Unexpected Annulation between 2-Aminobenzyl Alcohols and Benzaldehydes in the Presence of DMSO: Regioselective Synthesis of Substituted Quinolines

An unexpected annulation among 2-aminobenzyl alcohols, benzaldehydes, and DMSO to quinolines has been disclosed. For the reported annulation between 2-aminobenzyl alcohols and benzaldehydes, the change of the solvent from toluene to DMSO led to the change of the product from the diheteroatomic cyclic benzoxazines to monoheteroatomic cyclic quinolines. This annulation can be used to synthesize regioselectively different substituted quinolines by the choice of different 2-amino alcohols, aldehydes, and sulfoxides as substrates. Interestingly, introducing substituent groups to the alpha-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines. On the mechanism for this annulation was proposed.

Automated summary

An unexpected annulation reaction among 2-aminobenzyl alcohols, benzaldehydes, and DMSO has been discovered, leading to the synthesis of quinolines. By changing the solvent and substituents on substrates, regioselectively different substituted quinolines can be obtained. The proposed mechanism for this annulation reaction involves the interchange of positions between benzaldehydes and sulfoxides in the product quinolines.