Rh(iii)-Catalyzed [5 + 1] annulation of 2-alkenylanilides and 2-alkenylphenols with allenyl acetates

Abstract

Herein, we report a mild and highly regioselective Rh(III)-catalyzed non-oxidative [5+1] vinylic C-H annulation of 2-alkenylanilides with allenyl acatetes, which has been elusive so far. The reaction proceeds via vinylic...

Recent Advances in Alkenyl sp2 C–H and C–F Bond Functionalizations: Scope, Mechanism, and Applications

“…131 Quite recently, Volla et al established a nonoxidative protocol for the [5 + 1] annulation reaction of 2alkenylanilides (Scheme 57). 132 The reaction occurred smoothly at room temperature with allenyl acetates under Cp*Rh(III) catalysis, thereafter affording a number of highly functionalized 1,2-dihydroquinolines in excellent yields (76− 91%). On the basis of mechanistic studies, the authors tentatively proposed a catalytic cycle involving highly regioselective 2,3-migratory insertion, facile β-oxygen elimination, followed by intramolecular nucleophilic cyclization to elucidate the plausible pathway.…”

Merging C–H Bond Activation, Alkyne Insertion, and Rearrangements by Rh(III)-Catalysis: Oxindole Synthesis from Nitroarenes and Alkynes

“…Therefore, their formations, manipulations, and diversifications represent a significant stake for chemical companies, and the discovery of novel synthetic approaches fulfilling modern reaction ideals of green chemistry is still an important challenge, especially starting from low-functionalized materials. Since the pioneer studies by Fagnou on the Rh­(III)-catalyzed C–H bond annulation of acetanilides with alkynes for the synthesis of indoles, several N -directed C–H bond annulation protocols have been developed for straightforward access to N -heterocycles . However, the conditions often required a stochiometric amount of the oxidant.…”

Pd(ii)-catalyzed β- and γ-C-(sp3)–H dienylation with allenyl acetates

“…10,11 The selective functionalization of one of the double bonds of allenes based on the reaction conditions resulted in a variety of reaction outcomes like annulation, alkenylation and allylation. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] On the other hand, the low reactivity and non-polar character of aliphatic C(sp 3 )-H bonds along with the formation of conformationally feeble complexes post C-H activation make C(sp 3 )-H functionalization quite challenging (Scheme 1a, right). [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] Consequently it is not surprising that the coupling of distal aliphatic C(sp 3 )-H bonds with allenes remains unreported and hence is an unanswered problem.…”

“…10,11 The selective functionalization of one of the double bonds of allenes based on the reaction conditions resulted in a variety of reaction outcomes like annulation, alkenylation and allylation. 12–29…”