Selenophenes 500 Subject

Dr. S. T. Reid has contributed the first of two sections on photochemistry of heterocycles, the present one dealing with that of /V-heterocycles. This updates part of his own earlier review The Photochemistry of Heterocycles published in 1970 in Volume 11. A further contribution, which will extend the updating to O- and 5-heterocycles, should be published shortly. Dr. A. B. Hornfeldt s review, entitled Selenophenes, also deals with a subject that was previously reviewed in Volume 12 of this series by N. N. Magdesieva. 

The tetrahydro derivatives of selenophene and tellurophene have also been the subject of full vibrational studies which led to satisfactory assignments only if non-planar conformations with C2 symmetries were assumed (77SA(A)1083>. 

MBH adduct 842 has subjected to epoxidation with m-CPBA followed by a Swern oxidation to afford aldehyde 844 (Scheme 4.244). Wittig methodology using (iodomethylene)triphenylphosphorane gave iodide 845 in 34% overall yield. Iodide 845 was subsequently treated with sodium benzylselenoate to afford 846 and then free-radical mediated ring closure as well as ester hydrolysis afforded selenophene-3-carboxylic acid 847 in 26% yield within two steps. Acid... 

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... 

---