Which of the following Gilman reagents could be used with a vinyl halide to afford the (E,E)-diene shown below? Select all that apply.
A) I
B) II
C) III
D) IV
E) II and III

Question

Which of the following Gilman reagents could be used with a vinyl halide to afford the (E,E)-diene shown below? Select all that apply.    
A) I 
B) II 
C) III 
D) IV 
E) II and III

Quizplus · Accepted Answer

The (E,E)-diene shown contains two double bonds with E geometry. To achieve this geometry, we need to introduce the two carbon fragments bearing the double bonds from opposite faces of the double bonds in the vinyl halide. The two Gilman reagents that can achieve this are II and III. Option I cannot be used because it can only introduce one carbon fragment at a time. Option IV cannot be used because it would result in the Z geometry for the double bonds. Therefore, the best choice is E, which includes both II and III.

Which of the Following Gilman Reagents Could Be Used with a Vinyl