Convenient Synthetic Protocols for Diverse Functionalized Dihydrobenzofuran-Fused Spiro-indanedione-oxindole Scaffolds
Jing Sun, Xueyan Liu, Qiu Sun, Ying Han, Chao‐Guo Yan
Abstract
Diverse functionalized dihydrobenzofuran spiro-indanedione-oxindole scaffolds were conveniently synthesized by base-promoted cyclization reaction of Morita–Baylis–Hillman (MBH) carbonates of isatins and 2-( o -hydroxybenzylidene)-1,3-indanediones. The two diastereomeric dispiro[indene-2,1′-cyclopenta[ b ]benzofuran-2′,3″’-indolines] could be selectively synthesized by using DABCO or DMAP as a base promoter. More importantly, DABCO or DMAP facilitated the annulation reaction of MBH formates of isatins and 2-( o -hydroxybenzylidene)-1,3-indanediones selectively, resulting in spiro[cyclopropa[ c ]chromene-1,2′-indene]-1′,3′-diones or dispiro[indene-2,1′-cyclopenta[ b ]benzofuran-2′,3″’-indolines]. Additionally, a similar reaction with MBH maleimides of isatins afforded dispiro[indene-2,5′-benzofuro[2′,3′:1,5]cyclopenta[1,2- c ]pyrrole-4′,3″’-indolines] in high yields and with high diastereoselectivity.