Iodobenzoic acids, oxidative addition

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... 

Preparative Methods not commercially available. IBX was first synthesized in 1893, and is the penultimate precursor of the Dess-Martin periodinane reagent. IBX is prepared by the slow addition (0.5 h) of potassium bromate (76.0 g, 0.45 mol) to a rapidly stirred sulfuric acid mixture (0.73 M, 730 mL) containing 2-iodobenzoic acid (85.2 g, 0.34 mol). The reaction temperature is maintained below 55 °C until addition is complete. The reaction mixture is heated to 65 °C for 3.6 h. The flask is cooled to 0 °C, and the solid is filtered and washed with water (1000 mL) and ethanol (2 x 50 mL) to afford IBX in 93-98% yield. An additional ether wash (3 x 50 mL) is beneficial. Other oxidants such as potassium permanganate, chlorine, or oxone can also be employed. 

The facile intramolecular oxidative addition of aryl halide which leads to Pd(IV) complex 22 (see Scheme 2.5) provided the basis for the development ofa special type of Pd(II)/Pd(IV) Heck reaction [58,109]. Although 22 fails to react with methylacrylate at room temperature, an insertion reaction leading to the corresponding Heck product takes place in the presence of AgCl04, which removes a iodide ligand generating the required coordination vacancy. Thus, complex 22 (10 mol%), or its Pd(II) precursor 20, catalyzes a Heck-type couphng of 2-iodobenzoic acid with methyl acrylate, driven by iodide precipitation with silver salts (Eq. (2.10)). The reaction is completed within about 3.5 h at room temperature and, in contrast with the... 

A year later, Blacque and Freeh [24c] performed comprehensive DFT studies on the thermal feasibility of Pd /Pd cycles in pincer-catalyzed Heck reactions and convincingly showed that pincer-type Pd intermediates are indeed thermally accessible with aryl bromides at elevated temperatures and hence are generally to be considered as reactive intermediates in pincer-catalyzed reactions with aryl halides at elevated reaction temperatures (for details, see below). Shortly thereafter, Vicente and coworkers [41] published the first oxidative addition of an aryl iodide on the metal center of a paUadium(II) pincer complex 2-iodobenzoic acid was found to smoothly undergo oxidative addition on the paLladium(II) center of [(ONC)Pd(OAc)]... 

Scheme 10.7 Oxidative addition of 2-iodobenzoic acid on the palladium(ll) center of [(ONC)Pd(OAc)] (18).

Phenyl-1,2-benziodoxole-3(lfJ)-one 131, also known as diphenyliodo-nium-2-carboxylate, is the most common commercially available and practically important representative of arylbenziodoxoles. Phenylbenziodoxole 131 can be prepared by oxidation of 2-iodobenzoic acid with potassium persulfate followed by an addition of benzene according to the optimized procedure pubHshed in Organic Syntheses (Scheme 22 1966OS107). The original procedure was reported in 1960 by Beiinger and Lilhen (1960JA725), and has also been used for the synthesis of the substituted... 

Benzothiazoles have been prepared by oxidative condensation of aldehydes with resin-bound 4-mercapto-3-aminobenzoic acid derivatives (Entry 8, Table 15.18), and by dehydration of 2-mercaptoanilides (Entry 9, Table 15.18). Oxidation of 2,3-di-hydrobenzothiazoles to benzothiazoles can occur spontaneously, without the need of any additional oxidant [231]. Polystyrene-bound 4-iodobenzoate reacts with thiazole in the presence of Pd(0) to yield a 4-(4-thiazoIyl)benzoate (Entry 10, Table 15.18). If Cul is added to the reaction mixture, however, the 4-(2-thiazolyl)benzoate results [141]. 

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