A Convenient Synthesis of 9H-Thioxanthen-9-ones and Their Aza-Analogues

Abstract

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,

Tailoring Valence Tautomerism by Using Redox Potentials: Studies on Ferrocene‐Based Triarylmethylium Dyes with Electron‐Poor Fluorenylium and Thioxanthylium Acceptors

“…[ 20 , 21 , 22 ] The carbinol precursors 1 a ‐OH to 1 c ‐OH were synthesized from 4‐ferrocenylphenyl lithium and the respective fluorenone derivatives 6 a , 6 b [33] or the previously unknown 3,6‐bis(trifluoromethyl)‐9 H ‐thioxanthen‐9‐one, ( 5 ) according to Scheme 3 . Compound 5 was prepared by adopting Kobayashi's method [34] via a three‐step synthesis involving nucleophilic attack of the lithiated arene 2 a on benzaldehyde 2 b (see the cautionary note in the Experimental Section), oxidation with pyridinium chlorochromate (PCC), and nucleophilic substitution of the remaining F and Br substituents with simultaneous introduction of the thioether bridge using Na 2 S nonahydrate. Synthetic details and spectroscopic characterization of isolated intermediates can be found in the Experimental Section (see the Supporting Information).…”

4-Ferrocenylphenyl-Substituted Tritylium Dyes with Open and Interlinked C+Ar2Entities: Redox Behavior, Electrochromism, and a Quantitative Study of the Dimerization of Their Neutral Radicals

“…Complexes 1 + – 7 + were synthesized by two-step procedures involving the nucleophilic addition of 4-ferrocenylphenyllithium to the respective ketone and subsequent protolytic dehydration of the resulting carbinols 1-OH – 7-OH with Brookhart’s acid [H­(OEt 2 ) 2 ] + [B­{C 6 H 3 (CF 3 ) 2 -3,5} 4 ] − , which is subsequently denoted as BAr F 24 – . The required ketones were either obtained from commercial sources or prepared according to literature-known procedures. − 3,6-Dimethyl-9 H -thioxanthen-9-one ( 10 ) was prepared in a three-step synthesis in a manner largely analogous to that for similar thioxanthen-9-one derivatives, as detailed in the Experimental Section …”

“…42−44 3,6-Dimethyl-9H-thioxanthen-9-one (10) was prepared in a three-step synthesis in a manner largely analogous to that for similar thioxanthen-9-one derivatives, as detailed in the Experimental Section. 45 Carbinols 1-OH−7-OH were obtained as orange solids in yields of 43−98% and characterized by NMR spectroscopy and Scheme 2. Jacobsen−Nauta Structure of the Trityl Dimer (Left) 26 and Hexaphenylethane-Type Structures of Binaphthyl-Clamped Xanthyl Radicals (Middle) 34 In the case of the (dihydro)dibenzo[a,d]cyclo-heptatrienylium derivatives 1-OH and 2-OH, single crystals suitable for Xray crystallography were obtained.…”

“…3,6-Dimethyl-10-thioxanthen-9-one ( 10 ) was prepared according to a four-step procedure adapted from the literature as described in detail in the Supporting Information (for NMR characterization see Figures S79 and S80). For a batch size of 0.52 mmol, a yield of 214 mg (0.47 mmol, 82%) was obtained. 1 H NMR (CD 2 Cl 2 , 400 MHz): δ (ppm) 7.88 (d, 3 J HH = 8.0 Hz, 2H, H-11), 7.27 (d, 3 J HH = 8.7 Hz, 2H, H-7), 7.26–7.24 (m, 2H, H-14), 7.22–7.18 (m, 2H, H-12), 6.91 (d, 3 J HH = 8.7 Hz, 2H, H-6), 4.54 (vt, 2H, H-2), 4.26 (vt, 2H, H-1), 3.98 (s, 5H, H-4), 2.84 (br s, 1H, OH-17), 2.37 (s, 6H, H-16).…”

Fused Systems Based on 2‐Aminopyrimidines: Synthesis Combining Deprotolithiation‐in situ Zincation with N‐Arylation Reactions and Biological Properties

“…1‐Azaxanthone ( 1d ), 1‐azathioxanthone ( 1e ), 1‐azafluorenone ( 1f ), 3‐benzoyl‐2‐fluoropyridine ( 1j ), 3‐benzoyl‐2‐chloropyridine ( 1k ), 2‐chloro‐3‐(2‐chlorobenzoyl)pyridine ( 1l ), 2‐chloro‐3‐(2‐methoxybenzoyl)pyridine ( 1m ), 2‐chloro‐3‐cinnamoylpyridine ( 1n ), 3‐benzoyl‐2‐methoxypyridine ( 1o ), and ZnCl 2 · TMEDA were prepared as described previously.…”