Synthesis and Electronic Properties of Sterically Demanding N-Arylphenothiazines and Unexpected Buchwald-Hartwig Aminations Adam W. Franz, †,‡ Frank Rominger, ‡,§ and Thomas J. J. Mu ¨ller* ,†,‡ Institut fu ¨r Organische Chemie und Makromolekulare Chemie, Heinrich-Heine UniVersita ¨t Du ¨sseldorf, strasse 1, D-40225 Du ¨sseldorf, Germany, and Organisch-Chemisches Institut, Ruprecht-Karls-UniVersita ¨t Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany thomasjj.mueller@uni-duesseldorf.de ReceiVed NoVember 5, 2007 Phenothiazine is coupled under Buchwald-Hartwig conditions with bromo anthracenes and perylene as substrates to give phenothiazine-anthracene and phenothiazine-perylene dyads and triads. Investigation of the electronic properties of these sterically demanding N-aryl phenothiazines by absorption and emission spectroscopy, cyclic voltammetry, and DFT calculations revealed that the individual chromophores are decoupled in the electronic ground state but show unique electronic communication in the excited state. For the anthracenyl-bridged diphenothiazine an intense electronic coupling of the phenothiazinyl units is detected upon oxidation. Besides, attempts to synthesize phenothiazine compounds with even more sterically demanding aryl substituents in the 10-position under N-arylation conditions gave rise to the formation of quite unexpected products of arylation and/or oxidative coupling. The folding angle of the phenothiazine in a consanguineous series correlates well with the first oxidation potential. Introduction Phenothiazines belong to an important class of tricyclic nitrogen-sulfur heterocycles, 1 with a broad spectrum of phar- macological activity. 2 Most interestingly, phenothiazines are also able to cleave DNA upon photochemical induction. 3 As a consequence of a low oxidation potential, they readily form stable radical cations and some of their physiological activity can be attributed to this circumstance. 4 Furthermore, the radical cations give rise to a fingerprint of characteristic, deep-colored † Heinrich-Heine Universita ¨t Du ¨sseldorf. ‡ Ruprecht-Karls-Universita ¨t Heidelberg. § X-ray structure analyses. (1) Sainsbury, M. In ComprehensiVe Heterocyclic Chemistry; Katritzky, A. R., Rees, C. W., Eds.; Pergamon: Oxford, UK, 1984; Vol. 3, p 995. 10.1021/jo702389v CCC: $40.75 © 2008 American Chemical Society J. Org. Chem. 2008, 73, 1795-1802 1795 Published on Web 02/05/2008