Yoshiyuki Kido

Aromatic alkenylation using electrophilic organogallium reagent generated from allenylsilane and GaCl3

Abstract Aromatic hydrocarbons are alkenylated with silylallene in the presence of GaCl 3 at −90°C. Organometallic electrophiles generated from the allene and GaCl 3 are the active species in this reaction. A modest level of ortho -selectivity is observed. While the silylallene reacts exclusively at the 2-position, 1,2-alkadiene reacts at the 1-position predominantly.

Unusually high ortho-selectivity in electrophilic aromatic substitution promoted by GaCl3

1,4-Bis(trimethylsilyl)buta-1,3-diyne in the presence of GaCl3 reacts with aromatic hydrocarbons at −90 to −100 °C yielding 2-arylbut-1-en-3-ynes; the reactions exhibit an unusually high tendency to alkenylate the o-position of alkyl substituents; toluene, ethylbenzene and isopropylbenzene react predominantly to exclusively at the o-position while o-xylene and 1,2,3,4-tetrahydronaphthalene react at the 3 and 5-position, respectively.

2,6-Divinylation of phenols with ethyne

Phenols are 2,6-divinylated by treatment with ethyne at 100 °C in chlorobenzene in the presence of SnCl 4 –Bu 3 N, the divinylation occurring predominantly to exclusively with phenol, alkylphenols and alkoxyphenols; an appropriate amount of the tin reagent and the correct reaction temperature are essential for the divinylation.