Cyclic acetals and ketals and their preparation

The invention comprises 5,5-dimethyl-2-propyl-1, 3-dioxan and a general process for making cyclic acetals and ketals by heating a glycol with an aldehyde or ketone in the presence of a catalyst comprising one or more of the metals rhodium, iridium, palladium or platinum on a carbon support. Specified glycols include 1,2-, 1,3- and 1,4-aliphatic and alicyclic glycols, which may bear substituent groups, e.g. alkoxy and aryl radicals. Specified aldehydes and ketones include the aliphatic and aromatic carbonyl compounds and those bearing halogens and hydroxy substituents. 2-(51,51-Dialkyl - 11,31 - dioxan - 21 - yl) - 2,2 - dialkylethanols can be made by heating 2,2-dialkylpropane-1 3-diol with a 2,2-dialkyl-3-hydroxypropan-1-al in the presence of the above catalysts, the 2,2-dialkyl-3-hydroxypropan-1-al being prepared in situ by heating the 2,2-dialkylpropane-1,3-diol in the presence of said catalysts. The process can be effected at normal or superatmospheric pressure, preferably at temperatures of 50-250 DEG C. and optionally in the presence of a solvent. Examples relate to the preparation of 5,5 - dimethyl - 2 - propyl - 1,3 - dioxan, 2 - tribromomethyl - 1,3 - dioxolan, cyclohexane - spiro - 21 - (11, 31 - dioxolan), and 2 - (51, 51 - dimethyl - 11, 31 - dioxan - 21 - yl) - 2 - methylpropan-1-ol.