Allyl phenols, oxidation

Phenolic derivatives were prepared and then converted into thioether analogs using ethanedithol followed by oxidation of this intermediate to the disulfide. Phenolic resins were prepared by electrophilic substitution of allyl phenol derivatives with formaldehyde and then flee radically copolymerizing with ethanedithol. Epoxidation was performed using epichlarohydrine. 

The facile electrocyclic ring closure of ortho-quinone methides provides a convenient strategy for the synthesis of 277-chromenes. Oxidation of ortho-allylic phenols using DDQ or potassium dichromate is a popular method for the formation of 277-chromenes, via ortho-quinone methide intermediates, and is discussed in detail in the preceding volumes (Scheme 6) <1984CHEC, 1996CHEC-II>. 

Acetoxylation of aromatics (eq. (25)) was first carried out by Davidson and Triggs [92] to produce phenyl acetate, which could give rise to the development of a new phenol synthesis. The formation of phenyl acetate is accompanied by the formation of biphenyl (see Section 3.3.14.7.2). In the presence of oxidants such as Pb(OAc)4, NaN02, NaNOs, KMn04, K2CrOv [93] and P-Mo-V heteropolyacids [94], phenyl acetate is the main product. The favored ring acetoxylation with high-oxidation-state Pd catalyst over dimerization with low-oxidation-state catalyst has recently been confirmed [95]. With toluene, probably in an allylic-like oxidation, benzyl acetate is obtained [92]. 

The synthesis of a variety of other heterocycles has been achieved using similar methodology [108], For example, benzopyran derivatives are readily prepared from 2-allyl phenols [110] note that the Pd( 0) precatalyst is oxidized to Pd(ll) by air before the reaction commences. Nitrogen heterocycles are also accessible from Wacker-type transformations, as demonstrated by the Hegedus indole synthesis described below in Section 1.10. 

Claisen rearrangement of allyl phenolic ethers, followed by oxidation of the alkene generates ortho-hydroxy-arylacetaldehydes which close to give benzofurans under acid catalysis, the example showing the synthesis of 8-methoxypsoralen (33.8.1)7 The formation of 2-substituted benzofurans from 2-(ortho-hydroxyaryl)-ketones is also very easy. ... 

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