FeCl₃ mediated dimerization of dihydropyrrolo[2,1-a]isoquinolines and chlorination of tetrasubstituted pyrroles

Abstract

We have developed a mild FeCl3-mediated dimerization of dihydropyrrolo[2,1-a]isoquinolines through oxidative homocoupling (35–>99% yield) and chlorination of tetrasubstituted pyrroles (18–70% yield).

Iron Catalyzed [3+2] Cycloaddition of Tetrahydroisoquinoline: Synthesis of Dihydropyrrolo[2,1‐a]isoquinolines

“…In general, acceptable to moderate yields were obtained in most cases. Two possible reasons should account for the relatively low yields in this study: (1) Only moderate yield of SN2’ product can be formed in the reaction system, as amide group in the substrate may be involved in N‐allylic alkylation reaction; (2) Side reactions of desired products 4 , such as iron mediated/catalyzed dimerization and decomposition of products 4 via the formation of heteroarene cation radicals . Therefore, it is reasonable that compounds 4 would gradually diminish when heated at 150 °C for longer reaction time (monitored by TLC).…”

Modification of Pyrrolo[2,1-a]isoquinolines and Polysubstituted Pyrroles via Methylenation with Acetyl Chloride and Dimethylsulfoxide

“…Since methylthiomethylenation products have been reported as key intermediates by others and us for further transformations, − compound 10 was tested under the optimal conditions. The desired product 2a can be obtained in 67% yield, demonstrating that the methylthiomethylenation product may also be as a crucial intermediate in the current reaction system (eq 3 ).…”

“…It should be pointed out that it depends on the reaction conditions whether methylthiomethylenation product 10 could be converted to methylene-bridged pyrroloisoquinoline 2k . In our previous study, it was found that a NH 4 OAc/DMSO reaction system could be able to transform methylene-bridged product 2a to methylthiomethylenation product 10 irreversibly . In contrast, the methylthiomethylenation products were stable under the NH 4 OAc/DMSO system.…”

“…Later, we developed an efficient dicarbonylation reaction by employing aroyl bromide and DMSO to synthesize 1,2-dicarbonylated pyrroloisoquinolines . DMSO can act as a methylthiomethylating reagent for functionalizing pyrroloisoquinolines in the presence of ammonium acetate . In this reaction system, methylene-bridged pyrroloisoquinolines can be detected in low yields as minor products.…”

Advances in C(sp2)−H/C(sp2)−H Oxidative Coupling of (Hetero)arenes Using 3d Transition Metal Catalysts

“…serotonin and decursivine derivatives. Recently, Cui reported the iron‐mediated methodology for the homocoupling of dihydropyrrolo[2,1‐a]isoqhuinolines [82] . Iron complexes in the cross‐dehydrogenative coupling of other heteroarenes require significant investigation to achieve sustainability in the field.…”