A Convenient Allenoate-Based Synthesis of 2‑Quinolin-2-yl Malonates and β‑Ketoesters

N-Protected o-aminobenzaldehydes
smoothly react with α,γ-dialkylallenoates under Brønsted
basic conditions to yield 2,3-disubstituted quinolines. This three-step
reaction cascade of Michael addition, aldol condensation, and 1,3-N
→ C rearrangement uses the complete protecting group as a building
block in a highly efficient C,C-bond formation of a new all-carbon
quaternary center. Carbamate protected substrates (N-Boc, N-Cbz, N-Alloc) thus give
2-quinolin-2-yl-malonates, while amide protected substrates (N-Ac, N-Bz) afford 2-quinolin-2-yl-β-ketoesters
in high yields.