The reaction of the 2,6-di-tert-butyl-4-methylphenoxy radical with phenols
作者:Kanji Omura
DOI:10.1021/jo00003a006
日期:1991.2
Dimer 3 dissociates in solution to give the phenoxy radical 4. When solid 3 is dissolved in a solution of phenol 11a, radical 4 dehydrogenates the phenol to afford phenol 5 and phenoxy radical 12. Radical 12 couples with more 4 to afford principally bis(cyclohexadienone) 16a and a minor amount of the dimeric bis(cyclohexadienone) 13. The preferential formation of 16a over 13 is explained as the result of a solvent-cage reaction. Compounds 13 and 16a are isomerized in the presence of silica gel or triethylamine to 4,4'-dihydroxybiphenyl 14 and phenolic dienone 17a, respectively. Compound 13 is relatively stable in hexane at 30-degrees-C, while 16a slowly dissociates under these conditions to afford parent radicals 4 and 12. If 11a is present, radical 4 either recombines with 12 or dehydrogenates the phenol. Two radicals of 12 generated by the dissociation of 16a and the subsequent dehydrogenation of 11a couple to give 13. Therefore, dissolving 3 in hexane containing excess 11a and keeping the resulting solution at 30-degrees-C results in the preferential formation of 13. Dissolving 3 in triethylamine containing phenols 11 or 21 similarly affords dienones 17 or 23. The yields of these dienones increase with increasing electron-donating capability of the substituent on the phenol ring.
OMURA, KENJI, J. ORG. CHEM., 56,(1991) N, C. 921-926
作者:OMURA, KENJI
DOI:——
日期:——
DROST, KEVIN J.;CAVA, MICHAEL P., J. ORG. CHEM., 56,(1991) N, C. 2240-2244