Abetract -The reactivltv of Bi" reawntr towards very Wndered phenola with tert.-butvl R~UD~ at 2 and 6 under basic condHiana has been studied. Une&&d phenylatlon at the I-position and, in several cares. repIacement of a fert.-butyl mp by phenyl lihve heen obsewed. The mechanism of thene unexpected reaotions haa Wn diocuesed. Numerous etudfts have been devoted to the oxidative couplinff of phen&. "s' A.wih range al oxldantr har been wed, and amonp them, metal& orlder and saltr play a proeminent. role, 3 In the case of ate&ally hindered phenols, particuIarly the 2,8-d-tcrt. -butyIphenoI , derlvatives, the ooupling' atep involves an aryloxyl radicnL4 Sodium bismuthate behaves no a one-eiectmh oxidant toward8 phenole to give various types of oouplin# pmducte,' In the cam of omobismuth reagent., the flret example of phenol& nxidative coup&g use obrerved in the reaction of 4,6-dlmethylphenol 1 with triphenylbismuth carbonate 1. Wlnth other bismuth reagenta, phenglation occurred. ' Ortho C-phenylation to the cyclohexadienone 2 is reaMred wltb pentaphenylbismuth 2 or with tetraphenplbismuth eaters i or 2 under MC condltlone.? The 0-pbenyl ether is obtained with i under neutral conditions6 or with trlphenylbiemuth diacylates B under copper catalyeis.' During our tnveatigatlons on the regloselectivity of the phenylation of phenols by pentavalent orpano-bismuth realtents, we discovered that ?,6-di-tert.-butylphenol S ie oxidized to the diphenoquinone E by Ph2BiC02 In the prerence of N-teert, -but+N', N', N', N'-tetramethylguenidtne (RTMO). No reaction occurred In abeence of RTMG. Similarly, reaction of 8 with Ph2BiCl2 2 end BTMG led also to the dlphenoauinone 12. -Reaction of %,4,6-triaubetltuted phenols afforded varloue products. Medtol S yielded the 0-or C-phenylatfon product8 under the same conditions ae for itn conmner 1. However, treatment of S with Ph2BiC1, and BTF!G yielded the ortho C-phenyl pmduct fi ln benzene in poor yield, end the (a-methoxylated derivative 5 fn good yield in methanol. %.6-M-tert. -butyI-4-methylphenol 10 Pave aleo the la-mothoxylated derlvatlve g and the cyclohexadlenone 17 in the presence of acrylonitdlel". Various pathways are involved In these reactions. C-phenyletion and come 0-phenylation reactions were explained by the formation of