REARRANGEMENT OF 1,5-HEXADIYNE AND 1,6-HEPTADIYNE

The rearrangement of 1,5-hexadiyne (I) with potassium t-butoxide in t-butyl alcohol led mainly to a ca. 2:1 mixture of cis-1,3-hexadien-5-yne (IVa) and trans-1,3-hexadien-5-yne (IVb), and a minor amount of 2,4-hexadiyne (II). Both IVa and IVb were isolated and characterized. Contrary to previous reports, a similar result was obtained when the rearrangement of I was carried out with ethanolic potassium hydroxide, and in this case 2-ethoxy-2-hexen-4-yne (VIa) (derived from II) was also formed. The rearrangement of 1,6-heptadiyne (VIII) with potassium t-butoxide in t-butyl alcohol gave toluene and trans-1,3-heptadien-5-yne (Xb) in about equal amounts, but no cis-1,3-heptadien-5-yne (Xa) was detected. Authentic samples of Xa and Xb were prepared by methylation of IVa and IVb. © 1969.