Abstract
The synthesis of a series of novel tricyclic O,N‐heterocycles 7a–k, a kind of unprecedented 2‐oxo‐[1,2,4]triazolo[3,2‐d][1,5]benzoxazepine derivatives, has been accomplished, featuring acid‐induced ring closure of the geminal arylazo isocyanato compounds 5, which were prepared from chroman‐4‐ones in three steps, followed by feasible ring expansion and basic work‐up.
Acknowledgments
We gratefully acknowledge financial support for this work from the National Natural Science Foundation of China through grant 20372015 and the Key Organic Synthesis Laboratory of Jiangsu Province (KJS01016).
Notes
a Crystal data for 7a. C16H13N3O2, M = 279.30, a = 8.929(3), b = 18.817(7), c = 7.923(3) Å, U = 1331.2(8) Å3, space group Pna21, Z = 4, T = 298(2) K, ρcalc = 1.394 g cm−3, μ = 0.09 mm−1, 6249 reflections were measured, 2562 unique which were used in all least square calculations, R 1(F) = 0.0220 (for 238 reflections with F 0 2 ≥ 2σ(F0 2), ωR 2(F2) = 0.0869 for all unique reflections.