- Highly enantioselective transfer hydrogenation of racemic α-substituted β-keto sulfonamides: Via dynamic kinetic resolution
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Highly enantioselective transfer hydrogenation of β-keto sulfonamides was developed via dynamic kinetic resolution using a chiral Ru(ii) catalyst with an azeotropic solution of HCO2H/Et3N as a hydrogen donor, affording α-substituted β-hydroxyl sulfonamides in good yields with excellent diastereo- and enantioselectivities. This method is featured with mild conditions, easy operation, and a broad substrate scope, which make it possible to find wide applications in the synthesis of natural products and biologically active compounds containing the α-substituted β-hydroxyl sulfonamide core.
- Xiong, Zhichao,Pei, Chengfeng,Xue, Peng,Lv, Hui,Zhang, Xumu
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supporting information
p. 3883 - 3886
(2018/04/20)
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- Secondary Reactions of Sulfenes from Sulfonyl Chlorides and Tertiary Amines. 2. Formation of Episulfones, Sulfonylsulfene - Amine S,N-Adducts and Chlorsulfines from Primary Sulfonyl Chlorides and Tertiary Amines
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The reaction of primary sulfonyl chlorides 1b-m with the tertiary amine bases quinuclidine, DABCO, Me3N, Et3N, Bu3N, EtiPr2N, and 1,2,2,6,6-pentamethylpiperidine is studied in acetonitrile solution between -40 and 80 deg C.The 2,3-dialkylthiirane 1,1-dioxides 4 (trans/cis > 1) and the alkenes 5 1> are obtained in high yields with Et3N at -40 deg C.The stereochemistry is influenced by the amine base B in the ring-closure reaction and partially by epimerization of the episulfones 4.Hindered bases favor the cis, β-branched sulfonyl chlorides the trans isomer.Competing formation of the sulfonylsulfene - amine S,N-adducts 7 is only observed with quinuclidine, DABCO, and Me3N, which are also the most active amines in the epimerization of the cis-2,3-diarylthiirane 1,1-dioxides 4.Methanesulfonyl chloride (1a) yields the mesylsulfene - amine S,N-adducts 7a with Me3N and Et3N in MeCN, but thiirane 1,1-dioxide (4a) with EtiPr2N in MeCN or with Et3N in Et2O.Formation of chlorosulfines 10 is favored by higher temperature (T > 20 deg C), hindered amine bases and β-branched sulfonyl chlorides.Isolation of 10g and 10h in high yields shows that tert-alkylchlorosulfines are rather stable sulfines.
- Opitz, Guenter,Ehlis, Thomas,Rieth, Karlheinz
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p. 1989 - 1998
(2007/10/02)
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