Rh(i)-catalyzed decarbonylative direct C2-olefination of indoles with vinyl carboxylic acids

Abstract

A general and efficient Rh(I)-catalyzed decarbonylative direct C2-olefination of indoles with vinyl carboxylic acids has been developed. The reaction exhibits excellent functional group tolerance, regioselectivity and stereoselectivity, giving a broad range of C2-alkenylated indoles in good to excellent yields.

Regioselective Direct C‐Alkenylation of Indoles

“…[53] Substituted acrylic acids can be employed as alkenylating reagents with N-(2-pyrimidyl)i ndoles in the presence of aR h I complex in ap rocess entailing ac oncomitantd ecarboxylation reaction( Scheme 16). [54] The procedure is highly efficient with an otable number of acrylic acids including di-a nd trisubstituted ones and also shows ah igh degree of E stereoselectivity in the obtained products. Interestingly,s ubstrates bearing as ubstitutiona tC -2 undergo to an alkenylation at C-7, evidencing the strong directing effect exertedb yt he 2-pyrimidyl group.…”

“…Substituted acrylic acids can be employed as alkenylating reagents with N‐( 2‐pyrimidyl) indoles in the presence of a Rh I complex in a process entailing a concomitant decarboxylation reaction (Scheme ) . The procedure is highly efficient with a notable number of acrylic acids including di‐ and trisubstituted ones and also shows a high degree of E stereoselectivity in the obtained products.…”

Transition Metal‐Catalyzed CH Activation of Indoles

“…[59] Thed esired 2-alkenylindoles were obtained in mostly good yields.R u catalysis can also be exploited for the coupling of indoles and olefins to prepare 2-alkenylindoles [60] and vinylcarboxylic acids have been useda sc oupling partners to prepare 2-alkenylindoles. [61] Allylationw as also recently achieved at the C-2p osition of indoles,e xploiting pyrimidinea uxiliaries to direct the C À Ha ctivation. [62] …”

“…Reaction Coupling partner/reagent Catalyst References 1a rylation aryl halides Rh [25] 2P d [26,27,[31][32][33] 3a renes Pd [28][29][30] 4d iaryliodoniumsalts Pd [33,35] 5a rylboronr eagents Pd [36][37][38] 6R h, Ru [39,40] 7a rylsilanes Rh [41] 8P d [42] 9b enzoic acid Rh [43] 10 alkynylationa lkynes Pd [44] 11 alkenylationP d [46,[50][51][52]54,55] 12 alkenes Rh [48,53,59] 13 Ru [53b,60] 14 vinylcarboxylic acids Rh [61] 15 Ru [49] 16 alkynes Fe [56] 17 Co [58] 18 alkylation alkyl halides Pd [63,65] 19 Co [66] 20 Pd [70] 21 Fe [56] 22 alkenes Ir [67,71] 23 Co [69] 24 Ir [72] 25 acylationa ldehydes Pd [75] 26 Rh [76] 27 annulations Co [57] 28 Pd [77,…”

Synthesis of Terminal Vinylindoles via RhIII‐Catalyzed Direct C−H Alkenylation with Potassium Vinyltrifluoroborate

“…[13] Recently,s elective fluoroalkenylation of N-pyrimidyl indoles with readily available gem-difluorostyrenes under mild conditions have been reported by Feng [14] and Li, [15] respectively.X ua nd Zhang disclosed an efficient Rh III -catalyzed direct ortho-olefination of indoles with unactivated aliphatic olefins. [13] Recently,s elective fluoroalkenylation of N-pyrimidyl indoles with readily available gem-difluorostyrenes under mild conditions have been reported by Feng [14] and Li, [15] respectively.X ua nd Zhang disclosed an efficient Rh III -catalyzed direct ortho-olefination of indoles with unactivated aliphatic olefins.…”