Alkyl groups pyrrole

The nitrosation of pyrroles and indoles is not a simple process. The 3-nitroso derivatives (84) obtained from indoles exist largely in oximino forms (85) (80IJC(B)767). Nitrosation of pyrrole or alkylpyrroles may result in ring opening or oxidation of the ring and removal of the alkyl groups. This is illustrated by the formation of the maleimide (86) from 2,3,4 -trime thylpyrrole. 

The second structural type found for organometallic cobalt porphyrins contains an organic fragment bridged between the cobalt and one pyrrolic nitrogen. Cobalt complexes of N-alkyl- or N-arylporphyrins arc well established (but will not be specifically addressed here). The bridged complexes are derivatives of these where the N-alkyl group also forms a cr-bond to cobalt. They are also related to the axially... 

Redistilled N, O-persilylated L-proline 438 reacts with pivaldehyde in pentane at ambient temperature to give the 0,N-acetal 439 in 78% yield in the presence of LDA this condenses, a to the carbonyl group, with N-alkyl-2-pyrrole aldehydes [48] (Scheme 5.14). 

Fig. 1 Schematic drawing showing the structure of tris(A/,AT-disubstituted-dithiocarbam-ato)iron(III). Substituents R1 and R2 represent various types of alkyl groups including those being part of the ring systems morpholine, pyrrolidine or pyrrole (Table 1)... 

These authors also demonstrated that the outcome of analogous additions of lithiated alkoxyallenes 120 to isothiocyanates is highly dependent on the nature of the alkyl group in the isothiocyanates as depicted in Schemes 8.34and 8.35 [88, 91]. Whereas methyl isothiocyanate 134 leads to pyrrole derivative 135, the correspond-... 

The initial report within this area described the regiospecific alkylation of pyrroles using imidazolidinone 12 (20 mol%) as the catalyst [82]. A mixture of THF and water provided optimal reaction conditions, but low temperatures (-60 °C to -30 °C) were required to ensure the chemospecificity of the reaction. The functional group tolerance at the P-position of the substrate and A-substitution on the pyrrole nucleophile was explored (Scheme 15). It was noticed that subtle changes in the nature of the co-acid altered selectivities and this had to be modified depending on the substrates adopted. 

Nitrosation of pyrrole or alkylpyrroles may result in ring opening or oxidation of the ring and removal of the alkyl groups. This is illustrated by the formation of the maleimide (119) from 2,3,4-trimethylpyrrole. 

The introduction of alkyl groups on pyrroles, indoles, isoindoles and carbazoles can usefully be subdivided according to the desired locus of substitution. There are three distinct... 

---