Acetic Acid → 6-Hydroxy-2,2-dimethyl-5-nitro-chroman-4-one

Beteiligte Stoffe

Reaktionsschritte

To a 250 mL round bottom flask equipped with a magnetic stir bar was added 3 (810 mg, 4.2 mmol) and 15 mL of glacial acetic acid. The mixture was stirred at room temperature until all of the solid dissolved. To a 25 mL vial was added KNO3 (469 mg, 4.6 mmol) and just enough distilled water to dissolve all the KNO3. The aqueous KNO3 solution was transferred to the reaction flask with a pipet. The reaction flask was lowered into an ice water bath (˜10° C.). Concentrated H2SO4 (1 mL) was added drop-wise. The mixture was stirred until all starting material was consumed, as monitored by TLC analysis. Ethyl acetate (20 mL) was added, and the biphasic mixture was transferred into a 500 mL separatory funnel. Saturated aqueous Na2CO3 was added cautiously until the aqueous layer was pH˜7. The aqueous phase was extracted in ethyl acetate (3×20 mL), the combined organic phases were washed with brine (1×50 mL), dried over MgSO4, filtered, concentrated and dried under high vacuum. The dry crude product was passed through a silica gel column using 25:1 CH2Cl/EtOAc as eluent (Rf=0.3). The product gives off a red color on an analytical silica gel plate illuminated with a shortwave UV lamp. The fractions containing the pure product were transferred to a pre-weighed flask, the solvent was evaporated and the concentrate was dried under high vacuum. The reaction furnished 715 mg (72%) of 4 as a yellow solid. 1H NMR (300 MHZ, CDCl3): δ 7.70 (bs, 1H), 7.21 (d, J=9 Hz, 1H), 7.04 (d, J=9 Hz, 1H), 2.76 (s, 2H), 1.46 (s, 6H). 13C NMR (75.5 MHZ, CDCl3): δ 188.9, 154.4, 145.0, 126.4, 124.7(2), 113.1, 80.6, 49.0, 26.4; HRMS (EI+): calculated for C11H11NO5[M+] m/z 237.0637, found 237.0633.

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