Advanced Organic Chemistry Practice Problems 2021 Official

Substrate: A linear enynone (R–C≡C–C(O)–CH=CH₂)

Conditions A: Au(PPh₃)Cl (5 mol%), AgSbF₆ (5 mol%), DCM, 25 °C → Furan derivative (major)

Conditions B: PtCl₂ (5 mol%), CO (1 atm), toluene, 80 °C → Phenol derivative (major) advanced organic chemistry practice problems 2021

Question: Propose mechanisms for both pathways. Identify the key intermediates (π-alkyne complex, cyclopropyl metal carbene, etc.) and explain how the metal’s electrophilicity and ligand direct the outcome.

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The problems trending in 2021 moved away from simple functional group transformations. Instead, they emphasized cryptic stereocenters and non-classical carbocations. The problems trending in 2021 moved away from

Instructions: Propose mechanisms, predict major products including stereochemistry, and justify selectivity. Assume standard workup unless stated otherwise.

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Reaction: An enantioenriched chiral phosphoric acid (CPA, 5 mol%) catalyzes the addition of a silyl ketene acetal to an N-Boc isoquinolinium ion generated in situ from 3,4-dihydroisoquinoline and Boc₂O. Reaction: An enantioenriched chiral phosphoric acid (CPA, 5

Observation: The product, a tetrahydroisoquinoline derivative, is formed in 94% ee.

Questions:
a) Draw the transition state model explaining the facial selectivity.
b) How does the counteranion (chiral phosphate) influence the electrophile’s trajectory?
c) If the reaction is run at 0 °C instead of –78 °C, the ee drops to 72%. Why?

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