Amide-Directed Intramolecular Co(III)-Catalyzed C–H Hydroarylation of Alkenes for the Synthesis of Dihydrobenzofurans with a Quaternary Center

Abstract

The first example of Cp*Co­(III)-catalyzed intramolecular hydroarylation of allyl aryl ethers using an amide directing group for the preparation of 3,3-disubstituted dihydrobenzofurans in high yields is described. The reaction of the unactivated alkene is completely selective for the formation of the quaternary center, allowing different substitution patterns on the aromatic ring and the alkene. The cyclization can also be extended to the formation of six-membered rings and to N-homoallylindoles.

Cp*Co(III)-Catalyzed C–H Hydroarylation of Alkynes and Alkenes and Beyond: A Versatile Synthetic Tool

“…To the best of our knowledge, only two examples have been reported involving the use of alkynes (Scheme and ), while no examples regarding the use of olefins as coupling partners had been reported until recently. In fact, our group has reported the first Cp*Co­(III)-catalyzed intramolecular hydroarylation reaction of a variety of allyl phenyl ethers 81 for the efficient synthesis of benzofurans 82 , using an amide-directing group (Scheme a) . This reaction could also be extended to homoallyl phenyl ethers 83 to access different chromanes 84 (Scheme b).…”

“…In fact, our group has reported the first Cp*Co(III)-catalyzed intramolecular hydroarylation reaction of a variety of allyl phenyl ethers 81 for the efficient synthesis of benzofurans 82 , using an amide-directing group ( Scheme 31 a). 52 This reaction could also be extended to homoallyl phenyl ethers 83 to access different chromanes 84 ( Scheme 31 b). The use of the indole scaffold 85 as the arene coupling partner was also tolerated, obtaining dihydropyrrolo[1,2- a ]indoles 86 ( Scheme 31 c).…”

Transition-metal-catalyzed C–H bond alkylation using olefins: recent advances and mechanistic aspects

“…In 2020, Sotomayor, Lete and co-workers reported the first example of amide directed Cp*Co(III) catalyzed intramolecular hydroarylation of allyl aryl ethers 55a to afford 3,3-disubstituted dihydrobenzofurans 55b (Scheme 55). 125 This reaction well tolerated a wide range of substrates, including electronwithdrawing and electron-donating substituents on the arene ring, with good yields. Notably, AgSbF 6 had a significant role in achieving a better yield in the transformation.…”

Weak-Coordination in C–H Bond Functionalizations Catalyzed by 3d Metals

“…Identical to alkynes, alkenes can also be considered as effective π-coupling partners and Inspired by these earlier works, Lete and co-workers established an amide-directed Cp*Co(III)-catalyzed intramolecular hydroarylation of unactivated olefins to deliver 3,3disubstituted dihydrobenzofurans in good yields (Scheme 26). 103 Notably, the tertiary amide (e.g., N,N-dimethylbenzamide derivative) failed to direct the intramolecular hydroarylation process.…”