Please use this identifier to cite or link to this item: https://doi.org/10.1021/jo0256991
Title: 2-Pyrazinylnitrene and 4-pyrimidylnitrene. Ring expansion to 1,3,5-triazacyclohepta-1,2,4,6-tetraene and ring opening to (2-isocyanovinyl) carbodiimide
Authors: Addicott, C.
Wong, M.W. 
Wentrup, C.
Issue Date: 29-Nov-2002
Citation: Addicott, C., Wong, M.W., Wentrup, C. (2002-11-29). 2-Pyrazinylnitrene and 4-pyrimidylnitrene. Ring expansion to 1,3,5-triazacyclohepta-1,2,4,6-tetraene and ring opening to (2-isocyanovinyl) carbodiimide. Journal of Organic Chemistry 67 (24) : 8538-8546. ScholarBank@NUS Repository. https://doi.org/10.1021/jo0256991
Abstract: 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 15N-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.
Source Title: Journal of Organic Chemistry
URI: http://scholarbank.nus.edu.sg/handle/10635/92908
ISSN: 00223263
DOI: 10.1021/jo0256991
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