Metalated 1-(p-methoxybenzyl)pyrazole: a structural chameleon
When treated with either butyllithium or lithium diisopropylamide, 1-(p-methoxybenzyl)pyrazole undergoes metalation at the exocyclic alpha-position but mutates to the 5-lithio species in the course of a few minutes or hours. Trapping the intermediates with a rapidly reacting electrophile such as chlorotrimethysilane or carbon dioxide offers selective access to either of the two possible regioisomers. On the other hand, the relatively inert 1-iodobutane and Bu triflate inevitably give rise to product mixts., as the 5-lithio species is more slowly intercepted than it can revert to the alpha-metalomer by a rapid, though intermol., dynamic equilibration process. [on SciFinder (R)]
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Heterocyclic Compounds (More Than One Hetero Atom)
Institute of Chemical Sciences and Engineering,Ecole Polytechnique Federale,Lausanne,Switz.
written in English.
75-77-4 (Chlorotrimethylsilane); 124-38-9 (Carbon dioxide); 542-69-8 (1-Iodobutane); 75618-25-6 (Butyl triflate); 145162-51-2 (1-(4-Methoxybenzyl)pyrazole) Role: RCT (Reactant), RACT (Reactant or reagent) (metal ion migration in lithiated 1-(p-methoxybenzyl)pyrazole); 288083-61-4P; 902143-97-9P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (metal ion migration in lithiated 1-(p-methoxybenzyl)pyrazole); 162468-73-7P; 162468-78-2P; 162468-82-8P; 902143-98-0P; 902143-99-1P; 902144-00-7P; 902144-01-8P; 902144-02-9P Role: SPN (Synthetic preparation), PREP (Preparation) (metal ion migration in lithiated 1-(p-methoxybenzyl)pyrazole)
Record created on 2007-03-07, modified on 2016-08-08