Methods for Interconverting Aldehydes and Acetals

The conversion of an aldehyde (or ketone) to the corresponding acetal (or ketal) is not generally an obstacle in synthetic sequences. However some olefinic aldehydes undergo cyclization readily in the presence of mineral or Lewis acids (I, as an example),1 and in these cases (and for other extremely acid sensitive aldehydes) another method appeared desirable. We present here such an alternative, which may be of even more general applicability because of the high yields obtained and the short reaction times required.