Water → 6,7-Methylenedioxy-3-nitro-4-(2-[1,3]dioxan-2-yl-phenyl)-3,4-dihydro-(2H)-chromene

Participants

Reaction Conditions

Reaction Steps

Acetal (5a) (9.04 g, 37.22 mmol) was dissolved in 50 ml of dry THF under an inert atmosphere in a two necked flask equipped with a condenser. Magnesium (1.8 g, 74.44 mmol) and one drop of 1,2 dibromoethane were added. This mixture was stirred at 80° C. for 45 min, and cooled to room temperature. A 50 ml solution of 2.74 g of nitrochromene (3a) (12.41 mmol) in THF was cannulated into this flask. This mixture was stirred for 30 min, and water was added to quench the reaction. The mixture was extracted with CH2Cl2 (100 ml×3), the extracts washed with brine (100 ml), dried over MgSO4 filtered, and the solvent evaporated to a brown oil from which (6a) precipitated spontaneously. The precipitate was filtered, rinsed with 30 ml of EtOAc and dried to give 2.91 g (61.4% yield). The remaining liquor was purified by flash column chromatography to give an additional 550 mg (72% combined yield): mp 207° C.; 1H-NMR (CDCl3) δ 7.50 (m, 1, ArH); 7.29 (m, 2, ArH); 6.99 (m, 1, ArH); 6.47 (s, 1, ArH); 6.38 (s, 1, ArH); 5.90 (d, 2, ArOCH2); 5.70 (s, 2, OCH2O); 4.97 (s, 1, O2CHAr); 4.71 (dq, 1, Ar2CH, J=10 Hz); 4.23 (m, 2+1, CH2(CH2O)2, CHNO2); 3.98 (m, 2, CH2(CH2O)2); 2.22 (m, 1, CH2); 1.43 (d, 1, CH2); Low resolution CIMS: m/z (rel. intensity) 386 (MH+, 100). Anal. Calcd. for C20H19NO7: C, 62.33; H, 4.97; N, 3.63. Found: C, 62.18; H, 5.37; N, 3.38.

Provenance & Evidence