New Strategy by C-H Activation: Arylation of Alquenes and Alkylation of Arenes Mediated by Potassium tert-Butoxide and Light

BUDÉN, MARÍA E.; GUASTAVINO, JAVIER F.; ROSSI, ROBERTO A.

Foz do Iguazú

Congreso; 12th Latin American Conference on Physical Organic Chemistry; 2013

Universidade Federal de Santa Catarina

Aryl halides or alkyls halides (RX) that do not undergo SN2 nor SN1 reaction could be usually activated by electron transfer (ET) to participate in substitution reactions (SRN1 reaction).1 This mechanism is a chain process with radicals and radical anions as intermediates (Scheme 1, A). As t-BuOK can form [RX]-. by ET in photostimulated SRN1 reactions,2 we speculated that the arylation or alkenylation could only be achieved with t-BuOK and light (Scheme 1, B). In the present work, we present two different approaches: alkylation of arenes (benzene and heterocycles) and C-H alkenylation of haloarenes,3 by photoinduced ET without the addition of transition metals or ligands (Scheme 2 and 3).   In the photostimulated reaction, 1-iodoadamantane (1-IAd) reacted with benzene (10 equiv) and t-BuOK (3 equiv) in DMSO, which after 3 h gave 95% yield of 1-Ad-Ph (Scheme 2).The formation of radicals and radical anions is a key step (Scheme 1, B), were supported by experiments performed in the presence of the radical scavenger and a good acceptor electron such as m-dinitrobenzene which inhibited the reactions. Moreover, the reaction of 1-IAd with thiophene, gave the product 1-Ad-thiophene was obtained in good yields. This environmentally friendly methodology promotes effectively the alkenylation of a broad range of aryl and heteroaryl halides. Moreover, double alkenylation were achieved to construct extended p?electron systems. We will discuss the scope and limitation of this novel strategy of reactions. 1) R. A. Rossi, A. B. Pierini, A. B. Peñéñory, Chem. Rev. 2003, 103, 71-168. 2) L. C. Schmidt, J. E. Argüello, A. B. Peñéñory, J. Org. Chem. 2007, 72, 2936-2944. 3) E. Shirakawa, X. Zhang, T. Hayashi, Angew. Chem. Int. Ed. Engl. 2011, 50, 4671-4674. b) C. L. Sun, Y. F. Gu, B. Wang, Z. J. Shi, Chem. Eur. J. 2011, 17, 10844-10847.