<b>Factors Affecting the Position of Alkylation of Alkali Metal Salts of Pyrrole with Allylic Type Halides</b>

Hobbs, Charles F.; Mcmillin, C.; Papadopoulos, E. P.; VanderWerf, Calvin A.

doi:10.1021/ja00860a011

Cited by 77 publications

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“…The work of Hobbs et al (4) has established that the order of increasing N/C ratio for allyl, crotyl, and benzyl halides is Li+ <Na+ < K+ <NR,+, with the hardest ion, Li', giving most C-substitution, as expected. The even harder Mg2+ of Grignard reagents leads to almost exclusive C-substitution by allyl bromide (5).…”

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confidence: 60%

“…For example, the change from ethers to arenes and alkanes in the reaction of pyrrolylpotassium with allyl halides caused a decrease from 4: 1 to 1 : 6 in the N/C ratio (4). The stepwise addition of the strongly coordinating dipolar aprotic solvent, hexamethylphosphoric triamide (HMPA), to the tetrahydrofuran solution of indolylmagnesium halide caused a regular increase in the N/C ratio of methylation products (8).…”

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confidence: 99%

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Pyrrole chemistry. XVII. Alkylation of the pyrrolyl ambident anion

Wang¹,

Teo²,

Anderson³

1977

Can. J. Chem.

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confidence: 60%

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confidence: 99%

Pyrrole chemistry. XVII. Alkylation of the pyrrolyl ambident anion

Wang¹,

Teo²,

Anderson³

1977

Can. J. Chem.

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“…A few alkylations of the pyrrolyl anion are known where the temperature has been varied from the normal 0-35°C range (8,15,16). We found that while pyrrolyllithium was N-acylated by ethyl carbonate in dioxane at room tempera- For personal use only.…”

Section: Temperaturementioning

confidence: 90%

“…Alkylation studies of pyrrole and indole metal salts and Grignard reagents (8)(9)(10) suggested that a decreasing coordinating ability of the metal (or other) cation leads to increasing dissociation of the ion pair and to an increasing N/C ratio. Shevelev has equated the trend with the decreasing hardness of Mg2+ > LiC > Na' > K C > R,NC, leading to lowered association with the hard centre (N) and decreased hindrance to attack at that position.…”

Section: The Metal Cationmentioning

confidence: 99%

Pyrrole chemistry. XVI. Acylation of the pyrrolyl ambident anion

Wang¹,

Anderson²

1977

Can. J. Chem.

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. Can. J. Chem. 55, 4103 (1977). An investigation of the acylation of the pyrrolyl ambident anion has been carried out. The results have been rationalized in terms of the 'principle of hard and soft acids and bases.' The metal cation, solvent or complexing agent, halide of the pyrrole Grignard reagent, and temperature were varied. As well, the reactions of acylating agents of the carbonyl, cyanide, and carbimine type with the pyrrole Grignard reagent were studied to determine N/C acylation ratios under the same conditions. Several new products were isolated and identified.

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“…The reaction site is dependent on the properties of the metal-nitrogen bond, and on the solvating power of the solvent used. In general, N-substitution is favored by increasing ionic character of the metal-nitrogen bond, and by stronger solvating power (polarity) of the solvent [375,376]. Treatment of pyrrole (1) with potassium metal gives the salt 255 [377], which can thereafter be converted into a wide variety of N-substituted derivatives, for instance the useful 1-(arylsulfonyl)pyrroles 256 (Scheme 4.71) [378].…”

Section: N-metallated Pyrrolesmentioning

confidence: 99%