Alkyne is a fancy bioisostere of 1,4-disubstituted benzene, so you can exchange the alkyne by a variety of planar aromatic 2,5-disubstituted heterocycles such as furan, pirrol and thiophene. Also, a triazole could be used as bioisostere and can be prepared starting from alkyne and substituted azide using click chemistry.

Gabriel, the (click) triazines are rather ester/amide isosteres.

Cyclopropene could be of interest

May be CN as well

Iodine can be a bioisostere for the acetylene group on an aromatic ring