Selective reduction of 2-
[formula: see text] NaBH4 reduction of 2,5-bis[(4'-(n-alkoxy)benzoyl)oxy]benzaldehydes produces primarily the rearranged phenol, which does not generate liquid crystalline phases when laterally attached to a polymer backbone. Rearrangement is prevented by quenching the intermediate benzyl alkoxide with a weak acid. For example, 2,5-bis[(4'-(methoxy)benzoyl)oxy]benzaldehyde is selectively reduced to 2,5-bis[(4'-(methoxy)benzoyl)oxy]-benzyl alcohol with less than 5% intramolecular transesterification using 2-3 equiv of NaBH4 in the presence of 20-30 equiv of acetic acid (1:10 NaBH4/AcOH).
Pugh
C
Maurice Morton Institute of Polymer Science, University of Akron, Ohio 44325-3909, USA. cpugh@polymer.uakron.edu