Process for preparing of 2,2'-dimethyl-1, 1'-binaphthalene and 2,7'-Dimethyl-1,1'binaphthalene

摘要

The prodn. of 2,2'-dimethyl-1,1'-binaphthyl (I) and 2,7'-dimethyl-1,1'-binaphthyl (II) comprises the electrochemical oxidative dimerisation of 2-methylnaphthalene (III) in acetonitrile/water/conductive salt mixts. contg. other component(s) (IV) which is/are immiscible or only partly miscible with water, followed by fractionation under vacuum. Also claimed is 2,7'-dimethyl-1,1'-binaphthyl (II). Water-immiscible component (IV) comprises (cyclo)aliphatic, aromatic or halogenated hydrocarbon, ketone or a mixt. thereof, esp. e.g., pentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, iso-octane, decane, dodecane or decalin, pref. 6-10C (cyclo)aliphatic hydrocarbon, esp. pref. heptane or octane, or benzene, toluene, xylene(s), mesitylene, naphthalene or tetralin, pref. 6-10C aromatic hydrocarbon, esp. pref. toluene or xylene, or CH2Cl2 or chlorobenzene, or a 5-10C ketone, pref. Et-CO-Et-, Me-CO-tert.-Bu or acetophenone. Or (III) itself may be used as component (IV), in amts. such that the electrolyte always contains 10-50 (pref. 15-40) wt.% (III). Suitable conductive salts are alkali, alkaline earth, ammonium or mono-, di-, tri- or tetra-alkylammonium salts of acids with anions derived from S(IV), P(V) or B(III), pref., e.g., hydrogen sulphate, methylsulphate, octanesulphonate, toluenesulphonate, methanephosphonate, hexafluorophosphate or tetrafluoro-borate (21 anions listed). Pref., salts are salts of opt. poly- or per-fluorinated alkane-sulphonic or -phosphonic acids, e.g., trifluoromethanesulphonate, nonafluoro-butanesulphonate or phosphonate, etc. (7 anions listed), or Na or tetra-(1-4C alkyl)-ammonium salts of 1-8C alkane-sulphonic acids, 1-4C poly- or per-fluoroalkane-sulphonic acids, arylsulphonic acids (with aryl = Ph, naphthyl, or alkyl- or Cl-substd. Ph), tetrafluoroboric acid or hexafluoro-phosphoric acid. Wt. ratio acetonitrile:water = (100:1)-(1:1), pref. (20:1)-(2:1); the electrolyte contains 10-90 (pref. 20-80) wt.% (IV) and 0.5-15 (pref. 1-7) wt.% conductive salt. Electrolysis is carried out at 0-80 (pref. 20-50) degrees C, with a current density of 10-250 (pref. 25-150, esp. pref. 40-100) mA/cm2, using an anode of graphite, vitreous carbon, Pt or stainless steel, pref. graphite, and a cathode of graphite, vitreous carbon or metal, pref. graphite or vitreous carbon. Rectification is carried out at up to 400 (pref. up to 350) degrees C and 5-100 (pref. 10-80, esp. pref. 10-60) hPa (column head pressure), with 30-90 (pref. 40-80, esp. pref. 50-70) sepn. stages and a reflux ratio of 3-60.