Phenolic ethers Grignard reagents

Aryl-A3-iodanes bearing an electron-deficient alkyl ligand such as aryl(sul-fonylmethyl)-A3-iodanes (Section 3.2.7) and aryl(perfluoroalkyl)-A3-iodanes are relatively stable. A series of (perfluoroalkyl)phenyl-A3-iodanes 96 were synthesized in good yields by treating bis(trifluoroacetoxy)-A3-iodanes with benzene in the presence of triflic acid [47]. The AModanes 96 transfer the perfluoroalkyl groups to a variety of nucleophiles with reductive elimination of iodobenzene. The nucleophiles involve Grignard reagents, alkyllithiums, enolate anions, alkenes, alkynes, trimethylsilyl enol ethers, arenes, phenols, and thiols. In these reactions, the AModane 96 serves as a source of the perfluoroalkyl cation and, in... 

Grignard Reagent pyridinium chlorochromate tosylate protecting group TMS ether Phenols ... 

MetHoxym0thyl ethers of phenols. These ethers are readily prepared by reaction of chloromethyl methyl ether with a suspension of the dry sodium salt of a phenol in benzene or toluene. They are useful as protective groups because they are stable to alkali, to potassium cyanide, to Grignard reagents, and to n-butyllithium, but can be hydrolyzed when desired by very gentle treatment with acid. They are cleaved more easily than the corresponding benzyl ethers. Examples of synthetic uses are as follows. 

The cyclic ether link is activated by the presence of the 6 7-double bond, and desoxycodeine-C will react with Grignard reagents giving phenolic bases probably of the type [xvn] (see Chap. XIX) [11], and with ethyl mercaptan to give ethylthiodihydrodesoxycodeine-C [xvm] [12]. 

Even without the advantage ol a stable earbocation. other ethers may be cleaved under forcing conditions. Simple alkyl ethers lead to mi.vtures including elimination but little substitution, and have little synthetic use. However, aryl methyl ethers may be usefully demethylated to the phenol by heating with Grignard reagents (e.g.. eq. 2.48) 53]. 

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