Corey -House synthesis vs Wurtz reaction In Corey House synthesis the first step is formation of Alkyl Lithium. why can't we react alkyl lithium with alkyl halide to produce alkanes. Rather we choose to prepare Gilman's reagent? Does it have something to do with the reactivity of alkyl lithium?
As $\ce{R-Li}$ is very reactive ( even more than $\ce{RMgX}$ ). To decrease the reactivity of $\ce{R-Li}$ , it is reacted with $\ce{CuX}$ to form Gilman Reagent which is less reactive than $\ce{R-Li}$ to produce alkanes. 

If  $\ce{R-Li}$ reacts directly with $\ce{R'-X}$, there will no formation of alkanes, but interchange reaction occurs. 

$$\ce{RLi + R'X --&gt; RX + R'Li}$$