Chapter 8, Problem 1LGP

(a) Synthesize (3S, 4R)-3, 4-dibromo-1-cyclohexylpentane (and its enantiomer, since a racemic mixture will be formed) from ethyne, 1-chloro-2-cyclohexylethane, bromomethane, and any other reagents necessary. (Use ethyne, 1-chloro-2-cyclohexylethane, and bromomethane as the sole sources of carbon atoms.) Stan the problem by showing a retrosynthetic analysis. In the process, decide which atoms of the target molecule will come from which acorns of the starting reagents. Also, bear in mind how the stereospecificity of the reactions you employ can be used to achieve the required stereochemical form of the final product.

(b) Explain why a racemic mixture of products results from this synthesis.

(c) How could the synthesis be modified to produce a racemic mixture of the $\left(3\text{R},4\text{R}\right)$ and $\left(3\text{S},4\text{S}\right)$ isomers instead?