Selective cross-dehydrogenative C–O coupling of N-hydroxy compounds with pyrazolones. Introduction of the diacetyliminoxyl radical into the practice of organic synthesis

Igor B. Krylov; Stanislav A. Paveliev; Boris N. Shelimov; Boris V. Lokshin; Irina A. Garbuzova; Viktor A. Tafeenko; Vladimir V. Chernyshev; Alexander S. Budnikov; Gennady I. Nikishin; Alexander O. Terent'ev

doi:10.1039/C7QO00447H

Selective cross-dehydrogenative C–O coupling of N-hydroxy compounds with pyrazolones. Introduction of the diacetyliminoxyl radical into the practice of organic synthesis†

Igor B. Krylov,

^a Stanislav A. Paveliev,^a Boris N. Shelimov,^a Boris V. Lokshin,^b Irina A. Garbuzova,^b Viktor A. Tafeenko,^c Vladimir V. Chernyshev,^cd Alexander S. Budnikov,^ae Gennady I. Nikishin^a and Alexander O. Terent'ev

*^a

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* Corresponding authors

^a N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences, 47 Leninsky prosp., Moscow 119991, Russian Federation
E-mail: alterex@yandex.ru

^b A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28 Vavilova St., Moscow 119991, Russian Federation

^c Department of Chemistry, M.V. Lomonosov Moscow State University, 1-3 Leninskie Gory, Moscow 119991, Russian Federation

^d A. N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 31 Leninsky prospect, Moscow 119071, Russian Federation

^e Higher Chemical College of the Russian Academy of Sciences, Mendeleev University of Chemical Technology of Russia, 9 Miusskaya sq., Moscow 125047, Russian Federation

Abstract

Oxidative C–O coupling of pyrazolones with N-hydroxy compounds of different classes (N-hydroxyphthalimide, N-hydroxybenzotriazole, oximes) was achieved; both one-electron oxidants (Fe(ClO₄)₃, (NH₄)₂Ce(NO₃)₆) and two-electron oxidants (PhI(OAc)₂, Pb(OAc)₄) are applicable, and the yields reach 91%. Apparently, the coupling proceeds via the formation of N-oxyl radicals from N-hydroxy compounds. One of the N-oxyl intermediates, the diacetyliminoxyl radical, was found to be exclusively stable in solution in spite of being sterically unhindered; it was isolated from an oxidant and used as a new reagent for the synthesis and mechanism study. The products of C–O coupling of pyrazolones with N-hydroxyphthalimide can be easily transformed into aminooxy compounds, valuable substances for combinatorial chemistry.

This article is part of the themed collection: FOCUS: Radical-involved chemical transformations

Organic Chemistry Frontiers

Selective cross-dehydrogenative C–O coupling of N-hydroxy compounds with pyrazolones. Introduction of the diacetyliminoxyl radical into the practice of organic synthesis†

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Selective cross-dehydrogenative C–O coupling of N-hydroxy compounds with pyrazolones. Introduction of the diacetyliminoxyl radical into the practice of organic synthesis

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