Palladium-catalyzed cycloaddition of alkynyl aryl ethers with isocyanates proceeds through o-C–H activation to afford 2-methylidene-2H-1,4-benzoxazin-3(4H)-one derivatives. Deuterium-labeling experiment shows that o-hydrogen is cleaved selectively and migrated to 2-methylidene moiety in the product. Various substrates are applied to this transformation to afford various substituted cycloadducts. 1,4-Bis(alkynoxy)benzenes can be used for the synthesis of multicondensed cycles to afford benzo[1,2-b:4,5-b′]bis[1,4]oxazine-3,8-dione derivatives.
钯催化的炔基芳醚与
异氰酸酯的环加成反应通过邻位C–H活化进行,生成2-甲基亚烯-
2H-1,4-苯并噁嗪-3(4H)-酮衍
生物。
氘标记实验表明,邻位氢选择性断裂并迁移到产物中的2-甲基亚烯部分。多种底物被应用于该转化,生成不同取代的环加成产物。1,4-双(炔氧基)苯可用于合成多缩合环,生成苯并[1,2-b:4,5-b′]双[1,4]噁嗪-3,8-二酮衍
生物。