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Synthesis 2010(12): 2075-2079  
DOI: 10.1055/s-0029-1218782
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Catalytic Oxidation of N-Phenylamidrazones to 1,3-Diphenyl-1,4-dihydro-1,2,4-benzotriazin-4-yls: An Improved Synthesis of Blatter’s Radical

Panayiotis A. Koutentis*, Daniele Lo Re
Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
e-Mail: koutenti@ucy.ac.cy; Fax: +357(22)892809;
Further Information

Publication History

Received 18 January 2010
Publication Date:
10 May 2010 (online)

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Abstract

Blatter’s radical, 1,3-diphenyl-1,4-dihydro-1,2,4-benzotriazin-4-yl (1a, R = H), and several of its C-7 substituted analogues (R = CF3, Cl, Br, I, Me, OMe) were prepared in good-to-excellent yields through catalytic oxidation of the corresponding amidrazones by using palladium-on-carbon (1.6 mol%) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.1-1.0 equiv) in air. The reaction conditions were suitable for the preparation of Blatter’s radical on a one-gram scale in up to 87% yield.

Key words

catalysis - oxidations - ring closure - heterocycles - organic radicals - benzotriazines - DBU