242 THE PREPARATION OF UNSYMMETRICAL BIARYLS isomers formed. 38- Moreover, itls difficult or impossible to prepare many compounds by direct substitution. Certain compounds which are not available through direct substitution in biphenyl itself have been pre-pared by deamination of substituted ammobiphenyls and benzidines. 28 Grignard Reaction. By addition of an arylmagnesium halide to a eyclic ketone, a carbinol is formed which can be dehydrated and dehydro-genated to a biaryl compound. 39-40-41-42-43-43a For example, m-tolyl-magnesium bromide and cyclohexanol yield 1-m-tolylcyclohexanol, which on dehydration and dehydrogenation gives 3-methylbiphenyl. When applicable, this method is excellent. However, only those biaryls can be prepared which contain.substituents that do not enter into reac-tion readily with Grignard reagents and that can withstand the condi-tions of dehydrogenation. Diels-Alder Reaction.
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This note was uploaded on 11/20/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.