Divergent Synthesis of Quinazolines Using Organocatalytic Domino Strategies under Aerobic Conditions

Abstract

An easy and efficient organocatalytic approach to the synthesis of 2-substituted quinazolines is described based on the reaction between 2-aminobenzylamines and aldehydes or alcohols or amines. Three organocatalytic platforms were investigated, using 3-nitropyridine, pyridine N-oxide, and vitamin B-3. Having established the new catalytic systems, the tandem transformations of 2-aminobenzylamines to give substituted quinazolines were achieved in excellent yields and with a broad substrate scope, with no formation of toxic side-products. The investigated conditions are not restricted to the use of aldehydes; the protocol also works well with alcohols or amines as substrates. These are oxidized in situ to the corresponding aldehydes to achieve the successful transformation. A mechanistic proposal has been drawn up based on control experiments. We found that under aerobic conditions, catalytic amounts of H2O2 can be generated; this plays a key role in the efficacy of the described approach. The green chemistry metrics of the developed method are also presented. The E factor of 8.18 mg/1 mg demonstrates that the reported method is an excellent complement to previous protocols.