Design and Synthesis of C₄‐Symmetric Axially Chiral β‐Aryl Porphyrins and Application for Supporting Ir(III)‐Catalyzed Enantioselective C−H Alkylation

Abstract

A hitherto unknown class of C4‐symmetric Caryl−Cβ (C3, C8, C13, C18) axially chiral porphyrins has been synthesized and the application of their iridium (Ir) complexes in catalytic asymmetric C(sp3)−H functionalization is documented. Cyclotetramerization of enantioenriched axially chiral 2‐hydroxymethyl‐3‐naphthyl pyrroles under mild acidic conditions affords, after oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ), the C4‐symmetric α,α,α,α‐atropenantiomer as an only isolable diastereomer. Both regioisomeric Ir(Por*)(CO)(Cl) complexes catalyze the carbene C−H insertion reaction affording the same enantiomer, albeit with slight difference in enantioselectivity. With the optimum Ir‐complex 3e, the 2‐substituted arylacetic acid derivatives were generated from diazo compounds and cyclohexadiene in excellent yields and enantioselectivities.