Rhodium‐Catalyzed Direct Oxidative CH Acylation of 2‐Arylpyridines with Terminal Alkynes: A Synthesis of Pyrido[2,1‐a]isoindoles

Abstract

A synthesis of pyridoA C H T U N G T R E N N U N G [2,1-a]isoindoles is reported by the rhodium-catalyzed direct oxidative C À H acylation of 2-aryl pyridines with terminal alkynes. The desired products were obtained in moderate to excellent yields. This is an efficient and clean method to construct C

Rhodium‐Catalyzed Cascade Annulation Reaction via C−H Activation of Azobenzenes with Terminal Alkynes: A Synthesis of Indolo[1,2‐b]cinnolines

“…On the basis of preliminary mechanistic studies and our previous work,, a plausible mechanism is proposed (Scheme ). Rhodium (II) acetate dimer reacted with azobenzene to generate complex A .…”

“…Our initial effort focused on the reaction of azobenzene 1 a and phenylacetylene 2 a as model substrates catalyzed by rhodium (II) acetate dimer in N , N ‐dimethylformide (DMF) at 140 °C in the presence of Cu(OAc) 2 (4.0 equiv.) under argon atmosphere for 8 hours according to our previous work . The reaction afforded the product phenyl(11‐phenylindolo[1,2‐ b ]cinnolin‐12‐yl) metha‐none ( 3 aa ) in 61% yield (Table , entry 1).…”

“…Although o ‐xylene was not beneficial to the yield (42%), only the reactants and desired compound were existed in the reaction system. According to our previous work, the mixed solvents could optimize the reaction . Therefore, we chose mixed solvents with different ratios for the reaction, and found the mixture of o ‐xylene and DMF (1/1) improved the yield up to 95% (Table , entries 5, 8–12).…”

Development and Cycloaddition Reactivity of a New Class of Pyridine‐Based Mesoionic 1,3‐Dipole

“…[11,16] Typical synthetic approaches to these products include cyclizations with synthetic pyridine or pyrrole derivatives, [17][18][19] substitution on preformed indolizines, [20] or 1,3-dipolar cycloaddition with pyridinium ylides. [11,16] Typical synthetic approaches to these products include cyclizations with synthetic pyridine or pyrrole derivatives, [17][18][19] substitution on preformed indolizines, [20] or 1,3-dipolar cycloaddition with pyridinium ylides.…”

Development and Cycloaddition Reactivity of a New Class of Pyridine‐Based Mesoionic 1,3‐Dipole

“…Indolizines are present in ar ange of pharmaceutically relevant products as well as electronic materials. [11,16] Typical synthetic approaches to these products include cyclizations with synthetic pyridine or pyrrole derivatives, [17][18][19] substitution on preformed indolizines, [20] or 1,3-dipolar cycloaddition with pyridinium ylides. [21] 2 can be considered as tabilized, mesoionic analogue to these latter 1,3-dipoles,and offers the ability to incorporate ar ange of aryl, heteroaryl and alkyl units into the 3-indolizine position from simple imines.Asan illustration of the utility of this approach, ester-substituted indolizines such as 5 (Scheme 3) has been shown by Lan and Yout ob es trong blue emitting materials of use in fluorescence imaging.…”