O‐(2,4‐dinitrophenyl) oximes. Synthesis and cyclization to 5,7‐dinitrobenzofurans

Abstract

We have recently reported (1) the application of the Fischer indole synthesis to the preparation of benzofurans. We wish to describe here the Fischer cyclization of 0-(2,4dinitrophenyl) oximes (In) to 5,7dinitrobenzofurans (IV).Some compounds of the type (111) were reported in the literature (Z), prepared by condensation of oximes with 2,4dinitrochlorobenzene. We synthesized these compounds directly from the carbonyl compounds, condensing them with 0-(2,4-dinitrophenyl)hydmxylarnine (11).A previous attempt to synthesize compound I1 by Ilvespaa and Mancer (3) was reported to fail because of the sensitivity of the aminooxy group. We prepared I1 by condensing t-butyl N-hydroxycarbamate (4) with 2,4dinitrochlorobenzene and treating the resulting t-butyl N-(2,4dinitrophenoxy) carbamate (I) with trifluoroacetic acid. 0-(2,4-Dinitrophenyl) hydmxylamine (11) condensed readily with aldehydes and ketones to give O(2,Cdinitrophenyl) oximes (In). Over sixty compounds of this type 413were prepared but only those used for cyclization are described here. 2,4-Dinitrophenylhydrazones undergo the Fischer reaction only under severe conditions, using sulfuric acid in boiling acetic acid as catalyst (5). We used the same catalyst for the cyclization of compounds (UI) and obtained 5,7dinitrobenzofurans in 3045% yield. The 0-(2,4dinitrophenyl) oximes of acetone, acetophenone and cyclohexanone were cyclized to 5 ,7dinitro-2-methylbenzofuran, 5,7 -&nitro -2-phenylbenzofuran and 6,8 &nitro -1,2,3,4tetrahydrodibenzofuran respectively. EXPERIMENTAL t-Butyl N-(2,4-Dinitrophenoxy)carbmate (I). 2,4-Dinitrochlorobenzene (20.2 g., 0.1 mole) in ethanol (200 ml.) was added dropwise to astirred solution of t-butyl N-hydroxycarbarnate (4) (13.3 g., 0.1 mole) and potassium hydroxide (5.6 g., 0.1 mole) in ethanol (200 d.). The solution which turned deep I II -02NQ---JR R ' N O 2 I V

Sigmatropic rearrangements of 2,4-dinitrophenyl oximes

“…For example, it gave a single HPLC peak, homogeneous by UV, when it was mixed with authentic (13), prepared as described earlier by the oxidation of (11). Its 1 H and 13 C NMR spectra were also identical with those of authentic (13), and with those reported by Kawahara et al for the same compound. 9 These observations confirm that the product obtained was (13) and not its regioisomer 10 (16), which might have been formed in this reaction.…”

“…Melting points are uncorrected and were measured on an Electrothermal 9100 heating ramp. NMR spectra were recorded on a Bruker DPX 400 instrument, operating at 400.14 MHz for 1 H analysis and 100.14 MHz for 13 C analysis. Samples were referenced against tetramethylsilane (TMS).…”

Cytotoxicity of 1-Amino-4-phenyl-1,2,3,6-tetrahydropyridine and 1-Amino-4-phenylpyridinium Ion, 1-Amino Analogues of MPTP and MPP+, to Clonal Pheochromocytoma PC12 Cells

“…We were unsuccessful in attempts to synthesize 1-(methylamino)-4-phenyl-1,2,3,6-tetrahydropyridine, the reduced form of MAPP + , by the reduction of MAPP + with NaBH 4 . Iodide salt of AIQ + (15) was prepared by amination of isoquinoline with O-(2,4dinitrophenyl)hydroxylamine (14). ATIQ hydrochloride (16), iodide salt of MIQ + (11), and MTIQ hydrochloride (11) were prepared with reported procedures.…”

“…2-Aminoisoquinolinium Iodide (Iodide Salt of AIQ + ). Isoquinoline (387 mg, 3 mmol) was dissolved in 5 mL of DMF, and O- (2,4-dinitrophenyl)hydroxylamine (14) (900 mg, 4.5 mmol) was added. The mixture was heated at 60 °C for 15 h. After DMF was removed by evaporation, 5 mL of 1 N HCl was added, and the mixture was washed three times with 5 mL of AcOEt.…”

β-Oxidation of α,β-Unsaturated Carbonyl Compounds

“…]-sigmatropic rearrangements of oxime ethers were studied by many groups, too numerous to list completely, but among them are those of Mooradian,[122][123][124] Sheradsky,125 and Kaminsky 126. No similarly anomalous isohypsic rearrangements were reported.House studied the related rearrangement of N-vinyl hydroxylamine esters to transfer oxygenation on nitrogen to a b-carbon 127.…”