Sodium Sulfite → 1-Acetyl-3-(2,5-difluorophenyl)-5-phenyl-5-vinyl-4,5-dihydro-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

To a solution of 3.96 g (12.0 mmol) 1-3 in 200 mL CH2Cl2 was added 5.6 g (13.2 mmol) Dess-Martin Periodinane and the mixture was stirred for 3 h. To this was then added a saturated aqueous solution of NaHCO3 and also some solid Na2SO3, and the biphasic mixture was stirred vigorously for 1 h. The layers were separated, the organic was washed with saturated NaHCO3, water, dried over Na2SO4 and concentrated to provide the crude aldehyde. In a separate flask, 6.4 g (18.0 mmol) methyl triphenylphosphonium bromide was suspended in 100 mL of THF, cooled to −78° C., and 7.2 mL (18.0 mmol) 2.5M nBuLi in hexanes was added. After stirring for 30 min, the above aldehyde dissolved in 30 mL of THF was cannulated into the reaction flask and stirring was continued for 30 min at −78° C. The cooling bath was removed and the reaction was allowed to stir for 1 h while coming to room temperature. The reaction was quenched with saturated aqueous NH4Cl, the mixture was dumped into a separatory funnel with EtOAc, the layers were separated, the aqueous layer was extracted with EtOAc, the combined organics were washed with brine, dried over Na2SO4, and concentrated. The residue was purified by silica gel chromatography with EtOAc/hexanes to provide 1-4 as a pale yellow solid. Data for 1-4: 1HNMR (500 MHz, CDCl3) δ 7.7 (m, 1H), 7.35-7.25 (m, 5H), 7.05 (m, 2H), 6.8 (m, 1H), 5.45 (m, 1H), 5.35 (m, 1H), 3.9 (m, 1H), 3.4 (m, 1H), 2.4 (s, 3H) ppm. HRMS (ES) calc'd M+H for C19H16F2N2O: 327.1304. Found: 327.1294.

Provenance & Evidence