Efficient acetalisation of aldehydes catalyzed by titanium tetrachloride in a basic medium

The acetalisation of aliphatic and aromatic aldehydes is achieved in a basic medium by using catalytic amount of Ti(IV) chloride in MeOH in the presence of NH3 or Et3N. The present protocol shows many advantages over the well known base or acid catalysis: in fact, in contrast to base-promoted acetalisation, aldehydes with electron-rich carbonyl groups react easily, enolizable aldehydes do not undergo aldol condensation and, in contrast to acid-catalysis, migration of the double bond does not occur in the preparation of α, β-unsaturated acetals.Download : Download full-size image