Co(III)‐Catalyzed [4+1] Annulation of Amides with Allenes via C−H Activation

Abstract

A Co(III)-catalyzed [4 + 1] annulation of amides with allenes to synthesize isoindolone and 1,5-dihydro-pyrrol-2-one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide-directed CÀH activation, followed by carbocobaltation of allene, b-hydride elimination, and an intramolecular 1,2hydroamination.

(3S,4S)‐N‐substituted‐3,4‐dihydroxypyrrolidines as ligands for the enantioselective Henry reaction

“…The use of polar and apolar solvents is mentioned in the literature, although polar protic solvents such as alcohols usually give better conversions and er . [ 43–46 ] Therefore, several alcohols were tested as solvents for the reaction and conversions higher than 96% were obtained in all cases. However, low er resulted with all the alcohols tested.…”

Asymmetric Alkenyl C−H Functionalization by CpxRhIII forms 2H‐Pyrrol‐2‐ones through [4+1]‐Annulation of Acryl Amides and Allenes

“…Notably, allenes with no preference for stabilization of the product double bond by conjugation perform equally well. Aliphatic allenes, which are considered challenging substrates in Cp*M‐catalyzed annulations, coupled smoothly. For instance, the reaction tolerates a wide range functional groups such as ester ( 3 aj , 3 an ), nitrile ( 3 ak ), hydroxy ( 3 al ), and ether ( 3 am ) functionalities, providing lactams 3 with a similar range of yields and enantioselectivity.…”

Metallaphotoredox-catalyzed C–H activation: regio-selective annulation of allenes with benzamide

“…Various noble second-and third-row transition metals such as Pd [26][27][28][29][30][31][32], Ir [33], Rh [34][35][36][37][38][39][40] and Ru [41], have been employed for the preparation of cyclic scaffolds from simple, nonfunctionalized acyclic starting materials. Moreover, the rst-row transition metals, such as Mn [42][43][44][45][46][47], Fe [48], Ni [49][50][51][52][53] and Co [54][55][56][57][58][59][60][61][62][63], have been recognized as cheap, environmentally friendly and reactively effective catalysis for C − H functionalization with allenes. Particularly, cobalt-catalyzed regioselective intermolecular cyclization reactions of arylamides or alkenylamides with allenes were independently reported by the group of Cheng [56][57][58], Volla [59], Rao [60], Zhai [61], and Ackermann [62]…”

“…Moreover, the rst-row transition metals, such as Mn [42][43][44][45][46][47], Fe [48], Ni [49][50][51][52][53] and Co [54][55][56][57][58][59][60][61][62][63], have been recognized as cheap, environmentally friendly and reactively effective catalysis for C − H functionalization with allenes. Particularly, cobalt-catalyzed regioselective intermolecular cyclization reactions of arylamides or alkenylamides with allenes were independently reported by the group of Cheng [56][57][58], Volla [59], Rao [60], Zhai [61], and Ackermann [62][63], which provide rapid synthetic routes for diverse isoquinolin scaffolds (Scheme 1a). Generally, stoichiometric amounts of metal oxidants (Ag 2 CO 3 , Mn(OAc) 2 , Mn(OAc) 3 , etc.…”