Cleare, Peter John Vernon (1968)
The formation and fission of cyclic acetals.
Full text access: Open
Acetal condensations of a number of aldehydes with D-glucitol in dilute aqueous and non-aqueous acid media havebeen followed polarimetrically. Those involving acetaldehyde, propionaldehyde, n- and iso-butyraidehyde and benzaldehyde apparently proceed via a kinetically controlled intermediate, with a comparatively large negative optical rotation, before attaining an equilibrium in which the 2,4-monoacetal is the major product. Similar behaviour has not been observed with either formaldehyde or trichloroacetaldehyde.For the reactions of D-glucitol with n-outyraldehyde and benzaldehyde the intermediate compounds have been isolated, characterized and shown to be the 2,3-0-outylidene and 2,3-0-oenzylidene-D-glucitols respectively, which were previously unknown Proton magnetic resonance (PMR) spectroscopic studies have been carried out on both compounds and these results, together with melting point and specific rotation data, indicated the 2,3-0-oenzylidene compound, as isolated, to be a mixture of diastereoisomers.Work on the hydrolyses of these two acetals suggested that they are considerably more labile than the corresponding 2,4-monoacetals. Moreover, 2,3-0-benzylidene-D-glucitol was hydrolysed much more rapidly than the butylidene compound. In non-aqueous media, both compounds underwent ring migrations in which the 2,4-monoacetals appeared to be the principal products. The reactions of n-butyraldehyde with various derivatives of D-glucitol in dilute aqueous acid have been studied in a similar manner, and four new acetals have been isolated and identified. 1-Deoxy-D-glucitol reacted in the same way as D-glucitol, forming 2,3-0-butylidene-1-deoxy-D-glucitol under kinetic control which subsequently passed to 2,4-O-butylidene-1-deoxy-D-glucitol. With 2-deoxy-D-glucitolf the kinetically controlled product was 1,3-0-butylidene-2-deoxy-D-glucitol.No kinetically controlled products could be observed with 3-0-methyl-D-glucitol but the main product appeared most likely to be 2,4-0-butylidene-3-0-methyl-D-glucitol.
This is a Accepted version
This version's date is:
is not peer reviewed
Deposited by () on
in Royal Holloway Research Online.Last modified on 01-Feb-2017
Digitised in partnership with ProQuest, 2015-2016.
Institution: University of London, Royal Holloway College (United Kingdom).