2-Iodobenzo furan

As shown in Equation (83), 2-iodobenzo[ ]furan was also prepared by reaction of benzo[, ]furan 82 with tert-butyllithium in ether at -78 °C, followed by reaction with iodine <2002JOC7048>. 

Treating 2-furyltithium (derived from deprotonation of furan with n-BuLi) with ZnCh gave 2-furylzinc chloride, which then was coupled with 1,3-dibromobenzene to furnish bis-furylbenzene 12 [20, 21]. In addition, 2-furylzinc chloride was coupled with 4-iodobenzoic acid to give adduct 13. The Negishi reaction conditions were compatible with the carboxylic acid [22],... 

Synthetic procedures are available for the preparation of fluoro (e.g., 2-lithio-l-methyl-5-octylpyrrole with fV-fluoro-iV-(phenylsulfonyl)benzenesulfonamide <2003JFC(124)159>), chloro, bromo, and iodo compounds from the corresponding lithio derivatives, for example, 2-iodobenzo[A]furan via lithiation of the heterocycle then reaction with iodine <2002JOC7048>. Perchloryl fluoride (FCIO3), A-chlorosuccinimide, bromine, and iodine are examples of reagents which can be used to introduce fluorine, chlorine, bromine, and iodine, respectively. 

This may imply that the intermolecular coupling of various aryl halides with other heteroaromatic compounds may proceed. Indeed, it is now known that not only the special heteroaromatic halides but also usual aryl halides can react with a variety of five-membered aromatic heterocycles, including furans, thiophenes, and azole compounds such as M-substituted imidazoles, oxazoles, and thiazoles [133-137]. The arylation of azoles can be carried out using iodobenzoate immobilized on an insoluble polymer support [138]. Related intermolecular reactions of indole [139] and imidazole [140] derivatives have also been reported. 

The coupling cyclization of 3-deuterated 1,2-decadienyl methyl ketone with iodobenzoate under the conditions A afforded nondeuterated 2,3,5-trisubsti-tuted furans in 89% yield (Scheme 7). Furthermore, t-butyl 1,2-decadienyl ketone can also undergo coupling cyclization with Phi under the conditions A... 

Different heteroaromatic rings (e.g., pyridine, furan and thiophene) and carbon-carbon double bonds are well tolerated under the reaction conditions. Moreover, reagent 130 can be easily recycled from the reaction mixture and reused. The mechanism of this reaction includes initial homolytic cleavage of the I—Cl bond providing a chlorine atom and the iodanyl radical 132, which is in equilibrium with the benzoyloxy radical 133. TEMPO (134) is oxidized by the chlorine atom to oxoammonium salt 135, which then oxidizes the alcohol 129 to the corresponding carbonyl compound 131 and is itself reduced to hydroxylamine 136. The benzoyloxy radical 133 accomplishes the regeneration of TEMPO 134 from hydroxylamine 136, giving rise to 2-iodobenzoic acid and the catalytic cycle is complete (Scheme 3.55) [158]. 

A palladium(ll) catalyst promoted condensation of an Al-aryl imine and an alkynylbenzodioxolone derivative to afford a multi-substituted furan, with substituents derived from the alkynyl moiety (2-position), the imine (3- and 4-positions), and the 2-iodobenzoate moiety (5-position), along with an N-arylformamide under mild conditions (14JA11598). 

Radical Substitution.—The reactions of 3-benzo[6]thienyl radicals generated by the photolysis of 3-iodobenzo[Z>]thiophen have been studied in a variety of monosubstituted benzenes as solvent. Isomer ratios were determined, and the results indicate that the 3-benzo[6]thienyl radical has a reactivity intermediate between those of 2- and 3-thienyl radicals. The homolytic phenylations of benzo[6]thiophen and benzo[6]furan have been compared. Thermal decomposition of )V nitrosoacetanilide was the source of phenyl radicals. Whereas homolytic substitution in benzo[6]-furan occurs almost exclusively in the heterocyclic ring, benzo[6]thiophen shows comparable reactivity in all positions. The synthesis of all six isomeric phenyl benzo[6]thiophens is given. ... 

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