Ml. Spera et Wd. Harman, Osmium-mediated electrophilic addition reactions with selenophene and activation of the Se-C bond, ORGANOMETAL, 18(8), 1999, pp. 1559-1561
The complex [Os(NH3)(5)(eta(2)-selenophene)](OTf)(2) (I) has been prepared
and treated with several electrophilic reagents to afford Se-alkyl and 2H-s
elenophenium complexes in, high yield. In many aspects, the reactivity obse
rved for 1 directly parallels that seen, for the thiophene analogue. Proton
ation (HOTf/MeCN) and alkylation (acetal/TBSOTf) occur at C2, affording (1,
5-eta(2))-2H-selenophenium complexes (2 and 3, respectively). Methylation (
MeOTf/MeCN) occurs at the heteroatom, affording the 1-methylselenophenium c
omplex 4, which, when treated with a nucleophile, undergoes C-Se cleavage t
o form an. eta(2)-4-(alkylseleno)-1,3-butadiene complex (5).