Reaction of singlet oxygen with 2-pyrazoline: implication for cation radical - superoxide ion pair intermediate

Regioselective Synthesis of Polysubstituted Pyrazoles and Isoxazoles

“…Dihydropyrazoles (pyrazolines) 5a − e can be further converted to trisubstituted pyrazoles 8a − e by treatment with a mild base in 81−94% yields. The structures of 8a , 8b , 8c, 8d , and 8e 5 were assigned by comparison with their literature spectroscopic data.…”

“…Crystal data for 4d: C18H17N3O, MW 291.35, monoclinic, space group P21/c, a ) 17.387 (7), b ) 8.447(3), c ) 10.587(4) Å, β ) 100.016(5)°, V ) 1531(1) Å 3 , F(000) ) 616, Z ) 4, T ) -105 °C, µ (Mo KR) ) 0.081 mm -1 , Dcalcd ) 1.264 g cm -3 , 2θmax 53°(CCD area detector, Mo KR radiation), GOF ) 0.999, wR(F 2 ) ) 0.0997 (all 3097 data), R ) 0.0379 (2189 data with I > 2σI).…”

“…White needles from methanol (68%), mp 155-157 °C; 1 H NMR δ 8.06 (d, J ) 8.0 Hz, 1H), J ) 8.0 Hz,1H),4H),7H),6.65 (d,J ) 9.7 Hz, 1H), 4.61 (d, J ) 9.8 Hz, 1H), 3.08 (s, 3H), 2.35 (s, 3H); 13 C NMR δ 146. 7,142.8,138.5,134.2,131.5,130.7,129.8,128.6,127.8,126.9,124.9,124.2,120.3,110.1,76.5,72.8,40.9,21.1. Anal.…”

“…Oil (60%); 1 H NMR δ 7.28-7.19 (m, 10H), 6.34 (s, 1H), 3.10 (m, 1H), 1.35 (d, J ) 7.0 Hz, 6H); 13 C NMR δ 159. 7,143.2,140.1,130.8,128.7,128.5,128.2,127.8,126.8,125.0,104.7,27.8,22.8. Anal.…”