The Suzuki-Miyaura reaction as a tool for modification of phenoxyl-nitroxyl radicals of the 4 H-imidazole N-oxide series

Yury A Ten; Oleg G Salnikov; Svetlana A Amitina; Dmitri V Stass; Tatyana V Rybalova; Maxim S Kazantsev; Artem S Bogomyakov; Evgeny A Mostovich; Dmitrii G Mazhukin

doi:10.1039/c8ra05103h

The Suzuki-Miyaura reaction as a tool for modification of phenoxyl-nitroxyl radicals of the 4 H-imidazole N-oxide series

RSC Adv. 2018 Jul 20;8(46):26099-26107. doi: 10.1039/c8ra05103h. eCollection 2018 Jul 19.

Authors

Yury A Ten¹, Oleg G Salnikov², Svetlana A Amitina¹, Dmitri V Stass^{2

3}, Tatyana V Rybalova^{1

2}, Maxim S Kazantsev^{1

2}, Artem S Bogomyakov⁴, Evgeny A Mostovich^{1

2}, Dmitrii G Mazhukin^{1

2}

Affiliations

¹ NN Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS 9 Acad. Lavrentyeva Ave. Novosibirsk 630090 Russia, d-mazhukin@yandex.ru.
² Novosibirsk State University 2 Pirogova Str. Novosibirsk 630090 Russia.
³ Voevodsky Institute of Chemical Kinetics and Combustion SB RAS 3 Institutskaya Str. Novosibirsk 630090 Russia.
⁴ International Tomography Center SB RAS 3A Institutskaya Str. Novosibirsk 630090 Russia.

Abstract

2-(3,5-Di-tert-butyl-4-hydroxyphenyl)-5-(4-iodophenyl)-4,4-dimethyl-4H-imidazole 3-oxide reacts with phenylboronic acid and its substituted derivatives in a cross-coupling reaction of the Suzuki-Miyaura type to form 5-biphenyl derivatives of 4H-imidazole-N-oxide. Interaction of the same compound with B₂(pin)₂ in the presence of PdCl₂(PPh₃)₂ proceeds through the formation of intermediate 1,3,2-dioxoborolane and leads to the product of homocoupling: biphenyl-bis(imidazole). Oxidation of the resultant imidazoles with lead dioxide quantitatively yields stable conjugated phenoxyl-nitroxyl mono- and diradicals, which are of interest as electroactive paramagnetic materials. The crystal structure of the monoradical, 2,6-di-tert-butyl-4-[1-oxido-4-(biphenyl-4-yl)-5,5-dimethyl-1H-imidazole-2(5H)-ylidene]cyclohex-2,5-dienone, its magnetic susceptibility, EPR spectra of the obtained hybrid radicals in solution, and cyclic voltammetry characteristics of 4H-imidazoles were studied.