Formal [3+3] Cyclization Between 3‐Alkynyl‐3‐hydroxyisoindolinones and Substituted Phenols to 2 H ‐Chromene Based Spiro ‐isoindolinones

We herein reported a formal [3+3] cyclization reaction between 3‐alkynyl‐3‐hydroxyisoindolinones and substituted phenols, which offered an efficient procedure for the preparation of 2 H ‐chromene‐based spiro ‐isoindolinones. 10 mol% of inexpensive catalyst (Cu(ClO 4 ) 2 ·6H 2 O or Fe(OTf) 3 ) proved to be the best to promote the tandem regioselective 1,4‐addition of phenols to the in situ generated β , γ ‐alkynyl‐ α ‐ketimine/intramolecular O ‐Michael addition to afford the desired products under mild conditions (25°C, 0.5–24 h) with a broad substrate scope (31 examples) in up to 99% yield. The synthetic utility was demonstrated by the scaled synthesis and further elaboration of the obtained products to polycyclic compounds bearing isoindolinone, 2 H ‐chromene and five or six‐membered O ‐heterocycles.