Pinacol vinylogous

Due to space limitations, vinylogous reactions of pinacol coupling and reductive coupling using nitriles are not described. Also, reductive coupling reactions between compounds having carbon-carbon multiple bonds and carbonyl compounds are not covered. 

Due to sharp and selective reduction in bond dissociation energy of radical cations [106,107], the cleavage of strong -C-C- or C heteroatom bonds has been observed during PET reactions. In this context, examples of -C-C- bond cleavage from jS-phenylethers [108], bibenzyls and pinacols [25,109,110] may be mentioned. In an extensive study, Whitten et al. [Ill, 112] have reported clean -C-C- bond cleavage from the reaction of /J-aminoalcohols and vinylog-ous amino alcohols. 

Vinylogous pinacol rearrangement j, y- thyleneketones from 2,5-dihydrofurans... 

Scheme 1.8 Use of a vinylogous pinacol rearrangement as part of the total synthesis of ingenol (54). ...

---