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Regioselectivity of pyrazole bromination
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Mike Eisler
Regioselectivity of pyrazole bromination
The explanation I would produce as someone with no specific knowledge of heterocycles, or this specific reaction, is that substitution on the left side proceeds through an electron-deficient carbon intermediate, while substitution on the right side proceeds through an electron-deficient nitrogen intermediate. The latter is a higher energy intermediate.
The explanation I would produce as someone with no specific knowledge of heterocycles, or this specific reaction, is that substitution on the left side proceeds through an electron-deficient carbon intermediate, while substitution on the right side proceeds through an electron-deficient nitrogen intermediate. The latter is a higher energy intermediate.More
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Without me reading the whole paper, the selectivity is due to a wheland (arenium) intermediate forced by a quarternary ion (off the "pyridine nitrogen).
Without me reading the whole paper, the selectivity is due to a wheland (arenium) intermediate forced by a quarternary ion (off the "pyridine nitrogen).More
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Hi all - recently began studying heterocyclic chemistry, and came across the following problem. From my understanding, the methylated nitrogen is pyrrole-like, and the other nitrogen is pyridine-like. The rationalization I've heard for this selectivity is that the pyridine-like nitrogen directs substitution towards the 2-position. However, wouldn't pyrrole-like reactivity suggest that bromination takes place at the 1 position, adjacent to the pyrrole-like nitrogen? Given these two, why does the pyridine-like nitrogen dictate the reactivity more?
Hi all - recently began studying heterocyclic chemistry, and came across the following problem. From my understanding, the methylated nitrogen is pyrrole-like, and the other nitrogen is pyridine-like. The rationalization I've heard for this selectivity is that the pyridine-like nitrogen directs substitution towards the 2-position. However, wouldn't pyrrole-like reactivity suggest that bromination takes place at the 1 position, adjacent to the pyrrole-like nitrogen? Given these two, why does the pyridine-like nitrogen dictate the reactivity more?More
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