Journal of the American Chemical Society 2002-07-24

GaCl(3)-catalyzed ortho-ethynylation of phenols.

Katsumi Kobayashi, Mieko Arisawa, Masahiko Yamaguchi

Index: J. Am. Chem. Soc. 124(29) , 8528-9, (2002)

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Abstract

Phenols are ethynylated at the ortho position with silylated chloroethyne in the presence of a catalytic amount of GaCl3 and lithium phenoxide. The lithium salt is essential for the catalysis, and addition of 2,6-di(tert-butyl)-4-methylpyridine inhibits desilylation and hydration of the products. The reaction can be applied to various substituted phenols giving the ortho-ethynylated products in high yields, and the turnover numbers based on GaCl3 are between 8 and 10. The reaction mechanism involves addition of in situ formed phenoxygallium to the haloethyne followed by the elimination of GaCl3.