Convenient Synthesis of Dihydrobenzofuran‐Fused Spirocyclopentane‐1,2‐Diindolinone Scaffolds

The diverse functionalized dihydrobenzofuran‐fused spirocyclopentane‐1,2‐diindolin‐one scaffolds were conveniently synthesized by base promoted domino cyclization reaction of MBH (Morita‐Baylis‐Hillmann) carbonates of isatins and 3‐(o‐hydroxybenzylidene)indolin‐2‐ones. The base promoted reactions of MBH maleimides of isatins and MBH formates of isatins with 3‐(o‐hydroxybenzylidene)indolin‐2‐ones afforded polycyclic dispiro[indoline‐3,4′‐benzofuro[2′,3′:1,5]cyclopenta[1,2‐c]pyrrole‐5′,3′′‐indolines] and dispiro[indoline‐3,1′‐cyclopenta[b]benzofuran‐2′,3′′‐indolines] in good yields and with high diastereoselectivity. More importantly, DMAP facilitated annulation reaction of MBH nitriles of isatins and 3‐(o‐hydroxybenzylidene)indolin‐2‐ones selectively resulted in dispiro[indoline‐3,1′‐cyclopentane‐2′,3′′‐indolines], while Cs2CO3 promoted reaction gave dispiro[indoline‐3,1′‐cyclopenta[b]benzofuran‐2′,3′′‐indolines] in high yields and with high diastereoselectivity. The relative configurations of the various polycyclic compounds were clearly elucidated by determination several single crystal structures. A convenient synthetic protocol for diverse functionalized dihydrobenzofuran‐fused spirocyclopentane‐1,2‐diindolin‐ones with high diastereoselectivity is developed by base promoted domino annulation reaction of MBH carbonates of isatins and 3‐(o‐hydroxybenzylidene)indolin‐2‐ones. The relative configurations of the various polycyclic compounds are clearly elucidated by determination eight single crystal structures.