Cyclisation of 2-methylbut-3-yn-2-ol. Part I. Cyclisation to aromatic compounds

Abstract

Cyclisation of 2-methylbut-3-yn-2-ol to mainly 1,2,4-tris(1-hydroxy-1-methylethyl)benzene occurs using as catalysts (a) tricarbonylnitrosylcobalt(0), (b) three-component catalytic systems containing sodium borohydride, a cobalt(II) salt, and a third component such as nitric oxide (or ions such as NO₃-, NO₂-, etc), and (c) cobalt(II) acetylacetonate in the presence of nitric oxide; suggesting that these three apparently different catalyst systems are equivalent.

In the same way a mixture containing mainly 1,3,5-tris(1-hydroxy-1-methylethyl)benzene and linear trimers is obtained using (a) carbonyltriphenylphosphinenickel(0) compounds, (b) a three-component catalytic system containing sodium borohydride, a nickel(II) salt, and triphenylphosphine, and (c) a nickel(II) derivative such as Ni(CN)₂, Ni(OEt)₂, etc., in the presence of triphenylphosphine. Propargyl alcohol is cyclised by the same catalytic systems to aromatic compounds, but with less steric selectivity.