Benzo thiophenes selenium derivatives

The orf/zo-alkenylarylzinc reagent obtained by the migratory arylzincation serves as a precursor to benzo[ijchalcogenophenes such as benzo[fe]thiophenes and benzo[h]selenophenes (Scheme 10.9) [28]. Treatment of the zinc intermediate with sulfur powder in the presence of Cul allows one-pot synthesis of a benzo[h]thiophene derivative (route A). Alternatively, the zinc intermediate is quenched with iodine to give ortho-alkenylaryl iodide, which is then subjected to copper-catalyzed reaction with sulfur or selenium powder to furnish the corresponding benzo[i]thiophene or benzo[(i]selenophene derivative (route B). Collectively, these approaches allow for expedient synthesis of functionalized benzo[h]thiophenes and benzo[()]selenophenes, many of which are difficult to... 

Attempts to correlate the position of the substituent with the UV spectrum have been largely unsuccessful, but some general comments may be made. The spectra of most monosubstituted derivatives resemble that of benzo [6]thiophene and the three distinct zones usually remain. Methyl or halo substituents cause an overall bathochromic shift relative to benzo [6]thiophene—zone B is most affected by 3-, 5-, or 6-substituents zone C by 5-substituents.134,159,162 3-Alkyl-benzo[6]thiophenes are characterized by zone-B bands of lower intensity than those of benzo [6]thiophene and its other alkyl derivatives.134 The UV spectra of 2-methylbenzo[6]thiophene and its selenium analog have been compared.182... 

The UV spectra of benzo[6]thiophene-4,7-quinone and its 5-hydroxy derivative have been compared with those of their oxygen and selenium analogs.195... 

A review entitled thiophenes from Viktor Meyer to Poly (thiophene) some reactions and synthesis was published in a special issue of Phosphorus, Sulfur and the related elements (13PS287). Over 80 reaction schemes are presented outlining important discoveries in the chemistry of thiophenes. Another review generalized published data on the reactions of 4-(2-R-aryl)-1,2,3-thia- and selenadiazoles (13RJOC479). Special emphasis on the use of these selenadiazole for the synthesis of 1-benzothiophenes, 1-benzosele-ophenes, and their more complex derivatives was presented. A recent review on recent advances in the use of the Wfllgerodt-Kindler reaction in thiophene syntheses appeared this year (13CSV7870). Extensive reviews on selenium and tellurium chemistry from small molecules to biomolecules and materials (B-13M001) as well as data on the synthesis, reactions, crystal structures, and spectral characteristics of benzo[b]tellurophene, dibenzo[b,d]... 

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