Efficient and Facile Synthesis of Chiral Sulfonamides via Asymmetric Multicomponent Reactions

Sulfonamide is a key structural unit of several groups of vitally synthetic drugs that have been extensively used as antimicrobials, antiretroviral drugs and anticancer agents. In particular, enantiomerically pure sulfonamides represent a rapidly-increasing important substance in new drug discovery due to their unique pharmacological properties. Thus, developing asymmetric synthetic methods involving rapid and highly efficient construction of these compounds is extremely important and highly demanded for medicinal chemists. In our laboratory, we have reported a serial of asymmetric multicomponent reactions via trapping reactive ammonium ylides generated from amines and diazo compounds in the presence of transition metal complexes and chiral phosphoric acids. In this work, an asymmetric three-component reaction of sulfonamides, diazo compounds and imines cooperatively catalyzed by Rh-2(OAc)(4) and chiral phosphoric acids was reported. This Rh-2(OAc)(4) and chiral phosphoric acids cooperatively catalyzed three-component reaction of sulfonamides, diazo compounds and imines accomplished with satisfying yields (up to 85%), high diastereoselectivity (>20 : 1) and excellent enantioselectivity (up to 99% ee), thus providing a rapid access to synthesize enantiomerically enriched sulfonamides bearing two adjacent chiral carbons. Furthermore, this newly developed three-component reaction was carried out on a gram-scale with a lower catalyst loading and without impacting the yield, diastereoselectivity and enantioselectivity. Finally, we explored the further transformation of obtained three-component reaction products: 1) treatment of 5aaa with LiAlH4 under 0 degrees C in THE for 8.0 h gave the corresponding alcohol derivative 6 in 82% yield without changing the diastereoselectivity and enantioselectivity (0.20 mmol scale); 2) treatment of 5aaa with triphosgene and triethylamine under 0 degrees C in DCM for 1.0 h, gave five-membered heterocyclic sulfoximine derivative 7 bearing three adjacent chiral atoms (2 carbons and 1 sulfur) in 80% yield with perfect diastereoselectivity (>20 : 1) and remained enantioselectivity (0.20 mmol scale).