Phenol quinones from

In small-scale syntheses, a wide variety of oxidants have been employed in the preparation of quinones from phenols. Of these reagents, chromic acid, ferric ion, and silver oxide show outstanding usefulness in the oxidation of hydroquinones. Thallium (ITT) triduoroacetate converts 4-halo- or 4-/ f2 -butylphenols to l,4-ben2oquinones in high yield (110). For example, 2-bromo-3-methyl-5-/-butyl-l,4-ben2oquinone [25441-20-3] (107) has been made by this route. 

Use of transition metal catalysts opens up previously unavailable mechanistic pathways. With hydrogen peroxide and catalytic amounts of methyl trioxorhe-nium (MTO), 2-methylnaphthalene can be converted to 2-methylnaphtha-l,4-qui-none (vitamin K3 or menadione) in 58 % yield and 86 % selectivity at 81 % conversion (Eq. 10) [43, 44]. Metalloporphyrin-catalyzed oxidation of 2-methylnaphtha-lene with KHSOs can also be used to prepare vitamin K3 [45]. The MTO-catalyzed process can also be applied to the synthesis of quinones from phenols [46, 47]. In particular, several benzoquinones of cardanol derivatives were prepared in this manner [48], The oxidation is thought to proceed through the formation of arene oxide intermediates [47]. 

Quinones from phenols Under acidic conditions (70% perchloric acid in HOAc) phenols are converted to p-benzoquinones at room temperature. The oxidation proceeds even with p-halophenols such as 2,4,6-trihalophenols, giving 2,6-dihalo-p-benzoquinones in high yields. 

Phosphomolybdic acidjhydrogen peroxide /7-Quinones from phenols... 

Perchloric acidithallic oxide Quinones from phenols with C-alkyl migration... 

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