N-Methylpyrrole

The precedent is strong for the involvement of oxetanes as Intermediates in carbonyl additions to pyrroles. " NMR evidence has been obtained far an oxetane adduct of acetone and N-methylpyrrole. The initial photoadduct was shown to rearrange readily on workup to the 3-(hydroxyalkyl)pyrrole derivative. 

Photochemical [2 + 2] cycloaddition is a powerful way to produce cyclobutanes, which, in turn, are reactive synthesis intermediates. N-Methylpyrrole adds aldehydes via [2 -I- 2] photocycloaddition to give transient oxetanes with high regioselectivity Ring-opening produces 3-(oi-hydroxyalkyl)pyrroles which are oxidized easily to 3-arylpyrroles, such as 3-BUTYROYL-l-METHYL-PYRROLE. With a special apparatus, ethylene is conveniently added to 3-methyl-... 

Fluorination of N-methylpyrrole over cobalt trifluoride gives six polyfluo-rinated Af-methylpyrrolidines The same compounds and two others and perfluoro-1-methylpyrrolidme are obtained by fluorination of N-methylpyrrolidine. The yields of the individual products are low [75] (equation 8)... 

The dimer of 1-methyl- -pyrroline (39) was obtained by reduction of N-methylpyrrole with zinc and hydrochloric acid (132) and, together with the trimer, by mercuric acetate dehydrogenation of N-methylpyrrolidine (131). J -Pyrroline-N-oxides form dimers in a similar manner (302). Treatment of 1,2-dimethyl-zl -piperideine with formaldehyde, producing l-methyl-3-acetylpiperidine (603), serves as an example of a mixed aldol reaction (Scheme 18). 

An interesting rearrangement which is based on the intramolecular acylation of an enamine by an ester is found in the aromatization of the adduct derived from N-methylpyrrole and an acetylenedicarboxylic ester (407,408). 

The use of pyrrole and N-methylpyrrole was found to be preferable. Through the addition of N-methylpyrrole, all cationic side reactions could be effectively suppressed, and only dimerization products produced by Ni-catalysis were obtained. In this case the dimer selectivity was as high as 98 %. Scheme 5.2-21 shows the catalytic system that allowed the first successful application of [(H-COD)Ni(hfacac)] in the biphasic linear dimerization of 1-butene. 

The amino acid 58 was used in the solid-phase synthesis of sequence-specific DNA binding polyamides containing N-methylimidazole and N-methylpyrrole amino acids <96JACS6141> and it was also reported that the imidazole-acridine conjugate 59 could effectively catalyze the cleavage of t-RNA <96TL4417>. 

Nguyen, D.H., J. W. Szewczyk, E.E. Baird, and P. B. Dervan. Alternative heterocycles for DNA recognition An N-methylpyrazole/N-methylpyrrole pair specifies for A-T/T-A base pairs. Bioorg. 

T.A. Beerman, and P.B. Dervan. Cellular uptake of N-methylpyrrole/N-methyli-midazole polyamide-dye conjugates. 

Konno, A., Mogi, I. and Watanabe, K. (2001) Effect of strong magnetic fields on the photocurrent of a poly(N-methylpyrrole) modified electrode. 

For example, Mannich reaction of N-methylpyrrole affords the corresponding dimethylaminomethyl derivative (2) and treatment with methyl iodide affords the quaternary salt (3). Displacement of the quaternary amine by means of cyanide leads to the substituted... 

HDZ = hydrazine Igepal CO-520 = polyoxyethylene(5)nonylphenyl ether ISO = isooctane LAc = linoleic acid MA = methylamine MST = mesitylene Ni°(cod)2 = bis (r]4-l,5-cyclooctadiene) Ni(0) NMPyr = N-methylpyrrole OA = oleylamine OAc = oleic acid Oc = octane OcA = octylamine ODA = octadecylamine PAA = poly (acrylic add) PD = 2-pyrrolidone Igepal CA-520 = polyoxyethylene(5)isooctylphenyl ether PVP = polyvinylpyrrolidone Pyr = pyrrole RAc = ricinoleic acid ... 

Ab initio calculations have also been applied to certain prototype lexitropsins in which one of the N-methylpyrrole moieties of netropsin was replaced by 1-methylimidazole.54 The rationale for this replacement was an attempt to invoke hydrogen bonding between the... 

Table 18. Regioselectivity of ketocarbenoid insertion into C—H bonds of N-methylpyrrole.

Incidentally, oxidation data of the pyrrole monomers show an interesting increase in oxidation potentials when containing heavier substituents (Table 25). However, the ionization potential of N -methylpyrrole (7.95 V) is smaller than that of pyrrole (8.21 V). The accepted linear relationship between ionization potential and oxidation potential210 would have it the other way round. Considering, however, that trimethylsilyl and trimethylgermyl groups are weak electron donors211, it is plausible that a nonelectronic effect is responsible for the observed trend and the potential shifts are associated with steric effects. 

The UV spectrum of 30 (Fig. 16) exhibits a large bathochromic shift (Amax = 270 nm) compared to other related compounds such as 2-pen-tamethyldsilanyl-N-methylpyrrole (Amax = 248 nm). A similar bathochromic shift is observed in charge-transfer complexes of pyrrolo-... 

Scheme 6.63 Addition of atomic carbon to pyrrole and N-methylpyrrole and interception of the zwitterions 179-Zn and 293-Z, by electrophiles, according to Shevlin and co-workers.

Scheme 6.92 Generation of the cephalosporin-derived cyclic allene 450 from the cephalosporin / -S-oxide triflate 449 and trapping of450 by (Z)-/J-deuterostyrene, furan, 2-acetylfuran, furan-3-carboxylic acid dimethylamide, N-tert-butoxycarbonylpyrrole, pyrrole and N-methylpyrrole.

In a similar way, benzofurans and N-methylpyrrole afford 2,3-dimethoxylated derivatives (Scheme 97) [160]and2,5-tetra-methoxy-2,5-dihydro-AI-methylpyrrole, respectively (Scheme 98) [57, 161,162]. 

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