N‐alkyl imidazole‐based homonuclear coordination complex as a neutral organocatalyst for the faster and efficient construction of 3,4‐dihydro‐2H‐1,3‐oxazine scaffold

Abstract

In the present work, homonuclear coordination complex including Zn (II) and N-hexadecylimidazole ligand was used for the first time as a highly efficient homogeneous neutral organocatalyst for the synthesis of 3,4-dihydro-2H-1, 3-benzoxazine monomers. Therefore, N-alkyl or N-aryl substituted, both mono-benzoxazine and bis-benzoxazine, were successfully synthesized (21 examples) via Mannich-type condensation reactions. Effortlessly obtaining the pure product with high yields and the short reaction time makes this method more useful and advantageous than the common existing benzoxazine synthesis methods.

Visible-light-catalyzed synthesis of 1,3-benzoxazines via formal [4 + 2] cycloaddition of oximes with o-hydroxybenzyl alcohols

“…Currently, their synthesis is achieved through a Mannich-type condensation of phenols with primary amines and two equivalents of formaldehyde (Scheme 1, (a)), 6 and condensations of secondary alkyl or arylamines that bear a naphthol or phenol moiety with formaldehyde (Scheme 1, (b)). 7 These two synthetic approaches are based on three-component and two-component Mannich-type condensation reactions, traditionally. However, there are still some disadvantages of the Mannich-type condensation reactions, such as long condensation time, high temperatures and low product yields.…”