Diphenyl 2:3:3 :4‘-tetramethoxy

Dibenzoylsinomenolquinone [in, R = < > -CO] can be oxidized by 30 per cent, hydrogen peroxide in hot glacial acetic acid to 4 5 -dimethoxy-5 6 -di(benzoyloxy)diphenic acid [vn, R = CO], hydrolysis and inethylation of which yields 4 5 5 6 -tetramethoxydiphenic acid [vn, R = Me], and decarboxylation of the latter can be effected by boiling with copper powder in quinoline, giving 2 3 3 4 -tetramethoxy-diphenyl[vm] [15], 4 5 5 6 -Tetramethoxydiphenic acid, like 5 6 5 -trimethoxydiphenic acid [16], could not be resolved into optical isomers [15]. 

Also the lithium salts of macrocyclic compounds can be used as C-nucleophiles. Indeed, a new approach to modify the meso-position of tetramethoxy-substituted calix[4]arenes through the direct metal-free C-C cross-coupling of their lithium salts with 1,2,4-triazines has recently been suggested. It has been shown in our laboratory that the carbanions generated from tetraalkoxycalix[4]arenes are able to react easily with 3,6-diphenyl-1,2,4-triazine in THF at —78°C to give the o -adduct at C-6 of the triazine ring. Oxidation of this C-adduct with DDQ at ambient temperature affords meso-substituted calixarene derivatives in good yields (Scheme 40). 

C],H C 0 2.2. Diehlor-4.4 -dloxy-3.6.S. 5 -tetramethoxy-diphenyl 6,1201, II1161. CjgHyCLOs 3.6-Diohlor 2.5.diao8toxy-tare phuialsSure-dikthyiester 10, 557. 

CigHigBrgOg 2.2 -Dibrom-4.4 -dioxy-3.6.3. 6 -tetramethoxy-diphenyl 6,12i01, II1162,... 

Excess chloromethyl ether and HI added to a soln. of 3,4,3, 4 -tetramethoxy-diphenyl sulfide in glacial acetic acid, and the product isolated after 3 hrs. 

CigHigOS, cis-2,4,9-Trimethylthioxanthene 10-oxide, 45B, 382 CigHigOS, cis-9-Ethyl-9-methylthioxanthene lO-oxide, 46B, 363 CigHigOS, cis-9-Isopropylthioxanthene 10-oxide, 41B, 411 CigHig02S2f 2,2-Diphenyl-1,3-dithiane cis-1,3-dioxide, 45B, 383 C1gH1gOftSg, 5,7,14,16-Tetramethoxy-1,2,3,10,11,12-hexathia[3.3]meta-cyclophane, 46B, 363... 

---