An efficient method for the preparation of 9H-thioxanthen-9-ones and their three aza-analogues has been developed. The reaction of (2-fluorophenyl)(2halophenyl)methanones, derived from 1-bromo-2-fluorobenzenes and 2halobenzaldehydes by an easy two-step sequence, with Na 2 S·9H 2 O in DMF at 60 ˚C gives 9H-thioxanthen-9-ones. This procedure can be applied to the synthesis of 5H-[1]benzothiopyrano[2,3-b](or [2,3-c])pyridin-5-ones or 10H-[1]benzothiopyrano[3,2-c]pyridin-10-ones starting from 2-, 3-or 4-chloropyridines,respectively. INTRODUCTIONA literature survey of the utility of 9H-thioxanthen-9-one derivatives indicated that a number of compounds having this skeleton exhibit a variety of biological activities, 1 and that some compounds are useful for photosensitive materials. 2 While 9H-thioxanthen-9-ones have been commonly prepared by the intramolecular Friedel-Crafts acylation of 2-(arylsulfanyl)benzoic acids under harsh conditions, 2,3 few other general methods have been developed. We envisioned that the reaction of (2-fluorophenyl)(2halophenyl)methanones, which have been easily prepared from 1-bromo-2-fluorobenzenes and 2-halobenzaldehydes and used for the preparation of 10-substituted acridin-9(10H)-ones, 4 with Na 2 S·9H 2 O under mild conditions would provide 9H-thioxanthen-9-ones. 5 In this paper, we wish to describe the results of our investigation, which show that 9H-thioxanthen-9-ones (2) can be prepared by the reaction of (2-fluorophenyl)(2-halophenyl)methanones (1) with Na 2 S·9H 2 O in DMF at 60 °C.We also report that this method is applicable to the synthesis of three types of their aza-analogues,

The reaction of 1-fluoro-2-lithiobenzenes, generated from 1-bromo-2-fluorobenzenes 1 and BuLi, with 2-halobenzaldehydes and subsequent oxidation of the resulting alcohols 2 afforded (2-fluorophenyl)(2-halophenyl)methanones 3, which, on treatment with benzenamines or arylmethanamines, followed by NaH, gave rise efficiently to 10-aryl-or 10-(arylmethyl)acridin-9(10H)-ones (5 or 7), respectively.Introduction. -Acridin-9(10H)-one derivatives have attracted much attention of not only medicinal but also synthetic chemists, because a number of molecules with this heterocyclic skeleton have been reported to exhibit a variety of biological activities [1] [2], and some have been isolated from nature [3]. The acridin-9(10H)-one structure has been constructed by intramolecular FriedelÀCrafts acylation of 2-(arylamino)benzoic acids with appropriate acid catalysts under harsh conditions [2] [4], while several direct methods for the synthesis of 10-substituted acridin-9(10H)-ones have recently reported by several groups [5]. In this article, we describe a new method for the preparation of 10-substituted acridin-9(10H)-ones starting with 1-bromo-2-fluorobenzenes 1 and 2-halobenzaldehydes. We found that 10-aryl-and 10-(arylmethyl)acridin-9(10H)-ones, 5 and 7, respectively, which are rather difficult to prepare by previously described methods [2] [4] [5], can be obtained by the substitution reaction of (2fluorophenyl)(2-halophenyl)methanones 3, derived by an easy two-step sequence from these starting materials, with benzenamines and arylmethanamines, followed by cyclization of the resulting intermediates 4 and 6, respectively, by treatment with NaH. After completion of this work, a similar approach, which allows the synthesis of fluorinated acridin-9(10H)-ones by the reaction of highly fluorinated benzophenones with primary amines under heating, has been reported as a special case [5d].Results and Discussion. -The key precursors, (2-fluorophenyl)(2-halophenyl)methanones 3, were prepared as outlined in Scheme 1. 1-Bromo-2-fluorobenzenes 1 were treated with BuLi in Et 2 O at À 788 to generate 1-fluoro-2-lithiobenzenes, which were allowed to react with 2-halobenzaldehydes to give (2-fluorophenyl)(2-halophenyl)methanols 2. These were oxidized with pyridinium chlorochomates (PCC) in CH 2 Cl 2 at room temperature to give 3 in satisfactory yields.

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