Convenient synthesis of a,δ- and a,ε-bis(7-bromonaphtho-3,4- quinon- 1-yldiphenylphosphonio) derivatives of butane and pentane

ortho-Quinones are widely spread in the nature and they attract rapt attention of researchers due to the versatile biological action (antitumor agents [1] and key intermediates in the processes of development of carcinomas [2], tuberculocidal drugs [3], pharmaceuticals for treating Shagas disease [4]). On the other hand, the ready formation of semiquinolate radicals makes these compounds promising for designing polymeric photosensitive materials [5]. ortho-Quinones as a rule are prepared by oxidation of the corresponding catechols with various oxidants like silver oxide [6], sodium periodate [7], lead dioxide [8], hydrogen peroxide [9]. In many cases for the synthesis of quinines containing other functional substituents milder oxidants should be applied. In this study we for the fi rst time have developed an effi cient procedure of the oxidation of bis-catechols linked through phosphonium groups by a polyalkylene chain into the corresponding ortho-quinones by treating with bromine. The oxidation of bis-phosphonium derivatives I, II proceeds under mild conditions at room temperature affording phosphorus-containing diquinones III, IV in nearly quantitative yelds. The completion of reaction was monitored by the IR spectroscopy following the disappearance of broad absorption bands of hydroxy groups in the region 3100–3300 cm–1 and the appearance of strong narrow absorption bands in the region 1682–1692 cm–1 corresponding to the ortho-quinone fragment. The formation of the ortho-quinone fragment is