GaCl3 promotes addition reactions of carbon nucleophiles to a C-C triple bond. Interaction of alkyne with GaCl3 generates a highly reactive electrophile, which aromatic hydrocarbon attacks to give an alkenylated arene. Silylethyne reacts predominantly at the p-position of toluene, while disilylated 1,3-butadiyne exhibits o-selectivity. The behavior of a silylated 1,2-propadiene is intermediate between that of the silylethyne and the disilylated 1,3-butadiyne. In the presence of GaCl3, electrophilic trimerization of silylethyne takes place to give a conjugated hexatriene. In this reaction, silylethyne attacks the GaCl3-activated C-C triple bond. Carbometalation is another interesting addition reaction of an organogallium compound to alkyne. Alkynyldichlorogallium dimerizes in hydrocarbon solvents to give 1,1-dimetallo-1-buten-3-yne. In the presence of GaCl3, silyl enol ether is ethenylated at the α-carbon atom with trimethylsilylethyne. Treatment of lithium phenoxide with silylethyne in the presence of GaCl3 gives o-(β-silylethenyl) phenol. These reactions involve carbogallation of alkynylgallium, gallium enolate, or gallium phenoxide.
|Number of pages||7|
|Journal||Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry|
|Publication status||Published - 2000 Nov|
ASJC Scopus subject areas
- Organic Chemistry