Recent advances in sulfenylation of C(sp3) H bond under transition metal-free conditions

Review on Asymmetric Catalysis Employing 5H‐Oxazol‐4‐Ones as α‐Hydroxy Carboxylic Acid Surrogates

“…Among them, the asymmetric sulfa-Michael reaction was one of the most convenient and most explored reactions. [83][84][85][86] On the other hand, asymmetric sulfenylation reactions are relatively less explored where sulfur acts as an electrophile. [87][88][89] A novel asymmetric α-sulfenylation of 5H-oxazol-4-ones to N-(sulfenyl)succinimides 158 catalyzed by cinchona alkaloid-derived squaramide was successfully established in 2014, [90] to incorporate CÀ S bond at 5-position of oxalactims with excellent enantioselectivity (Scheme 56).…”

Mild and Expeditious Synthesis of Sulfenyl Enaminones of l-α-Amino Esters and Aryl/Alkyl Amines through NCS-Mediated Sulfenylation

“… 6 − 8 On the other hand, nowadays, chemists are more concern about environmental pollution; therefore, metal-free C–H functionalization is also receiving considerable attention. 9 In this context, cross-dehydrogenative coupling (CDC) is considered as an effective strategy for construction of C–C and C-heteroatom bonds as it provides an atom economical and environmentally benign short synthetic pathway without any prerequisite functionalization of reactants. 10 , 11 Since aliphatic/heteroaromatic sulfides, diaryl sulfides, and their derivatives are widely present in biologically active compounds and natural products, 12 chemists are fascinated in developing efficient methods to create a C–S bond specially using a CDC strategy.…”

“…Presently, C­(sp 2 )–H bond functionalization is considered as an essential transformation in organic synthesis, and a wide range of reactions such as C–H alkylation, alkenylation, arylation, and acylation mostly based on transition-metal catalysis and oxidative coupling have been reported. Similarly, C–S, C–P, and C–N bond formation via transition-metal-catalyzed C–H functionalization has become popular in recent years. − On the other hand, nowadays, chemists are more concern about environmental pollution; therefore, metal-free C–H functionalization is also receiving considerable attention . In this context, cross-dehydrogenative coupling (CDC) is considered as an effective strategy for construction of C–C and C-heteroatom bonds as it provides an atom economical and environmentally benign short synthetic pathway without any prerequisite functionalization of reactants. , Since aliphatic/heteroaromatic sulfides, diaryl sulfides, and their derivatives are widely present in biologically active compounds and natural products, chemists are fascinated in developing efficient methods to create a C–S bond specially using a CDC strategy.…”

Total Synthesis of (−)-Glionitrin A and B Enabled by an Asymmetric Oxidative Sulfenylation of Triketopiperazines

“…To this end, we considered the low basicity of triketopiperazine (TKP) enolates 25 as an entry to forge the first C–S bond by reaction with a suitable sulfur electrophile ( Figure 1 C). 26 This would give a chiral intermediate 8 from which glionitrin A and B could be pursued. An asymmetric oxidative sulfenylation of a TKP has, to our knowledge, not been reported, but a nonstereoselective sulfenylation of N , N -dimethyltriketopiperazine was recently shown by Snaddon, 27 and oxidation of TKPs was pioneered in ETP synthesis by Overman.…”

“…We thus concluded that an asymmetric solution to the glionitrin-problem was contingent on developing a mild and most likely stepwise approach to the DTDKP core. To this end, we considered the low basicity of triketopiperazine (TKP) enolates as an entry to forge the first C–S bond by reaction with a suitable sulfur electrophile (Figure C) . This would give a chiral intermediate 8 from which glionitrin A and B could be pursued.…”