We have isolated the sulfonylbuta-1,3-diynes 3 and 5 as colorless prisms, which demonstrate unprecedented dimerization. Furthermore, the reactions of 3 and 5 with alkoxides or buta-1,3-dienes were examined and the products obtained were either sulfonyl-β-alkoxybut-1-en-3-ynes 16a–e, β-alkoxybut-3-en-1-ynes 17a–d or the cycloadducts 23 and 24a,b.