Base forms the β-ketoester enolate. Condensation with formaldehyde and conjugate addition of the second equivalent build a linked diketone intermediate. Intramolecular aldol condensation closes a six-membered ring, and dehydration gives the conjugated cyclohexenone. The retained ester and methyl positions match D; the other drawings place the double bond away from the favoured conjugation or use the wrong substitution pattern.
More Organic Synthesis: Synthesis, reactions, mechanisms and selectivity involving the following classes of compounds – alkenes, alkynes, arenes, alcohols, phenols, aldehydes, ketones, carboxylic acids, esters, nitriles, halides, nitro compounds, amines and amides. Uses of Mg, Li, Cu, B, Zn, P, S, Sn and Si based reagents in organic synthesis. Carbon-carbon bond formation through coupling reactions – Heck, Suzuki, Stille, Sonogashira, Negishi, Kumada, Hiyama, Tsuji-Trost reactions; olefin metathesis, McMurry coupling and Buchwald-Hartwig amination reactions. Baylis-Hillman, Henry, Ritter, Sakurai, Tebbe olefination, Pauson-Khand and Nazarov cyclization reactions. Concepts of multistep synthesis – retrosynthetic analysis, strategic disconnections, synthons and synthetic equivalents. Atom economy and green chemistry, Umpolung reactivity – formyl and acyl anion equivalents. Selectivity in organic synthesis – chemo-, regio- and stereoselectivity. Protection and deprotection of functional groups. Concepts of asymmetric synthesis – resolution (including enzymatic), desymmetrization and use of chiral auxiliaries, organocatalysis. Carbon-carbon and carbonheteroatom bond forming reactions through enolates (including boron enolates), enamines and silyl enol ethers. Stereoselective addition to C=O groups (Cram, Prelog and Felkin-Anh models). Asymmetric aldol reactions – Evans reaction and proline catalyzed reaction. questions
GATE 2019 CY Q48– For the illustrated sequence, identify products P and Q: catalytic Pd(OAc)₂/PPh₃, Ag₂CO₃…
GATE 2019 CY Q51– Cyclohex-2-enone reacts with (CH₃)₂CuLi and then PhSeBr to give P, followed by H₂O₂ to…
