Catalyst-Controlled [3 + 2] and [4 + 2] Annulations of Oximes with Propargyl Alcohols: Divergent Access to Indenamines and Isoquinolines

Abstract

Rhodium(III)- and iridium(III)-catalyzed C-H activation of oximes and coupling with propargyl alcohols is discussed. Depending on the catalyst, the reaction pathway switched between [3 + 2] and [4 + 2] annulations, thus giving divergent access to indenamines and isoquinolines in a one-pot and atom-economical manner. The hydroxyl group in the tertiary propargyl alcohol substrate was found to be crucial in controlling chemoselectivity. Five-membered rhodacycle and iridacycle intermediates have also been identified for mechanism hypotheses.

Propargylic Alcohols as Coupling Partners in Transition‐Metal‐Catalyzed Arene C−H Activation

“…Based on mechanistic studies, a catalytic cycle was proposed, which started after the pyridyl assisted CÀ H activation (via a concerted metalation/deprotonation) In 2018, Yi and group [17] reported the Rh(III) and Ir (III) catalysts controlled regioselective CÀ H activation followed by [3 + 2] and [4 + 2] annulations of oxime with propargyl alcohol. The authors envisaged that the differences of various [Cp*TM(III)] in terms of Lewis acidity, steric effects, and coordination of tertiary propargyl alcohol may lead to a switch between [3 + 2] and [4 + 2] annulations at room temperature (Scheme 13).…”

Comparison of the Reactivities and Selectivities of Group 9 [Cp*MIII] Catalysts in C−H Functionalization Reactions

“…[19] The reaction of oximes with propargyl alcohols afforded indenamines by using [(Cp*RhCl 2 ) 2 ]( 10 mol %) and as toichiometric amount of silver acetate, whereas isoquinolines were obtainedb ys imply switchingt he catalystt o[ (Cp*IrCl 2 ) 2 ]. [19] The reaction of oximes with propargyl alcohols afforded indenamines by using [(Cp*RhCl 2 ) 2 ]( 10 mol %) and as toichiometric amount of silver acetate, whereas isoquinolines were obtainedb ys imply switchingt he catalystt o[ (Cp*IrCl 2 ) 2 ].…”

“…An elegant example of pathway-switching by the judicious choice of catalysts ystem between rhodium and iridium was reported by Yi and co-workers (Scheme 10). [19] The reaction of oximes with propargyl alcohols afforded indenamines by using [(Cp*RhCl 2 ) 2 ]( 10 mol %) and as toichiometric amount of silver acetate, whereas isoquinolines were obtainedb ys imply switchingt he catalystt o[ (Cp*IrCl 2 ) 2 ]. Both CÀHa nnulation reactions were performed at room temperature with highc hemoselectivity.T he authors attributed this switching to differences in the Lewis acidityo ft he catalyst, in addition to steric influences, to reason that the resultant RhÀCb ond in the vinyl rhodiumi ntermediate was more polarized than that in the iridium species.…”

“…An elegant example of pathway‐switching by the judicious choice of catalyst system between rhodium and iridium was reported by Yi and co‐workers (Scheme ) . The reaction of oximes with propargyl alcohols afforded indenamines by using [(Cp*RhCl 2 ) 2 ] (10 mol %) and a stoichiometric amount of silver acetate, whereas isoquinolines were obtained by simply switching the catalyst to [(Cp*IrCl 2 ) 2 ].…”

Highly Efficient Construction of Pentacyclic Carboline‐Containing Salts via a [Cp*RhCl2]2‐Catalyzed Tandem Reaction

“…[9] Among these distinct advances, tandem reactions of aromatic imines or unsaturated imines with alkynes attracted our attention. [12] Then the nitrogen atom in the newly generated pyridine ring, as the potential directing group, would initiate the second CÀ H activation and insertion of alkynes to afford pentacyclic carboline-containing salts (Scheme 2b). [10] Inspired by these results, we considered that CÀ H bond at C-2 or C-3 position of the indole ring might be activated by using imines as directing groups.…”