M. Anteunis

Preparation of the four isomeric 2-trifluoromethyl-4-dimethylaminomethyl-1,3-dioxolan methiodides

Abstract The four isomers of the title compound have been prepared almost entirely optical pure, along five sequences starting from D-mannitol. Some new preparative steps, preventing optical loss have been developed. Diox(ol) an formation can easily been achieved with polyhalogenated carbonyl derivatives when the corresponding diol is used as its mono tosylate. Formation of dioxolan is exclusively preferred over dioxan formation if both systems during this reaction can be formed. Glycidol is shown to react stereospecifically with trifluoroacetaldehyde. It was possible to avoid racemisation completely during the substitution reaction of hydroxyl by chlorine (PΦ 3)/CCl 4 ) in the presence of a non-nucleophilic base. The 2-CF 3 -dioxolanic moiety on itself is incapable to complex with chiral LIS-reagents in order to induce diastereotopicity.

On the preparation of 2-halo alkyl substituted 1,3-dioxolanes and 1,3-dioxanes

Abstract Several methods for the preparation of 2-perfluoromethyl-substituted 1,3-dioxolanes and 1,3-dioxanes were tried. The method of Nerdel for the preparation of 1,3-dioxolanes, making use of the condensation between carbonyl compounds and oxiranes, was found to be suitable for perhalogenated ketones and aldehydes, and may even be extended to oxetanes, affording 2-perhaloalkylated 1,3-dioxanes. The yield of the cyclic acetals drops with inreasing substitution.

Preparation of the laevorotatory trans-(4S,6S)-4,6-dimethyl-1,3-dithiane and trans-(4S,6S)-4,6-dimethyl-1,3-oxathiane. An internal displacement of a secondary sulphonate leading to a cyclic thioacetal

Abstract (—)(2R,4R)-2,4-dimesyloxypentane, treated with (i) potassium thiolacetate/DMF (ii) 12N hydrogen chloride/dimethoxymethane/methanol yields (—)(4S,6S)-4,6-dimethyl-1,3-oxathiane and (—)(4S,6S)-4,6-dimethyl-1,3-dithiane. The mechanism of the formation of the oxathiane is discussed.

Oxidation products of hop bitter acids. Part VI. Five-membered ring products from the oxidation of colupulone

Oxidation of colupulone (I) produces a complex mixture, separation of which by counter-current distribution gives the cyclopenta[b]furan (III) and the cyclopenta[b]pyran (IV). Support for these structures comes mainly from n.m.r. and mass spectral data.