A Mild Protection of Ketones and Aldehydes as 1,3-Dioxolanes in the Presence of Benzenesulfohydroxamic Acid

Hassner et al. have reported a mild protection of ketones and aldehydes as 1,3-dioxolanes in the presence of benzenesulfohydroxamic acid (0.7 eq.). The reaction proceeds within ten minutes at room temperature in the absence of strong acids as a catalyst, and in the presence of base (Et₃N; 1 eq.). Acid-sensitive groups such as O-THP, N-Boc, O-TBS (t-butyldimethylsilyl), or O-TBDPS (t-butyldiphenylsilyl) are unaffected under the basic conditions. Thus, this synthetic method can be used complementary to other acid catalyzed acetalizations.