Efficient synthesis of naphtho[1,2-e][1,3]oxazine derivatives via a chemoselective reaction with the aid of low-valent titanium reagent.

A series of new naphtho[1,2-e][1,3]oxazine derivatives such as trans-1,3-diaryl-1H-naphtho[1,2-e][1,3]oxazine-2(3H)-carbonyl chloride, 1-aryl-2-benzyl-1,2- dihydronaphtho[1,2-e][1,3]oxazine-3-one, and trans-1,3-diaryl-1H-naphtho[1,2-e] [1,3]oxazine-2(3H)-carbaldehyde were selectively synthesized via a chemoselective reaction of 1,3-diaryl-2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazines and triphosgene or triethyl orthoformate, respectively, induced by different low-valent titanium systems. This method has the advantages of short reaction time (15 min), convenient manipulation, and high chemoselectivity.