Synthesis Of Benzoxazinones Via Domino C-H Amination By Rhodium

Benzoxazinones are one of important and widely used structural motifs in natural products,drugs,and biologically active compounds.Generally,traditional methods for the preparation of benzoxazinones mainly involve 1)intermolecular cyclization of anthranilic acids;2)palladium-catalyzed carbonylative reactions of N-(o-haloaryl)amides in the presence of CO or its surrogates such as paraformaldehyde,phenylformate,and oxalyl chloride;3)intramolecular cyclization of complex molecules.Although these reactions show better universality and attractiveness,most of them employ comparatively less available starting materials or involve multistep procedures or harsh reaction conditions.Thus,in the view of atomic economy and green chemistry,it is highly desirable to further develop convenient and efficient route to benzoxazinones from simple starting materials.Herein,a Rh(Ⅲ)-catalyzed [3+3] cycloaddition and C-H amidation from easily available N,N-dimethylbenzamide with 1,4,2-dioxazol-5-ones was developed,which offers a novel approach to benzoxazinones without external oxidant.Notably,this domino process involves the “one-pot” C-N and C-O bond constructions,and the subsequent C-H amination reaction without any other catalysts results as a consequence of the 2-phenyl-4H-benzo[d][1,3]oxazin-4-one formed in the previous step.The duomino reaction is effective because several synthetic transformations and multibond-forming steps can be carried out in a single pot,while circumventing several processes for purification of various precursors and tedious steps of protection and deprotection of functional groups at the same time,which could have widely potential applications in synthetic chemistry.