# Stepwise Synthesis Solution **Goal:** Synthesize the product from the given starting materials, following the rules stated (no >4C addition at a time, special reagents do not count for Rule 1). ## **Step 1: Alkylation of Acetophenone** ### **Reaction:** Use acetophenone (starting material 1) and react with 1-bromopropane (starting material 2) via **enolate alkylation**. - **Reagents:** 1. Base (e.g., NaOEt or LDA) to generate the enolate from acetophenone 2. 1-bromopropane (propyl bromide) as the alkylating agent ### **Product After Step 1:** You get **1-phenyl-1-butanone**. #### **Explanation:** - The enolate of acetophenone acts as a nucleophile and attacks 1-bromopropane, adding a propyl group to the α-position of the ketone. - This step is valid because you are adding a 3-carbon fragment, which meets the "no more than 4 carbons at a time" rule. --- ## **Step 2: Wittig Reaction to Form Alkene** ### **Reaction:** React 1-phenyl-1-butanone with the Wittig reagent generated from benzyltriphenylphosphonium bromide and base. - **Reagents:** 1. Benzyltriphenylphosphonium bromide (PhCH₂PPh₃⁺ Br⁻) 2. Strong base (e.g., n-BuLi or NaH) to generate the ylide ### **Product After Step 2 (Final Product):** You get **(E)-1-phenyl-4-phenyl-1-butene**, which matches the product shown. #### **Explanation:** - The Wittig reaction converts the carbonyl group to a double bond (alkene), attaching the phenyl group from the ylide at the terminal position. - The "segment" added is a phenylmethylene group, which is allowed under the rules for Wittig reagents. --- # **Final Answer: Full Synthesis Route** 1. **Enolate Alkylation:** Acetophenone + 1-bromopropane + base → 1-phenyl-1-butanone 2. **Wittig Reaction:** 1-phenyl-1-butanone + benzyltriphenylphosphonium ylide → (E)-1-phenyl-4-phenyl-1-butene (final product) --- ## **References for Reaction Types** - **Enolate Alkylation:** Carey & Sundberg, "Advanced Organic Chemistry", Part B, 5th Ed., p. 112 (Alkylation of enolates) - **Wittig Reaction:** Carey & Sundberg, "Advanced Organic Chemistry", Part B, 5th Ed., p. 63 (Wittig Olefination) --- **Summary:** **Step 1:** Alkylate acetophenone with propyl bromide to get 1-phenyl-1-butanone. **Step 2:** Perform a Wittig reaction with benzyltriphenylphosphonium ylide to install the terminal alkene with a phenyl group. **Final Product:** (E)-1-phenyl-4-phenyl-1-butene.