Propose a synthesis of but-3-en-1-ol from acetylene.

Solution:
But-3-en-1-ol can be obtained by reaction of the acetylide with oxacyclopropane followed by partial hydrogenation of the alkyne.

[a] : Deprotonation of the alkyne with sodium amide in liquid ammonia
[b] : Nucleophilic attack on oxacyclopropane
[c] : Hydrogenation to alkene with Lindlar's poisoned catalyst.