Die Geschichte einer Acetalisierung und die überraschende Dimerisierung eines 1,3-Dioxan-4-ons zu einem Zwölfring [2-(tert-Butyl)6-(trifluoromethyl)-1,3-dioxan-4-on und 2,8-Di(tert-butyl)-6,12-bis(trifluoromethyl)-1,3,7,9-tetraoxacyclodecan-4,10-dion aus rac-,(R)- und (S)-4,4,4-Trifluoro-3-hydroxy-butansäure und Pivalaldehyd]

Abstract

All possible forms of 2-(tert-butyl)-6-(trifluoromethyl)-1,3-dioxan-4-one (rac, dextro- and laevoratatory of cis- and trans-isomer 2,3) are prepared and fully characterized. It is shown by DSC measurements that the racemic mixtures of both diastereoisomeric dioxanones crystallize as racemates and not as conglomerates. Preparation of the dioxanone, of which the cis-isomer 2 is thermodynamically favoured, from pivalaldehyde and trifluoro-hydroxy-butanoic acid is more straight-forward with the enantiomerically pure acid than with the racemic one: a poorly soluble, high-melting dimer 4 with a twelve-membered-ring structure, containing an (R)- and an (S)-molecule (Ci symmetry), is readily formed, even in the solid state, under the influence of traces of acid.