Synthesize the following compounds using reactions that are familiar to you. Always choose the highest yielding reaction for each step. Include all pertinent reagents and solvents for each reaction step, and show all created stable intermediate organic compound products $($do not show reaction intermediates such as carbocations or cyclic intermediates$).$

Prepare racemic $1-$cyclopentyl$-1,2-$dideuterioethanol from cyclopentylethyne

Prepare $($E$)-2,3-$dideuterio$-2-$hexene from propyne

Prepare $2,2-$dichloro$-1,1-$diodobutane from ethyne

Prepare $(3$R$,4$S$)-$ and $(3$S$,4$R$)-4-$bromo$-3-$hexanol