Cyclisation of 2-methylbut-3-yn-2-01 to mainly 1,2,4-tris(l -hydroxy-I -methylethyl) benzene occurs using as catalysts (a) tricarbonylnitrosylcobalt(0). (b) three-component catalytic systems containing sodium borohydride, a cobalt(r1) salt, and a third component such as nitric oxide (or ions such as NO,-. NO,-, etc.), and (c) cobalt(l1) 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(l -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(l1) salt, and triphenylphosphine, and (c) a nickel(i1) derivative such as Ni(CN)2, Ni(OEt),, etc., in the presence of triphenylphosphine. Propargyl alcohol is cyclised by the same catalytic systems to aromatic compounds, but with less steric selectivity.
Milanese, MilanTHE acetylenic alcohol 2-methylbut-3-yn-2-01 (I) is reported to polymerise in the presence of dicarbonylbis (triphenylphosphine)nickel(O) to give only 1,3,5-tris-(l-hydroxy-l-methylethy1)benzene (11), although the corresponding 1,2,4-~ubstituted benzene ( 111) is also possible. However, later workers were able to identify
