Brønsted acid - catalyzed organic reactions

Abstract

Although Metal (ion) catalysis undoubtedly has been the most vibrant area of research in synthetic organic chemistry over the past two decades, Lewis acid catalyst is very often required over stoichiometric amounts of the “catalyst” because the product still contains a basic moiety that binds the Lewis acid. We synthesized several (thio)urea based and phosphoric acid based catalysts. Catalytic amounts (5 mol%) of bis-arylsulfonylurea promoted the Friedel-Crafts alkylation with nitroolefin and 1-methylindole. A sizeable improvement of the yield noticed on running the reaction in Toluene at room temperature. We also examined the catalytic ability of bis-arylsulfonylurea in Diels-Alder reaction. The bis-arylsulfonylurea catalyst under investigation show catalytic behavior (85% yields) and increase the stereoselectivity, even at a catalytic loading of only 1 mol%. Several chiral sulfonyl (thio)ureas and chiral phosphoric acids were prepared and applied to asymmetric reactions such as the Michael reactions, Mannich reaction and Diels-Alder reactions. But enontioselectivities were not observed.