Dechlorination of 6, 13-Dichlorotriphenodioxazine and Its Analogues

Abstract

Dehalogenation with excess tin powder in polyphosphoric acid was used for the synthesis of triphenodioxazine (5, 12-dioxa-7, 14-diazapentacene) [5 a] and its analogues. For example, 6, 13-dichlorotriphenodioxazine [4 a] was converted to [5 a] in 55.8% yield. Similarly, 3, 10- dibromo- [4 b], 3, 10-dichloro- [4 c], and 1, 2: 8, 9-dibenzo- [4 d] derivatives of [4 a] were reduced to the corresponding halogen free compounds.
A facile route to triphenodithiazine (5, 12-dithia-7, 14-diazapentacene) [9] was also established with these reagents. Replacement of halogenes by hydrogens in these heterocycles brought about a decrease in melting point and strong hypsochromic shifts in electronic spectrum.