Pyrrole chemistry. XXIV. The Vilsmeier formylation and the cyanation of pyrrole acetals. A synthesis of pyrrole-2,3,5-tricarboxaldehyde

Abstract

. Can. J. Chem. 60, 383 (1982). The preparation of the acetals of a number of pyrrole mono-and dicarboxaldehydes is described. It is shown that, provided the reactivity of the unsubstituted ring positions on the pyrrole nucleus is not too low, a carboxyaldehyde or a carbonitrile group may be substituted onto the pyrrole ring using the Vilsmeier reaction or chlorosulfonyl isocyanate respectively. Vilsmeier formylation of the diacetal, 2,4-di(5,5-dimethyl-1,3-dioxan-2-yl)-pyrrole, followed by hydrolysis gave pyrroie-2,3,5-tricarboxaldehyde.CHARLES E. LOADER, GRAHAM H. BARNETT et HUGH J. ANDERSON. Can. J. Chem. 60,383 (1982). On decrit la preparation des acttals d'un certain nombre de pyrroles mono et de dicarboxaldehydes. On montre, en admettant que la reactivite des positions non substituees du noyau pyrrole n'est pas trop faible, que I'on peut substituer un groupe carboxaldehyde ou carbonitrile du cycle pyrrole en utilisant soit la reaction de Vilsmeier ou I'isocyanate de chlorosulfonyle. La formylation de Vilsmeier du diacetal, di (dimethyl-5,5 dioxanne-1,3 yl-2)-2,4 pyrrole, suivie d'une hydrolyse donne le pyrroletricarboxaldehyde-2.3.5.[Traduit par le journal] Introduction prepare the diacetal, 2-(5,5-dimethyl-l,3-dioxan-2-We recently reported the synthesis of 2-(5,5-di-yl) -4-(2,5,5-trimethyl-1,3 -dioxan-2-yl) -pyrrole,

Yellow NIR dye: π-fused bisbenzoBODIPYs with electron-withdrawing groups

“…Conversion of ester groups of 12 to cyano groups by the reported method 22 failed. Therefore, the ester groups of 12 were all removed by treatment with KOH in hot ethylene glycol followed by cyanation of the resulting free bis(dipyrromethane) with chlorosulfonyl isocyanate, 23 which gave the desired tetracyano derivative 13 in 88% yield. Oxidation of 13 in the presence of BF 3 •OEt 2 and triethylamine afforded BCOD-fused bisBODIPY tetra-nitrile 14 in 28% yield.…”

Identification of a New Pyrrolyl Pyridoindole Alkaloid, Melpyrrole, and Flazin from Honey and Their Cough-Suppressing Effect in Guinea Pigs

“…This compound was prepared from commercially available 3 according to the methods of Schmuck and Loader . Thus, phosphorus oxychloride (3.69 mL, 39.6 mmol) was added dropwise to ice cold N , N -dimethylformamide (3.06 mL, 39.6 mmol), and then the mixture was diluted with dichloromethane (20 mL).…”

“…The combined organic layers were washed with brine, dried, and concentrated. The residue was chromatographed on silica gel ( n -hexane–ethyl acetate = 10:1 → 8:1 → 6:1) to give 4 (2.04 g, 98%) as a white solid whose spectral data were consistent with those of the literature …”

“…The combined organic layers were washed successively with water and brine, dried, and concentrated. The residue was chromatographed on silica gel (nhexane−ethyl acetate = 10:1 → 4:1 → 2:1) to give 11 (1.37 g, 92%) as a light-yellow solid; 1 H NMR (500 MHz, CDCl 3 ): δ 9.04 (1H, brs), 8.36 (1H, s), 7.63 (1H, d, J = 7.9 Hz), 7.33 (1H, t, J = 7.9 Hz), 7.12 (1H, t, J = 7.9 Hz), 6.82 (1H, d, J = 7.9 Hz), 6.57 (1H, d, J = 3.4 Hz), 6.35 (1H, d, J = 3.4 Hz), 4.85 (2H, brs), 4.75 (2H, s), 4.23 (3H, s), 4.03 (3H, s), 3.47 (3H, s); 13 [3,4-b]indole-3-carboxylate (12). A 10% HCl solution in methanol (12 mL) was added dropwise to a stirred solution of 11 (1.0 g, 2.25 mmol) in dichloromethane (24 mL) at rt, and the mixture was stirred at the same temperature for 4 days and then concentrated.…”

“…Hz), 3.61 (2H, brd, J = 11.2 Hz), 1.52 (1H, t, J = 5.9 Hz), 1.26 (3H, s), 0.79 (3H, s);13 C NMR (125 MHz, CDCl 3 ): δ 131.1, 129.5, 107.2, 106.5, 96.7, 77.4, 58.3, 30.2, 23.0, 21.9; HRMS (ESI + ) calcd for C 11 H 18 O 3 N [M + H] + 212.1287, found 212.1287.…”