Of 2-methyl-5-phenylpyrrole

The nitration of 2-methyl-5-phenylpyrrole yields predominantly the 3-nitro derivative (5a). Other electrophiles also react at the 3-position to form products (5b,c,d)[73AC(R)245]. 

The nitrosation of 2-methyl-5-phenylpyrrole yields the 3-nitroso derivative predominantly (60%) together with the 4-nitroso product (30%) [71 AC(R)237]. 

The nitrosation of 2-methyl-5-phenylpyrrole has been reported to give the 4-nitroso derivative (60JCS3270), but later work has shown that the reaction gives a mixture of two isomers in a 2 1 ratio [71 AC(R)546], An unusual reaction was also reported for 2,5-diphenylpyrrole with sodium nitrite in aqueous acetone at 0°C when treated with 2 M hydrochloric acid. The principal product is 3-diazonio-4-nitro-2,5-diphenylpyrrole (12)... 

Triphenylvinylphosphonium salts are usually used as dipolarophiles against azides and diazoalkanes30. 2,3-Diphenyl-2//-azirine and 1-azido-l-phenylpropene as precursors of 2-methyl-3-phenyl-2H-azirine produce, after irradiation, 2,5-diphenylpyrrole and 2-methyl-5-phenylpyrrole, respectively29. 

The action of potassium nitrate in concentrated sulfuric acid at 0°C (0.5 h) converts 3-acetyl-2-methyl-5-(2-nitrophenyl)pyrrole (11) to the 4-nitro product (40%). 2-Methyl-5-(2-nitrophenyl) and 2-methyl-5-(2-ni-trophenyl)-l-phenylpyrrole yield the 3-nitro products under similar conditions. 

The heteronuclear variant of NOESY is HOESY (Heteronuclear Overhauser Effect SpectroscopY). Figure 4.60 shows a HOESY spectmm for the tetramethylethylenediamine (tmeda) adduct of 2-lithio-l-phenylpyrrole, whose dimeric structure is also shown in the figure. The normal H and Li NMR spectra are shown along the axes of the 2D contour plot, which contains just three peaks. The lithium atom is therefore close (i.e. less than about 3.5 A) to three different sets of three protons, which can be readily identified as H(7) and H(ll), equivalent by virtue of fast rotation about the N(l)-C(6) bond in solution, H(3), and the methyl protons of the tmeda ligand. Note that the hydrogen atoms are numbered according to the numbers of the carbon atoms to which they are attached. The close contact between Li and H(11) seen in the crystal structure is thus maintained in solution, and it is of chemical significance, as it leads to... 

Namely, the reaction of 2-thioxothiazolidin-4-one N-hexanoic acid (116) with 2,5-dimethyl-l-phenylpyrrol-3-carboxaldehyde (117) in methanol under the catalytic action of ethylenediamine diacetate (EDDA) yields 5-[(2,5-dimethyl-l-phenylpyrrol-3-yl)methylidene]-2-thioxothiazolidin-4-one N-hexanoic acid (118) in 79% yield. The hydroxamate derivative of 118 is prepared by reacting this compound with 0-(tetrahydro-2H-pyran-2-yl)hydroxylamine followed by treatment with p-toluenesulfonic acid in methanol to afford compound 121 in 60% yield. Esterification of compound 118 is carried out by using methyl iodide in acetonitrile in the presence of sodium carbonate to give compound 120. The 5-(cyclohexyl)methylidene analogue (119) is obtained in 42% yield by direct reaction of compound 116 with cyclohexanecar-boxaldehyde in methanol under the catalytic action of EDDA. 

Sheradsky has found that the hydroxyl function of a ketoxime such as acetophenone oxime can be made to react with DMAD when the reaction is carried out in methanol with a basic catalyst, to give mixture of the fumarate and maleate isomers (164) in the ratio 2 1. This mixture on heating undergoes a hetero-Cope rearrangement followed by cyclization and dehydration to give dimethyl 5-phenylpyrrole-2,3-dicarboxylate (168) (Scheme 25). Similarly, Heindel and Chun have reported that vinyl ether adducts (171), obtained by the condensation of arylamide oximes with DMAD, get thermally converted into oxa-diazolines (172) or imidazolinones (174), depending on the reaction conditions. A similar reaction occurs with aromatic amidoxime-methyl propiolate adducts to give imidazoles (170) (Scheme 26). 1,2,4-Dioxazoles have been reported to be formed in the reaction of hydrox-amic acids with DMAD. - ... 

Fig. 3. Solvent effect on the yield of 2-phenylpyrrole [89KGS29I] I, DMSO 2, HMPA 3, l-methyl-2-pyrrolidone 4, sulfolane 5, PEG 6. tetramethyl urea. Catalyst KOH (0.5 mol/L), for other reaction conditions see Fig. 1.

The cephalic extracts of the ants Anochetus kempfi and A. mayri were found to contain 2,5-dimethyl-3-isoamylpyrazine (121) and 3-methyl-4-phenylpyr-role (122) (Fig. 20). This is the first report of a phenylpyrrole in an insect [128]. These compounds are most likely mandibular gland products and have a pheromonal role. 

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