Cobalt-Catalyzed Enantioselective Directed C–H Alkylation of Indole with Styrenes

Abstract

A cobalt-chiral phosphoramidite catalyst promotes enantioselective imine-directed C2-alkylation of Boc-protected indoles with styrenes. The reaction affords 1,1-diarylethane products in moderate to good yields with good enantioselectivities under mild conditions. A deuterium-labeling experiment suggests that the enantioselectivity is controlled by both the styrene insertion and the C-C reductive elimination steps.

Jenseits von Friedel und Crafts: dirigierte Alkylierung von C‐H‐Bindungen in Arenen

“…[57] was den Produkten entspricht, die auch mit einem NHC-Ligand erhalten werden kçnnen. [55] Diese Methode wurde ausgeweitet auf die verzweigt-selektive ortho-Alkylierung aromatischer Aldimine [58] sowie auf die enantioselektive Alkylierung von 3-Iminoindolen mit Styrolen, [59] die auch in Kombination mit einer Isomerisierung ausgehend von nicht-konjugierten Alkenen [60] oder (nicht enantioselektiv) mit einfachen Eisenkatalysatoren ausgeführt werden kann. [61] Interessanterweise erwiesen sich N-H-Imine ebenfalls als effiziente Substrate fürd ie dirigierte Alkylierung mit Alke-nen, [62] und die Gruppe von Yoshikai berichtete 2016, dass sich die in all diesen Verfahren erforderlichen Grignard-Reagentien effizient durch einfaches Magnesiummetall ersetzen ließen.…”

Hydroarylations by cobalt-catalyzed C–H activation

“…Indoles also efficiently participated in intra- and intermolecular hydroarylation reactions to access useful organic skeletons [70–73]. Thus, the reaction of indole bearing an aldimine and homoallyl group 29 in the presence of CoBr 2 , SIMes·HCl and Me 3 SiCH 2 MgCl gave dihydropyrroloindoles 30 , whereas the IPr·HCl ligand provided tetrahydropyridoindoles 31 in reasonable regioselectivity (Scheme 22) [70].…”

“…In 2015, an asymmetric hydroarylation of styrenes with indoles was reported by Yoshikai and co-workers (Scheme 23) [73]. Among varies N -protected indoles, N -Boc indoles 32 in the presence of Co(acac) 3 and phosphoramidite ligand L afforded alkylated products 33 in high yields and enantioselectivity.…”

Iridium(I)‐Catalyzed Intramolecular Hydrocarbonation of Alkenes: Efficient Access to Cyclic Systems Bearing Quaternary Stereocenters

“…[19] This scarcity is even more evident in the case of hydroalkenylation processes,since only one example based on aRh I catalyst has been so far reported, and is limited to the generation of cyclic systems bearing tertiary stereocenters (up to 82 % ee). [19] This scarcity is even more evident in the case of hydroalkenylation processes,since only one example based on aRh I catalyst has been so far reported, and is limited to the generation of cyclic systems bearing tertiary stereocenters (up to 82 % ee).…”