Deuterium, halogen exchange with

In support of this hypothesis it has been observed that when aluminum bromide is treated with oxygen a reaction occurs which liberates bromine,48 and further, the halogen atoms rather than the hydroxyl group are responsible for the catalytic activity of HOAlBr2. Thus when the compound DOAlBr2 is prepared, the hydrogen-deuterium exchange with n-butane is not at all proportional to isomerization.4 ... 

Azaindolizine, 5-chloro-nucleophilic substitution, 4, 458 8-Azaindolizine, 7-chloro-nucleophilic substitution, 4, 458 Azaindolizines basicity, 4, 454 electronic spectra, 4, 445 electrophilic substitution, 4, 453 halogenation, 4, 457 hydrogen/deuterium exchange, 4, 458 NMR, 4, 447, 449 nucleophilic attack, 4, 458 protonation, 4, 453 reaction with isothiocyanates, 4, 513 reactions, 5, 267 reviews, 4, 444 UV spectra, 4, 446, 449 Azaindolizines, amino-tautomerism, 4, 452... 

Furthermore, if an aldehyde or ketone is treated with D O. the acidic a hydrogens are replaced by deuterium. For a given ketone, the rate of deuterium exchange is identical to the rate of halogenation, implying that a common intermediate is involved in both processes. 

The above considerations do not necessarily apply to reactions of electrophilic reagents with pyrazole and imidazole anions (134, 135). The imidazole anion is sometimes (diazo coupling, halogenation, deuterium exchange) substituted in the 2-position (139) and the indazole anion in the 3-position (cf. Section 3.4.1.4.5). 

A less well developed, but potentially less intrusive alternative is to block acidic sites with deuterium and to use the kinetic isotope effect to prevent lithiation.35 43 If the substrate can be polylithiated, the use of dianions (with the last formed anion being likely to be the most reactive) may give the required selectivity this method works well in the halogen-metal exchange area (section 3.1). 

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