An enantioselective one‐pot catalytic strategy to dihydroquinoxalinones, featuring novel 1‐phenylsulfonyl‐1‐cyano enantioenriched epoxides as masked α‐halo acyl halide synthons, followed by a domino ring‐opening cyclization (DROC), is documented. A popular quinine‐derived urea served as the catalyst in two out of the three steps performed in the same solvent using commercially available aldehydes, (phenylsulfonyl)acetonitrile, cumyl hydroperoxide and 1,2‐phenylendiamines. Medicinally relevant 3‐aryl/alkyl‐substituted heterocycles are isolated in generally good to high overall yield and high enantioselectivity (up to 99 % ee). A rare example of excellent reusability of an organocatalyst at higher scale, subjected to oxidative conditions, is demonstrated. Mechanistically, labile α‐ketosulfone has been detected as the intermediate involved in the DROC process. Theoretical calculations on the key epoxidation step rationalize the observed stereocontrol, highlighting the important role played by the sulfone group.

A one-pot enantioselective route to N-unprotected 2,3-dihydro-1,5-benzothiazepinones, by an organocatalyzed sulfa-Michael reaction of readily available α,β-unsaturated N-acyl pyrazoles with 2-aminothiophenols followed by silica-gel-catalyzed lactamization, has been developed. The method proceeds under mild conditions at room temperature and it requires only 1 mol % catalyst loading, to give 2-aryl/alkyl-substituted 1,5-benzothiazepines in generally good to excellent yields and enantioselectivities. The process, used for a short synthesis of antidepressant drug (R)-(-)-thiazesim, represents the first method to access enantioenriched unprotected 1,5-benzothiazepines, which are useful for rapid derivatization in drug discovery.

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SummaryAn investigation on the stereoselective cascade sulfa-Michael/aldol reaction of nitroalkenes and commercially available 1,4-dithiane-2,5-diol to 3,4,5-substituted tetrahydrothiophenes, bearing a quaternary stereocenter, is presented. A secondary amine thiourea derived from (R,R)-1,2-diphenylethylamine was found to be the most effective catalyst when using trans-β-methyl-β-nitrostyrenes affording the heterocyclic products in good yields and moderate stereoselectivities.

A practical and mild approach to prepare tetrahydropyrazolo[1,2-a]-pyrazole-1,7-diones, bearing up to three stereocentres, by reacting ready available N,N'-cyclic azomethine imines and pyrazoleamides under catalytic loading of commercial 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), has been developed. The products are obtained in good yields and high diastereoselectivity, working at room temperature. Preliminary bioassay showed the products to inhibit growth of Gram-positive bacteria.