Sulfamic Acid: A Very Useful Catalyst

Abstract

Sulfamic Acid (NH2SO3H, SA) is a dry, nonvolatile, non-hygroscopic, odorless, uncorrodible crystalline solid with outstanding physical stability. It has been determined that SA is comprised not of the aminosulfonic acid form, but rather of +H3N-SO3 - zwitterionic units by both X-ray and neutron diffraction techniques. [1] It dissolves moderately in water, and can be highly ionized to form strongly acidic solutions. Sulfamic acid is immiscible with commonly used non-polar organic solvents, such as toluene and THF. It is commercially available and is inexpensive. Recently, SA emerged as a promising solid-acid catalyst for acid-catalyzed reactions, such as functional group protections and deprotections, [2-4] and the synthesis of isoamyl acetate [5] and polymeric ethers. [6] Moreover, some important organic transformations, including Beckmann rearrangement, [7] ­inter- and intramolecular imino Diels-Alder reactions, [8] and Pechmann [9] and Biginelli condensations, [10] [11] have also been performed successfully in the presence of sulfamic acid.