Asymmetric synthesis of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates

This study describes general methods for the enantioselective syntheses of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates through dirhodium tetracarboxylate-catalysed asymmetric cyclopropanation of vinyl heterocycles with aryl- or heteroaryldiazoacetates. The reactions are highly diastereoselective and high asymmetric induction could be achieved using either (R)-pantolactone as a chiral auxiliary or chiral dirhodium tetracarboxylate catalysts. For meta- or para-substituted aryl- or heteroaryldiazoacetates the optimum catalyst was Rh-2(R-p-Ph-TPCP)(4). In the case of ortho-substituted aryl- or heteroaryldiazoacetates, the optimum catalyst was Rh-2(R-TPPTTL)(4). For a highly enantioselective reaction with the ortho-substituted substrates, 2-chloropyridine was required as an additive in the presence of either 4 angstrom molecular sieves or 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Under the optimized conditions, the cyclopropanation could be conducted in the presence of a variety of heterocycles, such as pyridines, pyrazines, quinolines, indoles, oxadiazoles, thiophenes and pyrazoles.

Automated summary

The study presents general methods for the enantioselective syntheses of pharmaceutically relevant compounds through dirhodium tetracarboxylate-catalysed asymmetric cyclopropanation, achieving high diastereoselectivity and asymmetric induction. Under optimized conditions, the reactions can be conducted with various heterocycles to efficiently synthesize the desired compounds.