Fused Heterocycles containing One Oxygen or Sulphur Atom

4 Fused Heterocycles containing One Oxygen or Sulphur Atom 

spectra of a number of 2-substituted 4-chromanols and l-thio-4-chromanols in DMSO show that the OH proton resonates at higher field when it is pseudo-axial than when pseudo-equatorial its coupling constant with CH is lower in the pseudo-axial than in the pseudo-equatorial position. The observations may be explained in terms of conformational equilibria of the C—O bond. Dianin s compound (116 = Me, R = OH) forms clathrates with 

A Mannich reaction on 2,2-dimethylnaphtho[l,2- ]pyran-6-ol (117) gave the 5-aminomethyl derivative. Catalytic reduction of this gave the 5-methyl compound. In an attempt to chloromethylate the chroman (117), the spiran (118) was obtained in 78% yield.  

Reduced benzo[l,2-6 5,4-f ]dipyrans such as (119), when treated with 3-chloroperbenzoic acid at 15—20 °C, give macrocyclic lactones (120).  

Tocopherols and the mechanism of their anti-oxidant properties continue to interest chemists. Potassium superoxide, in the presence of dicyclohexyl-18-crown-6, converts the model compound 2,2,5,7,8-pentamethylchroman-6-ol (121) into its 4a,5 7,8-diepoxide (122). Benzoyl peroxide and the peroxides which are present in sunflower oil oxidize a-tocopherol to the phenoxyl radical, according to evidence obtained by e.s.r. and i.r. spectroscopy. In another study, (-l-)-5-tocopherol was oxidized, above 180 C, in various fats to the dimers (123) and (124). The effects of temperature and the nature of the triglyceride on the relative amounts of the two dimers were studied. 

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