Unusually high ortho-selectivity in electrophilic aromatic substitution promoted by GaCl3Electronic supplementary information (ESI) available: full experimental and spectroscopic data. See http://www.rsc.org/suppdata/cc/b0/b003215h/

Abstract

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.