The products of a chain reaction beginning with acetone and sodium amide
Acetone and sodamide give acetone sodium enolate A, nothing further happens until acetylene is introduced. The pKas of acetone and acetylene are both around 25 so an exchange occurs reforming acetone and creating sodium acetylide. This seems an unusual way of making sodium acetylide, but I don't think this is a real world example (unless someone can find a reference). 

Sodium acetylide adds to acetone giving the sodium alkoxide of tertiary alcohol B

Work up with dilute acid gives the tertiary alcohol C. 

Hydrogenation over Pd catalyst reduces the triple bond to a double bond giving D. 

Passing D over alumina at 400C dehydrates the tertiary alcohol to give isoprene.