Advanced Organic Chemistry Practice Problems 2021 //free\\ -

If the 2021 specific set you're looking at has mixed reviews, these are the "Gold Standards" usually recommended by the community: Carey & Sundberg (Part A & B)

A tetracyclic compound with a congested tertiary C–H bond at the benzylic position adjacent to a piperidine ring. advanced organic chemistry practice problems 2021

“Wait, #22… is that a carbene intermediate or not? The 2021 paper says yes, but the problem says prove it.” If the 2021 specific set you're looking at