Diphenyliodonium carboxylates

A further solution to the problem of isomer formation in the synthesis of oxoacridine carboaylic acids is to mask one of the two carboxyl groups. The requisite 2-(2-metho carbonylphet lamino)benzoic acids are available from methyl anthranilates reaction with diphenyliodonium carboxylates. The esters which result after cyclisation with polyphosphoric ethyl ester undergo ready alkaline l drolysis to the acid (G.W. Rewcastle and W.A. Denny. Synthesis. 1985. 220). 

When the synthesis of the appropriately substituted anthranilic acid cannot be achieved by the usual Jourdan-Ullmann method, the reaction of an aniline with diphenyliodonium carboxylate in the presence of... 

Diethylammonium chloride, reaction with chloroform to give 1,1,3-trichloro- -nonane, 45,104 Diethylazelate, 46, 31 Diethylbenzene as solvent for decomposition of diphenyliodonium-2-carboxylate in preparation of... 

With benzenediazonium-2-carboxylate or diphenyliodonium-2-carboxylate monohydrate, benzyne precursors, 11 yield 1818 (Scheme 34). 

DiphenyI-3-ethylpentane, 48, 82 Diphenyliodonium-2-carboxylate, as reagent for generation of benzyne,... 

Sodium, with l-bromo-3-chloro-cyclobutane to give bicyclo [l.l.O]butane, 51, 55 Sodium amalgam, 50, 50, 51 Sodium amide, with 2,4-pentane-dione and diphenyliodonium chloride to give l-phenyl-2, 4-pentanedione, 51, 128 Sodium azide, 50, 107 with mixed carboxylic-carbonic anhydrides, 51, 49 Sodium borohydride, reduction of erythro-3-methanesulfony-loxy-2-butyl cyclobutanecar-boxylate, 51, 12 reduction of 2-(1-phenylcyclo-pentyl)-4,4,6-trimethyl-5,6-dihydro-1,3(4H)-oxazine to 2-(1-phenylcyclopentyl)-4,4, 6-trimethyltetrahydro-l,3-oxazine, 51, 25 Sodium cyanoborohydride, used... 

Benzyne, generated from diphenyliodonium 2-carboxylate, reacts with various thiophenes by addition to the sulfur and (3-carbon to give, after loss of an acetylene moiety, benzo[/j] thiophenes in low (< 4%) yield (Scheme 44) (81CC124). 

The first successful Diels-Alder addition of thiophene appears to have been with tetrafluorobenzyne (66CC143). The adduct apparently loses sulfur, resulting in the isolation of the tetrafluoronaphthalene in 40% yield (Scheme 78). Other thiophene derivatives (69T25) and fluorinated benzynes <71JCS(C)604) have been similarly reacted. Subsequently it was found (80H 14)647) that unsubstituted benzyne, generated from diphenyliodonium-2-carboxylate, could be trapped with thiophene to form naphthalene in 33% yield. The earlier failure to add thiophene to benzyne generated by other methods must have been due to intervention of side reactions. Thiophyne also has been similarly trapped to yield benzo[A]thiophene (see Section 3.14.2.2). 

A. Diphenyliodonium-2-carboxylate. An Erlenmeyer flask containing 80 ml. of concentrated sulfuric acid (Note 1) is placed in an ice bath to cool. To a 2-1. three-necked flask are added (Note 2) 20 g. (0.081 mole) of lump-free o-iodobenzoic acid (Note 3) and 26 g. (0.096 mole) of potassium persulfate (Note 4.) The flask is cooled in an ice bath, the chilled sulfuric acid is added, and the flask is swirled in an ice bath for 4-5 minutes to produce an even suspension and to control the initial exothermal reaction. The flask is then removed from the ice bath and the time is noted. 

Two polyvalent iodine compounds arising from o-iodobenzoic acid have been found to be useful synthetic reagents. Thus oxidation of the iodo acid (7) with potassium persulphate, followed by the addition of benzene and treatment with potassium iodide gives the iodonium iodide (8) which is converted into diphenyliodonium-2-carboxylate [DPIC (9)] with aqueous alkali (Expt 6.35).16... 

Benzyne is an important reactive intermediate especially useful for the construction of polycyclic compounds via cycloaddition reactions with various dienes. Several benzyne precursors, including diphenyliodonium-2-carboxylate [ 1 ], have been previously used for the generation of benzyne by thermal decomposition. More recently, several new precursors that generate benzyne quantitatively under very mild conditions have been developed [105 -108]. An efficient benzyne precursor, iodonium triflate 109, can be readily prepared by the reaction of l,2-bis(trimethylsilyl)benzene 108 with [(diacetoxy)iodo]benzene in the presence of trifluoromethanesulfonic acid (Scheme 47) [105]. 

Diacetoxyiodo)benzene Aldrich, Fluka, Lancaster, Merck [Bis(trifluoroacetoxy)iodo]benzene Aldrich, Fluka [Bis(trifluoroacetoxy)iodo]pentafluorobenzene Aldrich, TCI America Iodosobenzene ICN, TCI America 2-Iodosobenzoic acid Aldrich, Fluka [Hydroxy(tosyloxy)iodo]benzene Aldrich Diphenyliodonium-2-carboxylate Lancaster... 

This new benzyne precursor combines practical facility in its preparation with relative stability and safety in handling in addition, its conversion into benzyne does not require a strong base or high temperature. Another useful feature of this methodology is that, as with substituted diphenyliodonium 2-carboxylates, only one aryne can be formed from substituted precursors. Indeed, two methyl analogues of 2-trimethylsilyl-diphenyliodonium triflate, in the presence of furan, afforded quantitatively the corresponding adducts high yields of benzyne-diene adducts were also obtained with other 1,3-dienes. 

The arylation of nitrite and azide anions as well as some amines can be of synthetic interest in some instances for example, difuryl, dithienyl and diselenophyl iodonium salts were useful substrates for the preparation of the corresponding nitro heterocycles [61]. Diphenyliodonium 2-carboxylate transferred its carboxy-late-bearing ring with high specificity to several anilines in a reaction especially suitable for the preparation of weakly basic and sterically hindered A-arylanthranilic acids. 

A solution of diphenyliodonium 2-carboxylate (2.0 g, 6.18 mmol), 2,3-dimethylani-line (0.90 g, 7.4 mmol) and cupric acetate (40 mg) in 2-propanol (8 ml) was heated under reflux for 15 h. The mixture was concentrated and taken up in dilute sodium hydroxide solution. After ether extraction and filtration of the aqueous phase, the filtrate was added slowly to acid to give iV-(2,3-dimethylphenyl)anthranilic acid (1.45 g, 97%), m.p. 220-222°C. 

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