Advanced Catalytic Syntheses of 1,3-Oxazine Derivatives via Electrophilic Substitution Using Mono- and Bimetallic Phosphate Catalysts: Co₃(PO 4 ) 2 and CoCa 3 (HPO 4 )(PO 4 ) 2 (OH)

Abstract This research introduces a novel catalytic approach for the synthesis of 1,3-oxazinone derivatives through a multicomponent reaction that relies on an electrophilic substitution mechanism, employing two cobalt-based phosphate catalysts. This approach, allowed us to synthesize oxazine derivatives, known for their significant biological activities, achieving impressive yields of up to 97% in a remarkably short time of only 7 minutes, all under conditions environmentally friendly according to the principles of green chemistry using the ethanol/water mixture as a green solvent. In our study, we utilized two catalysts derived from cobalt-modified phosphate, which were synthesized in our laboratory using simple methods. The first support consists of a monometallic catalyst, denoted as Co₃(PO₄)₂, whereas the second is a bimetallic phosphate catalyst modified with cobalt and calcium CoCa₃(HPO₄)(PO₄)₂(OH). Our developed methods had various advantages including simplicity of the process, rapid reaction time, simple clean-up, ability to recover and reuse the catalyst and overall simplicity. All these advantages render this developed approach effective and viable for synthesizing oxazine derivatives suitable for large-scale applications.