Table I isolated substrate product yield,0 % 12 °All compounds were characterized by comparison of their physical and spectral properties with literature values.we have adopted is a modified two-phase Jones oxidation procedure (ether/aqueous chromic acid) which enables us to routinely prepare 3(H50 g of alkyl quiñones in a one-pot reaction. Although the yields obtained range from modest to very good (see Table I), the process itself is quite simple to carry out and far less expensive than the previously discussed procedures. The bonus associated with this method is that quiñones of reasonably high purity are virtually always obtained by simple extraction procedures; i.e., chromatographic purifications are rarely required.This method does not work well with 2-methoxyphenol, presumably due to competitive o-quinone formation and subsequent polymerization. Experimental SectionGeneral Methods. Melting points were determined with a Thomas-Hoover Uni-Melt capillary melting point apparatus. Infrared spectra were determined with Perkin-Elmer Model 257, 457, and 727 spectrophotometers. Nuclear magnetic resonance spectra were recorded by using Varían T-60, EM-360, and EM-390 spectrometers, and chemical shifts are reported in parts per million (8) relative to an internal tetramethylsilane reference. Nominal mass spectra were recorded by using a Finnigan 4000 GC/MS system and a Varían Associates M-66 spectrometer.General Procedure for the Conversion of Phenols to Quinones. This procedure will be illustrated by using 2,6-dimethylphenol. The other phenol oxidations listed in Table I can be accomplished by using exactly the same procedure. 2,6-Dimethylphenol (30 g, 0.25 mol) was dissolved in 350 mL of ether 0022-3263/83/1948-2933$01.50/0 and placed in a 2-L round-bottomed flask fitted with an overhead stirrer and an addition funnel. The reaction vessel was immersed in an ice-water bath, and the addition funnel was charged with Jones reagent, produced from Na2Cr207-2H20 (165 g, 0.5534 mol), 105 mL of 96% H2S04, and 235 mL of H20. Addition required approximately 2.5 h. After the addition, the reaction mixture was allowed to stir for at least 24 h. The reaction mixture was washed with ether (4 X 200 mL), and the combined ether extracts were washed with saturated NaHC03 solution (2 X 100 mL) and with water (200 mL). The ether layer was dried over MgS04 and concentrated in vacuo to yield 2,6-dimethylbenzoquinone: 28.1 g (84%); mp 44-46 °C (lit. mp 45-47 °C); NMR (CDC13) 6.55 (s, 2), 2.00 (s, 6); mass spectrum, m/e 136.
Aktivierte Chlorbenzole (I) können mit Hexamethyl‐phosphorsäuretriamid glatt zu den entsprechenden Dimethylanilinen (III) substituiert werden.
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