Facile Syntheses of 1,8-Bis(diphenylphosphino)anthracene and 1,8-Bis(dimethylamino)anthracene by Nucleophilic Substitution of 1,8-Difluoroanthracene

Abstract

1,8-Bis(diphenylphosphino)anthracene (1) was prepared in a three-step synthesis in 51 % overall yield starting from 1,8-dichloro-9,10-anthraquinone (8). Compound 8 was converted by chlorinefluorine exchange and reduction with zinc into 1,8-difluoroanthracene (7) from which 1 was obtained by reaction with potassium diphenylphosphide. The conversion of 7 with lithium dimethylamide to 1,8-bis(dimethylamino)anthracene (10) clearly showed that in the case of 7 direct nucleophilic displacement (addition-elimination mechanism) dominates over aryne formation (elimination-addition mechanism). Single crystal X-ray structure analyses are reported for 1 and 10. Previouslywe reported the synthesis of the 1,8-bis(diphenylphosphino)anthracene (1) and its reaction with nickel or palladium dichloride forming cyclometallated and hence extremely stable complexes 2 and 3. 2 As a result of the cyclometallation at the anthracene C-9 atom, the diphosphine 1 is acting as a tridentate PCP ligand in these complexes. Whereas we first had failed to prepare the diphosphine 1 from either 1,8-dichloro-or 1,8-dibromoanthracene, 1 was obtained in moderate yield of 33 % by reaction of potassium anthracenedisulfonate (4) with two equivalents potassium diphenylphosphide (Ph 2 PK) in diethylene glycol diethyl ether (DEGDEE) under harsh reaction conditions (180°C, 20 h). 2,3 The disulfonate 4 needed for this conversion was prepared by zinc reduction of potassium 9,10-anthraquinone-1,8-disulfonate. 4 However, since the latter compound apparently is not commercially available anymore, it was desirable to search for a new and improved synthesis of the diphosphine 1.In a recent paper we described the reaction of 4,5-difluoroacridine (5) with potassium diphenylphosphide (Ph 2 PK) giving 4,5-bis(diphenylphosphino)acridine (6) in 79 % yield. 5 This prompted us to attempt the synthesis of 1 from 1,8-difluoroanthracene (7) and to investigate the use of fluoro substituted polycyclic aromatic hydrocarbons in nucleophilic aromatic substitution reactions with alkali metal phosphides and other nucleophiles. 6The unknown 1,8-difluoroanthracene (7) was prepared from the commercially available 1,8-dichloro-9,10-anthraquinone (8) in a twostep synthesis. Following a literature procedure 8 was converted by reaction with cesium fluoride in dimethyl sulfoxide under anhydrous conditions into 1,8-difluoro-9,10-anthraquinone (9) [m.p. = 228°C (DSC, lit. 7 m.p. = 228-229°C), 71 %]. 7 Reduction of 9 with zinc powder in aqueous ammonia (75°C, 4 h) followed by an acidic treatment (aqueous HCl, 2-propanol, reflux, 3 h) yielded 7 [yellow needles, m.p. = 142°C (DSC), 84%]. 8,9 As anticipated compound 7 proved to be highly reactive for nucleophilic displacement of the fluoro substituents by alkali metal phosphides. Reaction with two equivalents potassium diphenylphosphide (Ph 2 PK, dioxane/THF 5:1 reflux, 3 h) 10 converted 7 in excellent yield to the diphosphine 1 [yellow needles, m.p. = 234°C (lit. 2 m.p. = 233-235°C), 86 %]. For the three-step synthesis starting from commercial 8...

Palladium‐Catalyzed Electrophilic Substitution via Monoallylpalladium Intermediates

“…The reactions were performed with 4 a – c and various aldehydes 5 and imine 6 in the presence of catalytic amounts of 1 – 3 to obtain homoallylic alcohols 7 and amines 8 , respectively (Table 1). Complexes 1 a 4c and 2 a 5a,c showed high catalytic activity and very high stability under the reaction conditions. Although the reactions could be performed in many different solvents, the best results were obtained in DMF (for 1 a ) and THF (for 2 a ).…”

Synthesis of a Novel Potential Tridentate Anthracene Ligand, 1,8-Bis(dimethylamino)-9-bromoanthracene, and Its Application as Chelate Ligand for Synthesis of the Corresponding Boron and Palladium Compounds

“…To prepare 5 , we examined the possibility for direct lithiation of 1,8‐bis(dimethylamino)anthracene ( 3 )2 with various bases ( n BuLi, s BuLi, and t BuLi) in various solvents (diethyl ether, THF and hexane) with or without addition of TMEDA, but the lithiation at the 9‐position did not take place at all. In addition, a strategy to use 1,8‐bis(dimethylamino)anthrone as a synthetic intermediate that is based on our previous synthesis of 1,8‐dimethoxy‐9‐bromoanthracene,1b did not work because reduction of 1,8‐bis(dimethylamino)anthraquinone to the corresponding anthrone was not successful.…”

“…Recently, we reported synthesis of hypervalent pentacoordinate carbon compound bearing a rigid anthracene skeleton, which was prepared from 1,8‐dimethoxy‐9‐trifluoromethanesulfonyloxyanthracene,1a and of hypervalent pentacoordinate boron compounds ( 2 ) from 1,8‐dimethoxy‐9‐bromoanthracene ( 1 ) 1b. Although anthracene bearing only two dimethylamino groups at 1,8‐positions ( 3 ) has been synthesized in trace amounts by Haenel et al,2 compound 3 has not been used as a potential tridentate ligand, probably because of the inefficient synthetic method and inertness toward introduction of transition metal compounds. However, such a rigid tridentate anthracene ligand has eagerly been desired, since several bi‐3 and tridentate ligands bearing dimethylamino groups, especially van Koten type tridentate ligand such as 2,6‐bis(dimethylaminomethyl)phenyl ligand ( 4 ), have been effectively applied for stabilization of highly‐coordinated main‐group‐element compounds,4 and for transition‐metal catalysts of various reactions5 such as organoplatinum crystals for gas‐triggered switches 6…”

Thermally Stable Homogeneous Catalysts for Alkane Dehydrogenation S.O. thanks the German Academic Exchange Service (DAAD) for financing a research stay with W.C.K. in the USA. This work was supported by the National Science Foundation (CHE 9800184 to M.B.H.), by the University of California Energy Institute and University of California Santa Barbara (to W.C.K.), and by the German Research Association (DFG, to M.W.H). We thank Dr. R. Mynott and Mrs. C. Wirtz, MPI für Kohlenforschung, for NMR spectroscopic i

“…Anthraphos 9 was prepared similarly to 11 9b by direct nucleophilic substitution of 1,8‐difluoroanthracene with two equivalents of potassium di‐ tert ‐butylphosphide ( t Bu 2 PK, dioxane/THF 5/1, reflux, 1 h, 80 % yield) 10, 11. In analogy to the preparation of 2 5a the reaction of 9 and IrCl 3 ⋅3 H 2 O in 2‐propanol/water gave 14 (red crystal powder, m.p.…”