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Synthesis of 4H-1,3-benzoxazines

Recent Literature

Unprecedented catalyst-controlled divergent cyclizations of Morita-Baylis-Hillman carbonates provide 1,2-dihydroquinolines in the presence of Cs2CO3 or 4H-3,1-benzoxazines in the presence of quinuclidine.
W. Cai, Y. He, Y. Zhou, Y. Huang, J. Org. Chem., 2021, 86, 12267-12276.

Treatment of various 2-amino-arylalkyl alcohols with isothiocyanates afforded thiourea intermediates, which were reacted in situ with molecular iodine in the presence of triethylamine to give 2-amino-4H-1,3-benzoxazines. The reaction of the thiourea intermediates with T3P as mild cyclodehydrating reagent and triethylamine as the base provides 2-amino-4H-1,3-benzothiazines.
V. P. R. K. Putta, N. Vodnala, R. Gujjarappa, U. Tyagi, A. Garg, S. Gupta, P. P. Pujar, C. C. Malakar, J. Org. Chem., 2020, 85, 380-396.