- Copper-Catalyzed Coupling Reactions of Cyclobutanone Oxime Esters with Sulfur Nucleophiles at Room Temperature
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A copper-catalyzed iminyl radical-mediated C-C bond cleavage/cross-coupling tandem reaction of cyclobutanone oxime esters with aryl thiols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at room temperature was developed, and aryl cyanopropyl sulfides were smoothly synthesized in 20-88% yields. By altering the copper reagent and the molar ratio of cyclobutanone oxime ester/aryl thiol/DBU, substitutional product N-arylthio cyclobutanone imines were selectively generated in 50-91% yields. Using this protocol, C-S bond and N-S bond formations using aryl thiols as sulfur sources were realized under very mild conditions without the use of photocatalysis and electrocatalysis techniques.
- He, Mingchuang,Yan, Zhaohua,Zhu, Fuyuan,Lin, Sen
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p. 15438 - 15448
(2019/01/04)
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- N-Sulfonylcarboxamide as an Oxidizing Directing Group for Ruthenium-Catalyzed C–H Activation/Annulation
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N-Sulfonylcarboxamides can act as both a directing group for C–H activation and an internal oxidant in the Ru-catalyzed annulation reaction with alkynes to give isoquinolones. Of all of the N-sulfonylcarboxamides that were studied, the N-(2,6-difluorophenyl)sulfonamide derivatives were found to be the most efficient and led to the formation of an unstable sulfinate byproduct that decomposed into 1,3-difluorobenzene under the reaction conditions. The described isoquinolone synthesis provides an alternative to the currently known traceless annulations of hydroxamic acid and sulfoximine derivatives.
- Petrova, Elina,Rasina, Dace,Jirgensons, Aigars
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p. 1773 - 1779
(2017/04/13)
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- Hydroxylamine as an oxygen nucleophile: Substitution of sulfonamide by a hydroxyl group in benzothiazole-2-sulfonamides
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Benzothiazole-2-sulfonamides react with an excess of hydroxylamine in aqueous solutions to form 2-hydroxybenzothiazole, sulfur dioxide, and the corresponding amine. Mechanistic studies that employ a combination of structure-reactivity relationships, oxygen labeling experiments, and (in)direct detection of intermediates and products reveal that the reaction proceeds via oxygen attack, and that oxygen incorporated in the 2-hydroxybenzothiazole product derives from hydroxylamine. The reaction, which is performed under mild conditions, can be used as a deprotection method for cleavage of benzothiazole-2-sulfonyl-protected amino acids.
- Kamps, Jos J. A. G.,Belle, Roman,Mecinovi?, Jasmin
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supporting information
p. 1103 - 1108
(2013/03/28)
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- A total synthesis of (-)-hemiasterlin using N-Bts methodology
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A total synthesis of (-)-hemiasterlin has been accomplished in nine steps from 258 (>35% yield overall). An improved enantiocontrolled route to the tetramethyltryptophan subunit 32 was developed using an asymmetric Strecker synthesis (five steps, 50% yield from 25), and the dipeptide 22 was prepared in seven steps, 37% yield from valinol. The synthesis exploits the high reactivity of a Bts-protected amino acid chloride in the difficult peptide coupling of sterically hindered amino acid residues 18 and 20 to form 21 (70%, recrystallized) and also uses N-Bts intermediates for the high-yielding N-methylations of 14 and 31. In addition, the Bts-protected di-tert-butyl N-acylimidodicarbonate 33 is shown to undergo efficient coupling with 22 to form 34 (97% in the coupling step; 79% over the activation; coupling sequence from 32).
- Vedejs,Kongkittingam
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p. 7355 - 7364
(2007/10/03)
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