ABSTRACT A phosphine‐mediated 2+1 annulation of pyrazoloneyldiene oxindoles with α ‐keto esters is reported, enabling modular assembly of oxindole‐cyclopropane‐pyrazolone bispirocycles with excellent chemoselectivity. The reaction proceeds under mild conditions with broad functional group tolerance (including natural product‐derived esters), delivering diverse products in high yields (up to 98%), and is scalable to gram level.
Shen et al. (2026) studied this question.