Cyclohexanone Synthesis Routes

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Cyclohexanone Reactions & Synthesis i) Synthesis of Methylenecyclohexane from Cyclohexanone Target Compound: Methylenecyclohexane Reaction Type: Wittig Reaction Synthetic Route: Cyclohexanone $\xrightarrow{Ph_3P=CH_2}$ Methylenecyclohexane Mechanism: Ylide attacks the carbonyl carbon of cyclohexanone. Formation of a betaine intermediate. Formation of a four-membered oxaphosphetane ring. Decomposition of oxaphosphetane to yield methylenecyclohexane and triphenylphosphine oxide ($Ph_3P=O$). Reagents: Methylenetriphenylphosphorane ($Ph_3P=CH_2$, Wittig reagent) Typically generated from methyltriphenylphosphonium bromide and a strong base (e.g., n-BuLi or NaH). ii) Synthesis of 1-Methylcyclohexanol from Cyclohexanone Target Compound: 1-Methylcyclohexanol Reaction Type: Grignard Reaction Synthetic Route: Cyclohexanone $\xrightarrow{CH_3MgBr}$ Intermediate Alkoxide $\xrightarrow{H_3O^+}$ 1-Methylcyclohexanol Mechanism: Methyl Grignard reagent ($CH_3MgBr$) acts as a nucleophile, attacking the electrophilic carbonyl carbon of cyclohexanone. The carbonyl $\pi$-bond breaks, forming an alkoxide intermediate. Protonation of the alkoxide by an aqueous acid workup ($H_3O^+$) yields the tertiary alcohol, 1-methylcyclohexanol. Reagents: Methylmagnesium bromide ($CH_3MgBr$) Acid (e.g., $H_3O^+$) for workup iii) Synthesis of Cyclohexanecarbaldehyde from Cyclohexanone Target Compound: Cyclohexanecarbaldehyde Reaction Type: This is more complex and involves multiple steps, likely starting with forming an enamine or similar intermediate. Plausible Synthetic Route (multi-step): Enamine Formation: Cyclohexanone + Secondary Amine (e.g., Pyrrolidine) $\rightarrow$ Enamine Alkylation: Enamine + Bromomethane ($CH_3Br$) $\rightarrow$ Alkylated Enamine (at $\alpha$-carbon) Hydrolysis: Alkylated Enamine $\xrightarrow{H_3O^+}$ 2-Methylcyclohexanone Baeyer-Villiger Oxidation: 2-Methylcyclohexanone $\xrightarrow{mCPBA}$ Lactone Reduction & Oxidation (or other steps): Convert lactone to cyclohexanecarbaldehyde. This is not a direct conversion and is a less straightforward synthesis from cyclohexanone to cyclohexanecarbaldehyde. A more direct route to a cyclohexanecarbaldehyde would typically involve starting from a cycloalkene or modifying existing substituents. Note: Direct conversion from cyclohexanone to cyclohexanecarbaldehyde is not trivial. The structure shown (cyclohexane ring with a -CHO group attached) implies adding a carbon atom and then oxidizing it. Alternative approach for -CHO group: Grignard Reaction: Cyclohexylmagnesium bromide (from bromocyclohexane) + Ethylene oxide $\rightarrow$ Primary alcohol Oxidation: Primary alcohol $\xrightarrow{PCC}$ Cyclohexanecarbaldehyde However, the question specifies starting from cyclohexanone. A chain extension and oxidation is needed. A more direct route from cyclohexanone to a cyclohexyl aldehyde would be to convert it to its enolate, react with a one-carbon electrophile, and then reduce the carbonyl and modify. This is a complex transformation. Let's consider a route involving homologation and oxidation: Wittig Reaction: Cyclohexanone $\xrightarrow{Ph_3P=CH-OCH_3}$ Enol Ether Hydrolysis: Enol Ether $\xrightarrow{H_3O^+}$ Cyclohexanecarbaldehyde (via hydrolysis of the vinyl ether) Reagents (for Wittig-hydrolysis route): Methoxymethylenetriphenylphosphorane ($Ph_3P=CH-OCH_3$) Acid (e.g., $H_3O^+$) for hydrolysis