2-Pyrazinylnitrene and 4-Pyrimidylnitrene. Ring Expansion to 1,3,5-Triazacyclohepta-1,2,4,6-tetraene and Ring Opening to (2-Isocyanovinyl)carbodiimide
摘要:
Tetrazolo[1,5-a]pyrazine/2-azidopyrazine 9T/9A undergo photolysis in Ar matrix at cryogenic temperatures to yield 1,3,5-triazacyclohepta-1,2,4,6-tetraene 21 as the first observable intermediate, and 1-cyanoimidazole 11 and (2-isocyanovinyl)carbodiimide 22 as the final products. The latter tautomerizes to 2-(isocyanovinyl)cyanamide 23 on warming to 40 K. The same intermediate 21 and the same final products are obtained on matrix photolysis of the isomeric tetrazolo[1,5-c]pyrimidine/4-azidopyrimidine 24T/24A. These photolysis results as well as those of the previously reported thermal ring contraction of N-15-labeled 2-pyrazinyl- and 4-pyrimidylnitrenes to 1-cyanoimidazoles can all be rationalized in terms of selective ring opening of 21 or nitrine 10 to a nitrile ylide zwitterion 28 prior to formation of the final products, 11 and 22. The results are supported by high-level ab initio and DFT calculations (CASPT2-CASSCF(6,6), G3(MP2), and B3LYP/6-31+G*) of the energies and IR spectra of the intermediates and products.
catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradicalactivation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.
Copper(i) acetate-catalyzed azide–alkyne cycloaddition for highly efficient preparation of 1-(pyridin-2-yl)-1,2,3-triazoles
作者:Qun Zhang、Xinyan Wang、Chuanjie Cheng、Rui Zhu、Nan Liu、Yuefei Hu
DOI:10.1039/c2ob06942c
日期:——
A highly efficient copper(I)-catalyzed azideâalkyne cycloaddition (CuAAC) of 6-substituted tetrazolo[1,5-a]pyridines was developed for the preparation of 1-(pyridin-2-yl)-1,2,3-triazoles by simply using copper(I) acetate as a catalyst. The in situ formed HOAc played important dual roles and an activation of 2-azidopyridineâcopper(I) complex was observed.
intermolecular benzylic C(sp3)–H amination is developed utilizing 1,2,3,4-tetrazole as a nitrene precursor via iron catalysis. This method enables direct installation of 2-aminopyridine into the benzylic and heterobenzylic position. The methodselectively aminates 2° benzylic C(sp3)–H bond over the 3° and 1° benzylic C(sp3)–H bonds. Experimental studies reveal that the C(sp3)–H amination undergoes via the formation
Iron-Catalyzed Intermolecular C–N Cross-Coupling Reactions via Radical Activation Mechanism
作者:Subrata Das、Andreas W. Ehlers、Sima Patra、Bas de Bruin、Buddhadeb Chattopadhyay
DOI:10.1021/jacs.3c05627
日期:2023.7.12
aromatic and aliphatic azides with boronic acids under iron-catalyzed conditions. The amination follows an unprecedented metalloradical activation mechanism that is different from traditional metal-catalyzed C–N cross-coupling reactions. The scope of the reaction has been demonstrated by the employment of a large number of tetrazoles, azides, and boronic acids. Moreover, several late-stage aminations
A visible-light-driven iron-catalyzed C(sp3)–Hamination of diphenylmethane derivatives with 1,2,3,4-tetrazoles under mild conditions has been developed. The reaction proceeds with photosensitizer-free conditions and features satisfactory to good yields. Mechanistic studies revealed that the reaction proceeded via an iron–nitrene intermediate, and H atom abstraction was the rate-determining step. Computational