Let's break down each synthesis sequence **step-by-step**, showing **the product after each step** and **explaining** the transformations. --- ## **1. Synthesis 1** **Starting material:** 4-hydroxy-2-oxopentanoic acid ethyl ester ### **Stepwise Reactions:** 1. **TBDMSCl, Imid** - **Protect the alcohol** as a TBDMS (tert-butyldimethylsilyl) ether. - **Product:** Ethyl 4-(TBDMSO)-2-oxopentanoate 2. **NaBH₄, EtOH** - **Reduces ketone to secondary alcohol.** - **Product:** Ethyl 4-(TBDMSO)-2-hydroxy-pentanoate 3. **Ph₃P=CH₂ (Wittig reaction)** - **Converts the ester to a terminal alkene.** - **Product:** 4-(TBDMSO)-2-hydroxy-1-pentene 4. **Phenylmagnesium bromide (XS, Grignard)** - **Adds phenyl group to the secondary alcohol carbon (now a ketone or aldehyde carbon after step 3).** - This step is ambiguous, but likely adds to a carbonyl if present. However, after Wittig, there is no carbonyl. This may be a mistake or refers to another intermediate. - **Assume it adds to the alkene via an addition/elimination sequence, forming a tertiary alcohol.** - **Product:** 4-(TBDMSO)-2-hydroxy-3-phenyl-1-pentene (with tertiary alcohol at C3) 5. **TBAF (tetrabutylammonium fluoride)** - **Deprotects the TBDMS group.** - **Product:** 4-hydroxy-2-hydroxy-3-phenyl-1-pentene 6. **PCC** - **Oxidizes the secondary alcohol (C2) to a ketone.** - **Product:** 4-hydroxy-2-oxo-3-phenyl-1-pentene 7. **DDQ** - **Oxidizes the benzylic alcohol to a quinone or forms a conjugated system.** - The most likely effect is to oxidize any benzylic alcohol or ether, but with the structure above, there may not be a direct reaction unless there is a benzylic position. - **Product:** This step may not alter the structure further if there's no benzylic alcohol. --- ### **Summary for 1:** **Final product:** 4-hydroxy-2-oxo-3-phenyl-1-pentene --- ## **2. Synthesis 2** **Starting material:** 1-butanol ### **Stepwise Reactions:** 1. **PBr₃** - Converts 1-butanol to 1-bromobutane. 2. **Mg** - Forms 1-butylmagnesium bromide (Grignard reagent). 3. **K₂Cr₂O₇, acetone, H₂SO₄** - Not used here; this is for oxidations. 4. **Cyclohexylmagnesium bromide** - Not used yet. 5. **TBSCl, imid.** - Protects OH, but not needed for this chain. 6. **KCN, DMSO** - Nucleophilic substitution: Br replaced by CN (if not Grignard). But we've made Grignard. 7. **B(OMe)₃, H₂O₂** - For hydroboration/oxidation. 7a. **THF/H₂O** - Quench Grignard. 7b. **H₂O₂, NaOH** - Used in hydroboration/oxidation. Let's interpret: - **1. PBr₃:** 1-butanol → 1-bromobutane - **2a. Mg:** 1-bromobutane → 1-butylmagnesium bromide - **2b. (Not clear, possibly use Grignard on a carbonyl)** Since no electrophile is given, let's pair with **step 4**: - **Reaction between 1-butylmagnesium bromide and cyclohexanone (step 4, if that's the intent; cyclohexylmagnesium bromide would react with something else)** Assume addition of Grignard to cyclohexanone: - **Product:** 1-butylcyclohexanol (secondary alcohol at the ring) --- ### **Summary for 2:** **Final product:** 1-butylcyclohexanol --- ## **3. Synthesis 3** ### **Stepwise Reactions:** **Starting material:** Cyclopentanone 1. **LiAlH₄** - Reduces ketone to secondary alcohol (cyclopentanol) 2. **PBr₃** - Converts alcohol to bromide (bromocyclopentane) 3. **IDA (sodium iodoacetate?)** - Substitutes Br with I (iodocyclopentane) **Intermediate A:** Cyclopentyl iodide **Side sequence:** MMPP (oxidant) Forms **epoxide** (if the starting material was an alkene). If not, this may be for a later step. **Intermediate B:** Cyclopentyl magnesium bromide (Grignard reagent) **Final:** Add B (Grignard) to A (cyclopentyl iodide)—**Wurtz-type coupling**. **Final product:** Dicyclopentyl (C₅H₉–C₅H₉) --- ## **Summary Table** | Step | Main Transformations | Product | |------|---------------------------------------------|-----------------------------------| | 1 | Protect OH, reduce ketone, Wittig, Grignard, deprotect, oxidize | 4-hydroxy-2-oxo-3-phenyl-1-pentene | | 2 | PBr₃, Mg, Grignard to carbonyl | 1-butylcyclohexanol | | 3 | Reduce, halogenate, Grignard, couple | Dicyclopentyl (C₅H₉–C₅H₉) | --- ### **If you need detailed structures or mechanism diagrams, please let me know!**