Conjugated Diene-Assisted Allylic C−H Bond Activation: Cationic Rh(I)-Catalyzed Syntheses of Polysubstituted Tetrahydropyrroles, Tetrahydrofurans, and Cyclopentanes from Ene-2-Dienes

摘要

Selective C-H functionalization represents one of the mostnefficient and straightforward methods for accessing complexnmolecules from ubiquitous C-H groups.1 Among various C-Hnactivation/C-C bond-forming reactions, the addition of C-H bondsnacross multiple bonds such as alkenes and alkynes is particularlynappealing in light of atom- and step-economy considerations.2 Inncomparison with the addition of aromatic C-H bonds to multiplenbonds, the addition of aliphatic C-H bonds to multiple bonds isnmore challenging because of the inertness of aliphatic C-H bondsnand problems with site selectivity. Thus, many efforts have beenndirected to the activation of C-H bonds adjacent to heteroatomsnor double bonds.3 However, only limited examples of catalyticnadditions of allylic C-H bonds to alkynes and allenes have beennreported.4-6 In particular, catalytic addition of allylic C-H bondsnto alkenes has not been forthcoming.