Substitution of the Phenolic Ether Group

Dealkoxylation is also closely related to substitution of the phenolic ether group which is considered in the next section. 

Grignard reagents have been used traditionally as somewhat crude demethylating agents but in the following example demethoxylation was effected in preference to attack of the reagent at the hindered ester site. A 2 1 mixture of phenyl magnesium bromide and 2,6-di-tert-butyl-4-methylphenyl 

2-methoxybenzoate in benzene/ether (2 1) during 6 hours at ambient temperature furnished the 2-phenyl derivative shown in 96% yield. The % yield was influenced by the degree of hindrance in the ester (ref. 100). 2-Methylphenyl magnesium bromide has also been employed for the 2-methyl analogue of interest in synthetic work on cannabinoids (ref. 100a). 

Conventionally phenyl tetrazolyl ethers have been employed for the removal of an OH group. Addition of a mixture of an ethereal solution of phenyl 5-(1-tetrazolyl)ether and a catalytic amount of dichloro[1,3-bis(diphenyl-phosphino)-propane]nickel(ll) introduced dropwise into refluxing sec-butyl-magnesium chloride under nitrogen followed by reaction for 10 minutes afforded upon work-up,sec-butylbenzene in 77% yield (ref. 101). 

9-Methoxyanthracene in benzene with 1-butylthiol and a little methanesuiphonic acid after refluxing for 15 hours gave 9-anthryl n-butyl sulphide in 85% yield (ref. 102). 

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