2-Bromo-5-methylpyrrole

As mentioned previously, the final cyclization step requires loss of one of the terminal methyl groups on the a,c-biladiene intermediate. Though no firm mechanistic details have been published on this procedure, which resembles the synthesis of symmetrically substituted dipyrrylmethanes from self-condensation of 2-bromo- or 2-acetoxy-methylpyrroles, it has been noted that cyclization of an a,c-biladiene (204) with vacant positions above the 1-and 19-methyl groups results in production of a formylporphyrin (205), the new formyl... 

The time scale of the build-up and decay of the NOE is often such that it can be used to study processes that proceed appreciably more slowly than those aceessible to band-shape studies. This has been used in studies of restricted rotation in amides (205,214) the cis-trans equilibrium of 4-bromo-2-formyl-l-methylpyrrole (215) exchange in water solution of the system l-(T-pyrazolyl)ethanol-acetaldehyde (216) and the cis-trans equilibrium in 4-bromo-2-formylfuran. (217)... 

Depending on the reaction conditions, 1-methylpyrrole (17) can be brominated at C-2 with NBS to give 2-bromo-1-methylpyrrole (18) or at C-3 with NBS and catalytic PBr, to give 3-bromo-l-methylpyrrole (19). Both reactions are essentially quantitative, but both 18 and 19 decompose on silica gel [26],... 

NBS is used as a reagent for phenylselenyl activation in a route to aziridines and oxazolidin-2-ones. The synthesis of 5-bromoisoquinoline and 5-bromo-8-nitroisoquinoline has been achieved using NBS. 3-Bromo-A-methylpyrrole can be obtained from A-methylpyrrole by the use of NBS and a catalytic amount of PBrs. A new synthetic route to indoloquinones has appeared in which 2-methoxy-2//-azepine derivatives react with NBS to form 3//-azepines. Convenient methods for the bromination of 3,5-diarylisoxazoles and for the synthesis of... 

Under conditions of acid catalysis 1-methylpyrrole was largely chlorinated by A -chlorobenzamide (Scheme 14). There was evidence of an amplified isotope effect kmko = 19.10 at 40°C), which points to deprotonation of the sigma-complex being rate-determining. Thus, the chlorination process should be reversible (89CC1466). The observed instability of 2-chloropyrrole in acidic medium supports this (75JOC3161). (See also 3,b and 3,c for reactions of W-bromo- and N-iodo-imides.)... 

In the pyrrole series h ogenated azides can be prepared by direct halogenation. 2,4r-Dimethyl-3-ethylpyiTole-5-carbonyl azide has been brominated to 2-bromomethyl-3-ethyl-4-methylpyrrol n5-car-bonyl azide and 2-methyl-3,4-diethylpyrrole-5-carbonyl azide (XXIX) has been chlorinated with sulfuryl chloride to 2-trichloro-methyl-3,4-diethylpyrrole-5-carbonyl azide, which on treatment with methanol yields 3,4-diethyl-2-carbomethoxy-5-carbomethoxyaminopyr-role (XXX). Dichlorination is also successful 2,4-dimethyl-3-bromo-... 

Clearly, protonation at either a-position is possible accordingly, it is not surprising that 5-bromo-4-ethyl-3-methylpyrrole-2-carboxylic acid gives a mixture of hydroxy compounds. ... 

Cycloaddition of oxyallyl cations to N-methylpyrrole and furan leads to novel analogues of cocaine (Scheme 74). ° In a somewhat related synthesis the tropane skeleton has been prepared using bromo-ketone-iron carbonyl coupling to pyrroles (Scheme 75). ° ... 

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