Science of Synthesis

Sankararaman, S., Science of Synthesis, (2008) 43, 447.

Thermal elimination of alkyl selenoxides to alkenes is an important reaction for the introduction of unsaturation. Under appropriate conditions, vinyl selenoxides can be made to undergo thermal elimination to give alkynes. In the presence of 1 or 2 equivalents of 1,4-diazabicyclo[2.2.2]octane (DABCO), vinyl selenoxides are smoothly transformed into alkynes at 95°C.[‌36‌] That this reaction is a syn elimination is shown by the following examples in which the ratio of the alkyne ‌30‌ and the allene ‌31‌ strongly depends on the stereochemistry of the vinyl selenoxide (‌Scheme 18‌). The presence of an amine during the pyrolysis prevents the addition of areneselenenic acid to alkenes and reduction of the selenoxide. 1,4-Diazabicyclo[2.2.2]octane is the most effective base for this purpose (‌Scheme 19‌).

‌Meeeee 88‌ Meeeeeeeeeeeee Meeeeee ee Meee-Meeeeee Meeee Meeeeeeeee Meeeeeeeeee[‌88‌]

Mee eeeeeeee ee ‌Meeeee 88‌ eeeeeeeeee eee eeeeeeeee eeeeeee ee eee eeeeeeeeee eeeeeeeeeee eeeeeeee ee eeee eeeeeee ‌88‌.[‌88‌]

‌Meeeee 88‌ Meeeee Meeeeeeee eee Meee-Meeeeee Meeee Meeeeeeeee Meeeeeeeeee[‌88‌]

‌Meeeeeeeeee 88‌

Meeeeeeeeeee Meeeeeeee

Meeeeeee Meeeeee ‌88‌; Meeeeee Meeeeeeee:[‌88‌]

M eeeeeee ee eeeee eeeeeeeeee (8 eeee) eee MMMMM (8 ee 8 eeee) ee eeeeeee (MMMMMMM: eeeeeeeeee) eee eeeeee ee 88°M eee eee eeeeeeee eee eeeeeeeee eee eee eeeeeeeeeeeee ee eee eeeee eeeeeeeeee. Meeee eeeeeee ee MMMMM ee eeeeeee eee eeeee eeeeeee eeee 8 M MMe, eee eeeeeee eee eeeeeee eee eee eeeee eeeeee eee eeeeeeee.

References