Catechol-ethers

Scheme 22. Triphenylene synthesis by VOC -mediated oxidative coupling of catechol ethers with biphenyls.

At the third stage the dimer catechol ether of monosilicic acid bonded with silica matrix is formed. 

Oxidative cross-coupling of biphenyls with catechol-ethers using FeCly Preparation of 2-hydroxy-3-methoxy-6,7,l0,ll-tetrapeniyloxy triphenylene (384) [37]... 

Oxidative coupling of catechol-ethers with MoCf Preparation of 5,5 -bis(2-chloroethoxy)-4,4 -dimethoxy-2,2 -dimethylbiphenyl (409) [80]... 

Robinson, G. M. Robinson, R. Scission of certain substituted cyclic catechol ethers. J. Chem. Soc., Trans. 1917, 111, 929-940. 

Z iroxyphenoxyaeeiopherume, catechol phenacyl r, phenacyl alcohol catechol ether)... 

Hill GA, RatcUff J, Smith P. Urinary catechol ethers. Chem Ind 1959 399 ... 

The dimethyl ethers of hydroquiaones and 1,4-naphthalenediols can be oxidized with silver(II) oxide or ceric ammonium nitrate. Aqueous sodium hypochlorite under phase-transfer conditions has also produced efficient conversion of catechols and hydroquiaones to 1,2- and 1,4-benzoquiaones (116), eg, 4-/-butyl-l,2-ben2oquinone [1129-21-1] ia 92% yield. 

Both methyl aryl and methyl alkyl ethers are cleaved under these conditions. A methylenedioxy group, used to protect a catechol, is cleaved under similar conditions in satisfactory yield methyl and ethyl esters are stable (0-20°, 2 h). °... 

PROTECTION FOR PHENOLS AND CATECHOLS 24. 4-Picolyl Ether ArOCH2-4-pyridyl (Chart 4) Formation /Cleavage ... 

The cyclohexylidene ketal, prepared from a catechol and cyclohexanone (AI2O3/ TsOH, CH2CI2, reflux, 36 h), is stable to metalation conditions (RX/BuLi) that cleave aiyl methyl ethers. The ketal is cleaved by acidic hydrolysis (coned. HCl/ EtOH, reflux, 1.5 h, 20°, 12 h) it is stable to milder acidic hydrolysis that cleaves tetrahydropyranyl ethers (1 AHCl/EtOH, reflux, 5 h, 91% yield). ... 

Pedersen s preparation of dibenzo-18-crown-6 involves catechol and bis(2-chloroethyl) ether. In this procedure, sodium hydroxide is used as base and M-butanol as solvent. The reactants are heated overnight and the crude crown is obtained by precipitation from acetone in which it is almost completely insoluble. The yield range specified is 39—48% and is readily realized. The overall preparation is illustrated in Eq. (3.11). 

The principal variations on the normal crown synthesis methods were applied in preparing mixed crowns such as those shown in Eq. (3.55) and in forming isomers of the dibinaphthyl-22-crown-6 systems. The latter has been discussed in Sect. 3.5 (see Eq. 3.21) . The binaphthyl unit was prepared to receive a non-naphthyl unit as shown in Eq. (3.57). Binaphthol was allowed to react with the tetrahydropyranyl ether or 2-chloroethoxyethanol. Cleavage of the THP protecting group followed by tosyla-tion of the free hydroxyl afforded a two-armed binaphthyl unit which could serve as an electrophile in the cyclization with catechol. Obviously, the reaction could be accomplished in the opposite direction, beginning with catechol". ... 

The TBDPS ether has been used for the monoprotection of a catechol (TBDPSCl, Im, DMF, 5 h, 83% yield) or simple phenol protection. It is cleaved with Bu4N F- (THF, 94% yield). ... 

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