Straightforward Access to 3,4-Dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides and Quinazolines via Iron-Catalyzed Aerobic Oxidative Condensation of Amines

A novel and straightforward approach for constructing 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides from 2-aminobenzenesulfonamide and benzylamines via oxidative condensation has been explored. Abundant and cheap iron salt as a catalyst and air as an oxidant were employed, which makes the process more practical and economical. This reaction protocol was further applied to synthesize diverse functionalized quinazolines through oxidative condensation of 2-aminobenzylamines with benzylamines. Besides this, the use of amino acid such as phenylglycine as benzylamine surrogate has also been tested for the construction of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide and quinazoline derivatives. The proposed mechanistic pathway has been validated by isolating the key intermediates.