title: Unusual formal [4 + 2] cycloaddition of ethyl allenoate with arylidenoxindoles: synthesis of dihydropyran-fused indoles.
abstract: An unusual DABCO-catalyzed formal [4 + 2] cycloaddition of ethyl allenoate, as a surrogate of a "1,2-dipole", with various arylidenoxindoles has been developed for the synthesis of dihydropyran-fused indoles. The DFT mechanistic study indicates that the cycloaddition takes place stepwise and the essential role of the catalyst is to raise the HOMO of allenoate.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiang-Yu
authors.initials: XY
authors.lastname: Chen
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Wen
authors.forename: Song
authors.initials: S
authors.lastname: Ye
authors.forename: Zhi-Xiang
authors.initials: ZX
authors.lastname: Wang
mesh_terms: D002384:Catalysis; D003500:Cyclization; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D007211:Indoles; D011714:Pyrans