An unexpected copper catalyzed ‘reduction’ of an arylazide to amine through the formation of a nitrene intermediate

Azido nitrobenzoxadiazole (NBD) was observed to undergo a ‘reduction’ reaction in the absence of an obvious reducing agent, leading to amine formation. In the presence of an excess amount of DMSO, a sulfoxide conjugate was also formed. The ratio of these two products was both temperature- and solven...

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Bibliographic Details
Published in:Tetrahedron 2013-06, Vol.69 (25), p.5079-5085
Main Authors: Peng, Hanjing, Dornevil, Kednerlin H., Draganov, Alexander B., Chen, Weixuan, Dai, Chaofeng, Nelson, William H., Liu, Aimin, Wang, Binghe
Format: Article
Language:English
Subjects:
Azide
EPR
NBD
Nitrene
Reduction
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Summary:Azido nitrobenzoxadiazole (NBD) was observed to undergo a ‘reduction’ reaction in the absence of an obvious reducing agent, leading to amine formation. In the presence of an excess amount of DMSO, a sulfoxide conjugate was also formed. The ratio of these two products was both temperature- and solvent-dependent, with the addition of water significantly enhancing the ratio of the ‘reduction’ product. Two intermediates of the azido-NBD reaction in DMSO were trapped and characterized by low-temperature EPR spectroscopy. One was an organic free radical (S=1/2) and another was a triplet nitrene (S=1) species. A mechanism was proposed based on the characterized free radical and triplet intermediates. [Display omitted]
ISSN:0040-4020
1464-5416
DOI:10.1016/j.tet.2013.04.091