Pyrroles substitution

A one-pot procedure from aldehydes, through Wittig olefmation and a subsequent epoxidation, was also reported. Aldehydes could be converted into a,P,y,8-unsaturated N-acyl pyrroles, which were epoxidized in the same pot to give N-acyl pyrrole-substituted vinylepoxides [32]. 

Benzyl isocyanoacetate is a useful reagent for the preparation of benzyl 5-unsubstituted pyrrole-2-carboxylates, which are widely used in the synthesis of porphyrins.23 Ono and coworkers have prepared pyrroles substituted with various substituents at the (3-positions.231 Because the requisite (3-nitro acetates (or nitroalkenes) are readily available by the Henry... 

Barton-Zard pyrrole synthesis is also applied to synthesis of pyrroles with a variety of substituents. Pyrroles substituted with long alkyl substituents at the 3 and 4 positions,30 pyrroles with P-CF3 (Eq. 10.26),31 3,4-diarypyrroles (Eq. 10.27),32 and pyrrole-2-phophonates (Eq. 10.28)33 are prepared in a similar manner based on isonitrile cyclization. 

Nitroalkenes derived from galactose or other carbohydrates are converted directly into pyrroles substituted with such carbohydrates at the (3-position. They are important precursors for water-soluble porphyrins (Eq. 10.29).34 Such kinds of porphyrins are good candidates for photodynamic therapy of cancer and have been extensively studied. 

Polymeric films of [(//5-C s Me5)M(L)Cl]+complexes (M = Ir, Rh L = pyrrole-substituted bpy or phen) have been coated on an electrode by oxidative electropolymerization. The buildup of hydrido complexes in films is well known 27,28,30 the high electrocatalytic activity of these molecular electrode materials towards dihydrogen evolution in organic and aqueous electrolytes is also well known.25,31 For example, H2 is evolved at —0.55 V vs. SCE at a poly [(j75-C5Me5)-Rh(bpy)Cl]+ film in pH 1 aqueous solution.31... 

Complex (21), a Con-cyclam analogue, is very active for the reduction of N02 and NH2OH intermediates and catalyzes the complex electrochemical conversion of N03 to NH3 325 Gold electrodes modified with cobalt-cyclam incorporated in Nafion films,324 or by electropolymerization of the pyrrole-substituted cobalt cyclam (22)326 have shown catalytic activity for the reduction of nitrate in strongly basic media. 

A Nazarov-type cyclization was exploited to prepare annelated pyrroles <06OL163>. Acylation of iV-tosylpyrrole 65 with carboxylic acid 66 promoted by trifluoroacetic anhydride gave intermediate 2-ketopyrrole 67 which underwent a Nazarov-type cyclization to give cyclopenta[fc> pyrrolc 68. Another route to cyclopenta[fc]pyrroles involved a novel cyclization involving pyrrole-substituted enones and isocyanides <06OL3975>. 

The reaction of 2equiv. of a pyrrole-substituted cyclopentadiene with Zn[N(SiMe3)2]2 (Scheme 19) afforded the dicyclopentadienylzinc complex 23.52 A solid-state structure of this compound was not obtained, but room-temperature 1H NMR spectroscopic studies showed two equivalent cyclopentadienyl groups, whose signals broadened on cooling. 

Dipolar cycloaddition of nitrile oxide 425 with allyl bromide followed by hydrogenation of dihydroisoxazole derivative 426 (Scheme 1.54) gives a pyrrol-substituted steroid derivative 427 (466). 

As will be seen in this chapter and in the rest of the book, the Heck reaction and its numerous variations represent a fantastically powerful set of tools available to the heterocyclic chemist. Although most Heck chemistry that involves pyrroles is intramolecular or entails synthesis of the pyrrole ring, a few intermolecular Heck reactions of pyrroles are known. Simple pyrroles (pyrrole, A-methylpyrrole, A-(phenylsulfonyl)pyrrole) react with 2-chloro-3,6-dialkylpyrazines under Heck conditions to give mixtures of C-2 and C-3 pyrrole-substituted pyrazines in low... 

Although MO calculations do give an indication of the relative reactivity of the a- and /3-positions, no satisfactory explanation has been proposed for the relatively unreactive character of the nitrogen atom. In all theoretical calculations, the charge density on the nitrogen atom is considerably higher than on the carbon atoms. This anomaly may only be explained when we have more detailed information on the mechanism of pyrrole substitution reactions. 

Ravikanth and coworkers have synthesized (S-pyrrole-substituted 21,23-dithiaporphyrins by refluxing 21,23-dithiaporphyrin with NBS in chloroform. (5-Aryl-substituted thiaporphyrin 238 (Scheme 94) has been obtained by condensing 3,4-disubstituted pyrroles 237 with thiophene diol 222 (X=S) under mild acid conditions (00CL480). 

The indole (78) and pyrrole (79) derivatives, containing phosphabenzene with a dicoordinated phosphorus atom as substituent, were obtained [76] in the reaction of indole- and pyrrole-substituted pyrrylium salts with trimethylolphosphine ... 

Pyrrole-substituted [1-amino ester 394 was synthesized via aza-Michael conjugate addition (Scheme 81) [149]. 

Obirai J, Rodrigues Pereira N, Bedioui F, Nyokong T (2003) Synthesis, spectral and electrochemical properties of a new family of pyrrole substituted cobalt, iron, manganese, nickel and zinc phthalocyanine complexes. J Porphyrins Phthalocyanines 7(7) 508-520... 

Rodrigues Pereira N, Obirai J, Nyokong T, Bedioui F (2005) Electropolymerized pyrrole-substituted manganese phthalocyanine films for the electroassisted biomimetic catalytic reduction of molecular oxygen. Electroanalysis 17(2) 186-190... 

Diazotization of the amino group of the pyrrole-substituted pyridine (286) using NaN02 in aqueous AcOH, together with a concommitant cyclization, gave the pyridotriazine (287) (64%) <85CPB4242>. 

Watanabe M, Koike H, Ishiba T, Okada T, Seo S, Hirai K. Synthesis and biological activity of methanesulfonamide pyrimidine- and N-methanesulfonyl pyrrole-substituted 3,5-dihydroxy-6-hep-tenoates, a novel series of HMG-CoA reductase inhibitors. Bioorg. Med. 

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