0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via C—C Bond Forming Reactions

DOI: 10.1055/sos-SD-234-00262

Bietti, M.; Dénès, F.Science of Synthesis: Free Radicals: Fundamentals and Applications in Organic Synthesis, (20211547.

Toluene and related aromatic compounds possessing benzylic CH bonds add to dimethyl fumarate, fumaronitrile, and 1,4-diphenylbut-2-ene-1,4-dione upon initiation with triethylborane (Scheme 73). The reaction is usually complete within 3 hours at 180 °C, in diluted solution (c = 0.01 M; to minimize the competing polymerization process), and requires only 0.3–1 equivalents of triethylborane. In the absence of triethylborane the adduct is still formed, albeit in very low yield (ca. 8%), indicating that the reaction can be initiated by traces of impurities, presumably peroxides or molecular oxygen.[‌182‌] Under these conditions, reactive oxygen-centered species generated by reaction between triethylborane and molecular oxygen are believed to initiate the reaction by abstracting a hydrogen atom from the benzylic position. The benzylic radical formed adds to the radical trap and the resulting electrophilic radical intermediate is proposed to propagate the chain by playing the role of the hydrogen-atom-abstracting species as it is not able to react with trialkylborane, unlike radicals resulting from the addition to enones.

Meeeee 88 Meeeeeeeeeeeee-Meeeeeee Meeeeeeeee ee Meeeeeee Meeeeeeee[‌888‌]

Meeeeeeeeee 88

M8 M8 M8 M8 M8 Meeee (%) Mee
MMe M M M MM8Me 88 [‌888‌]
M MMe M M MM8Me 88 [‌888‌]
M M MMe M MM8Me 88 [‌888‌]
MMe MMe M M MM8Me 88 [‌888‌]
Me M M M MM8Me 88 [‌888‌]
M Me M M MM8Me 88 [‌888‌]
M M Me M MM8Me 88 [‌888‌]
M M M M MM8Me 88 [‌888‌]
M M M Me MM8Me 88e [‌888‌]
MMe M M M MM >88 [‌888‌]
MMe M M M Me 88 [‌888‌]

e Meeeeee ee eeeeeeeeeeeee (ee 8:8).

Mee eeeeeeeee eeeeeeeee ee Meeeeee, Meeeeeeee, ee ee. (eee Meeeeee ee eeeeeee MM eeeeeeeeee eeeee eee eeeeeee ee eeeeeeeee-eeeeee-eeeeeee eeeeeeee eeeeeeee eeee eee eeee ee eeeeeee(MMM) eeeeeeeeeeeee 88 eee e eeeeeeeee eeeeeeeee eeee eeeeeeeeeee eeee eeee MMMe eeeeee eee eee eeee-eeeeeeeee MM eeee eeeeeeeeee ee eeeeeeee eeeeeeeee ee eee eeeeeeee ee eeeee eeeeeeee MM eeeee, eeee ee eeeeeeee M(ee8)M eeeee. Meeeeeeeeeeee, eeeeeeeeeee eee ee eeeeeeee eeee eeee eee eeeeeeee eeeeeeeee eee eeeeeee, eeee MMM eeeeee eeeee eeeeeeeeeeeeee ee eee eeee eeeeeeee-eeee eeeeeeee ee eee eeeeeeeeee ee eeeeeeeeeeeeee 88 (Meeeee 88).[‌88‌]

Meeeee 88 Meeeeee ee Meeeeeeee Meeeee-Meeeeee Meeeeeee Meeeeeee Meeeeee ee MM Meeeeeeeee ee Meeeeeee Meeeeeeee[‌88‌]

Mee Meeeeee eeeee eeeeeeeeeeee ee eee eeee 8888e eeee eeeeee eeee eeeeeeeeee eeeeee MM eeeee, eeee ee eeeeeeeeeeee eee eeeeeeeeeeee (e.e., eee-eeee-eeeeeeeeeeeeeeeee ee eeeeeeeeeeeeeeeeeeee) eee eeeeeeeee eeeeeeee-eeeeeeee eeeeeeeee[‌88‌] eeeeeee ee eeeeeeeeeeee e eeeee ee eeeeeeeeeeeeeee eeeee eeee MM eeee eeeeeeeeee eeee e eeeeeee ee eeeeeeeeee.[‌888‌‌888‌]

Meeeeeeee eeee eeeeeeeeee eeee, eee MeeMeeeee eeeee eeeeeeee ee 8888 e eeeeeeeee eee eee eeeeeeeee ee eeeeeee M(ee8)M eeeee, eeeee eeeeeeee e eeeeeeeeee eeeeeeee eee e eeeee, eee eeee ee eeeee ee ee eeeeeeee ee eeeeeeeeeeeee eeeee eeeeeee ee eeeeeeee eee eeeeeeee eeee eeee eee eeeeeee eeeeeeee (Meeeee 88).[‌888‌] Mee eeeeeeeee ee eeeeee eee eeeeeee eeeeeee ee eeeeeee eee eeee eeeeeeeeeee eeee eeeeeee eeeee (88-M MMM), ee eee eeeeeeee ee eeeeeeeee eeeeeee ee eeee eeee[8-(8-eeeeeee)eeeeee]eeeeeee(MMM) [Me(eee)8)] eee eeeeeeeeeeeeeeeeeeeeeee, eeeeeeeee eeeeeeeee, eee e eeeeeeeeee eeeeeeeeeee eeee ee eeeeeeee-eeeeeeeeeee eeeee ee e eeeeeee eeee (8.88-eeee eeeee). Mee eeeeeeee eeeeeeee ee eeeeeeee ee eeee eeeeee eee eeee eeeeeeee eeeeee ee eeee- eee eeeeeeeeeeeeeeeee (eeee eeeeeeeeeee eeee 8:8 ee >88:8) ee eee eeeeee ee eeeeeee eee eeeee eeeeeeeeee eeeeeeeeee eeeee. Meeee eeeeeee eee eeeeeee MMM ee eee eeeee eeeeeee eeee eeeeeeeeeeeeee eeeeeee, eee eeeeeeee ee eee eeeeeee eeeeeee eeee eeeeeeeeeeeeee eeeeeee eeeeeeee eee eeeeeeee, eee MM eeee eeeeeeeee eeee eeeeee eeeeeeeeeee eeeeeee eee eeeeeee, eee eee eeeeeeeeeeeee ee eee eeeeeee M=M eeee. Meeeeeeeeeeeee eee eeeeeeee eee ee eeeeeeeee eeee eee eeeeeeeeeeeee eeeee eeee eeeeee eee eeeee eeeeee eeeeeee, eeeeeeeeeeee, eee ee eeeee eeee eeeeeeee ee ee eeeeeeee ee eeeeeeeee ee eeee eeeee β ee e eeeeeeee.

Meeeee 88 Meeeeeeee ee ee Meeeeee Meeeee eeee Meeeeeeeeeeeeeeeee[‌888‌]

M eeeeeeeee eeee eeeeeee ee eeee eeeeeeee ee eee eeee eeeeeee eee eee eeeeeeeee ee eeeeee eeeeee[‌888‌] (eee Meeeee 88, Meeeeee eeeeeeee eee eee eeeeeeeee ee eee eeeeeeee eeeeeee (Meeeee 88).

Meeeee 88 Meeeeeee Meeeeeeee eee Meeeeeeee ee Meeeeee Meeeeeeee[‌888‌]