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How the by‐products hint at mechanisms and suggest new synthetic routes in some organolithium reactions
Author(s) -
Nudelman Norma Sbarbati,
García Graciela V.,
Velurtas Susana
Publication year - 2002
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.575
Subject(s) - chemistry , radical , reagent , benzil , alkene , electron paramagnetic resonance , lithium (medication) , reaction mechanism , reaction intermediate , combinatorial chemistry , organic chemistry , computational chemistry , catalysis , medicine , physics , endocrinology , nuclear magnetic resonance
The recent proliferation of structural studies of organolithium reagents has led to an extended knowledge of the aggregation state of these pervasive synthetic intermediates. Nevertheless, detailed investigations of organolithium reaction mechanisms are still very limited. The most popular techniques in the relatively few reported studies are UV, EPR and NMR spectroscopy, the use of radical clocks and investigation of the stereochemical course of the reaction when applied. This paper describes how the search for minor products can be an additional mechanistic tool. Metal–halogen exchange was studied with a new suitable fast radical clock bearing a phenyl group at the alkene C‐terminus, even when the probe was able to trap very short‐lived radical intermediates, the results showed that the reaction proceeds through an open lithiated intermediate. In another study, radicals of benzil were generated on the lithium surface and their reactions studied in THF. Characterization of the minor products, the rates of decay of the reagent and formation of products, and also periodical EPR of the reaction mixture, allowed the proposal of the whole reaction mechanism. In both reactions studied, the detailed understanding of the reaction mechanisms based on the side‐products provided new more economical and environmentally friendly alternatives for the synthesis of substituted 2,3‐dihydrobenzo[ b ]furans and aromatic esters. Copyright © 2002 John Wiley & Sons, Ltd.