Categories: C-O Bond Formation, Synthesis of O-Heterocycles >

Synthesis of acetals

Name Reactions

Protecting Groups

Cyclic Acetals

Tetrahydropyranyl Ethers

Recent Literature

Perchloric acid adsorbed on silica gel is an extremely efficient, inexpensive, and reusable catalyst for the protection of aldehydes and ketones and the subsequent deprotection. Acetalization was mostly carried out under solvent-free conditions with trialkyl orthoformates, but weakly electrophilic carbonyl compounds and substrates that can coordinate with the catalyst, required the corresponding alcohol as solvent.
R. Kumar, D. Kumar, A. K. Chakraborti, Synthesis, 2007, 299-303.

Zirconium tetrachloride (ZrCl₄) is a highly efficient and chemoselective catalyst for the acetalization, and in situ transacetalization of carbonyl compounds under mild reaction conditions.
H. Firouzabadi, N. Iranpoor, B. Karimi, Synlett, 1999, 321-323.

0.01 mol-% Zinc(II) salts catalyze the reaction between acetals and acid halides to provide haloalkyl ethers in near-quantitative yield in 1 - 4 h. The solutions of haloalkyl ethers can be utilized directly in reactions in which the presence of the ester byproduct does not interfere. Excess carcinogenic haloalkyl ether is destroyed on workup.
M. A. Berliner, K. Belecki, J. Org. Chem., 2005, 70, 9618-9621.

Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide in absolute alcohol. This convenient, mild, chemoselective method allows acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, and tolerates acid-sensitive protecting groups.
R. Gopinath, Sk. J. Haque, B. K. Patel, J. Org. Chem., 2002, 67, 5842-5845.

An intramolecular hydro-O-alkylation of aldehydes leads to spiroketals, bicyclic ketals, and aminals. Tertiary and sterically hindered secondary sp³ C-H bonds are transformed into C-O bonds under the action of a catalytic amount of a variety of Lewis acids. The mechanism probably involves a tandem hydride transfer/cyclization sequence.
S. J. Pastine, D. Sames, Org. Lett., 2005, 7, 5429-5431.

A mild, gold- and brønstedt acid-catalyzed tandem cycloisomerization-hydroalkoxylation of various homopropargylic alcohols in the presence of an alcohol provides an efficient route to tetrahydrofuranyl ethers.
V. Belting, N. Krause, Org. Lett., 2006, 8, 4489-4492.