The cyclization of acetylenic diols I (n = 1, R = R1 = H, RR1 = O) in the presence of HgSO4-H2SO4 gave oxocyclopentanones II (n = 1, R = R1 = H, RR1 = O). Similar reaction of I (n = 2, R = R1 = H) in Me2CO gave a mixture of III, IV and V, but no II (n = 2, R = R1 = H) was observed A mechanism for the formation of IV was proposed.

Key words: CATALYSIS, CYCLIZATION, ALKYNE P, SULFURIC ACID P, MERCURY COMPOUNDS, DIHYDRIC ALCOHOL