Nafion-H SAC-13 solid superacid is shown to exhibit outstanding properties as catalyst in the formation of various protective groups. These include the formation of tetrahydropyranyl ethers of alcohols and the removal of this protective group, acetalization of carbonyl compounds with ethane-1,2-diol and propane-1,3-diol, and the transformation of aldehydes to 1,1-diacetates. Products are isolated in good to excellent yields and the catalyst can be reused with practically no loss of activity. (c) 2004 Elsevier B.V. All rights reserved.