Acetalization and thioacetalization of cabonyl compounds: A case study based on global and local electrophilicity descriptors

Acetalization of benzaldehyde and substituted benzaldehydes (containing both electron-donating and electron-withdrawing groups) is explained qualitatively on the basis of global electrophilicity descriptor, w, as proposed by Parr and coworkers (J Am Chem Soc 1999, 121, 1922). The generated values of w can explain qualitatively the preferential electrophilic addition, and hence, the yield of acetalization obtained in an earlier experimental study carried by Patel and coworkers (J Org Chem 2002, 67, 5842). The present study also reveals that although both steric and electronic factors affect the yield, only later can be taken care of by w. In the case of a competitive formation of cyclic acetals and cyclic thioacetals from a reaction mixture containing p-hydroxybenzaldehyde, p-nitrobenzaldehyde, 1,2-ethanediol (i.e., glycol), and 1,2-ethanedithiol, the relative experimental yields (Org Biomol Chem 2004, 2, 1670) could be explained from the difference of the global electrophilicity values between aldehydes and acetalizing agents in the same line of arguments of Maynard et al. (Proc Natl Acad Sci USA 1998, 95, 11578). (c) 2006 Wiley Periodicals, Inc.