“…1 H NMR (400 MHz, CDCl 3 , 293 K): δ =6.56–6.51 (m, 2 H, vinyl‐CH), 5.39–5.34 (m, 2 H, bridgehead CH), 2.07–2.00 (m, 1 H, bridge‐CH 2 ), 1.92–1.85 (m, 1 H, bridge‐CH 2 ), 1.67–1.60 (m, 1 H, bridge‐CH 2 ), 1.55–1.49 ppm (br t, 1 H, bridge‐CH 2 ); 13 C NMR (100 MHz, CDCl 3 , 293 K): δ =132.0, 128.6, 74.0, 60.3, 23.4, 21.7 ppm; FTIR (ATR): $\tilde \nu $ =1496 cm −1 (N‐ N ‐O); HRMS (ESI): m / z : calcd for C 6 H 8 N 2 O: 163.0268 [ M +K + ], 147.0529 [ M +Na + ], 125.0709 [ M +H + ], 249.1346 [ M 2 +H + ], 271.1165 [ M 2 +Na + ]; found: 163.0275, 147.0526, 125.0718, 249.1362, 271.1163. 1 H NMR chemical shift ranges30b,e, 47 and 13 C NMR30c data agree with those in the literature.…”