may take place in either the nitrene itself or the ring-expanded ketenimine 8 (Scheme 2) [6][7][8]. A 1,7-H

• . Related nitrile ylides are known to undergo very facile 1,7-H shifts (see, e.g., Scheme 2) [3][6]. Both the nitrile ylide and the ring-expanded ketenimine were observed in the corresponding benzannelated systems, viz 4-azidoquinoline and 2-diazomethylquinoxaline [17], and the ylidic ring opening is very

3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

• Curt Wentrup,
• Nguyen Mong Lan,
• Adelheid Lukosch,
• Pawel Bednarek and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84

• either the nitrenes or the diazacycloheptatetraenes to nitrile ylides. Keywords: carbene-nitrene interconversion; diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediates; Introduction A multitude of rearrangements of heterocyclic nitrenes have been described

• to the formation of glutacononitriles in low yields [12]. In contrast, 3-pyridylnitrene (10) undergoes a different type of ring opening to the observable nitrile ylide 11 and subsequently the ketenimine 12 (Scheme 3) [13]. Nitrile imines [14] and nitrile ylides [15][16] may have either allenic or

• pyrimidinylcarbenes 28 and 33 to diazacycloheptatetraenes 29 and 34, ring contraction to 3-pyridylnitrenes 30 and 35 and/or ring opening to nitrile ylides 31 and 37, and ring closure to cyanopyrroles (Scheme 9). In the case of the 4-pyrimidinylcarbene 28 a direct ring opening of the diazacycloheptatetraene 29 to the