Synthesis of Various α‐Substituted Alkenyl Sulfoxides from Alkynes and β‐Sulfinyl Esters

Abstract

Methods to synthesize α‐substituted alkenyl sulfoxides are highly useful as they are widely used to construct diverse molecules of high synthetic importance. We have described a synthetic route for expedient access to the numerous α‐substituted alkenyl sulfoxides from alkynes and β‐sulfinyl esters. This protocol exhibits a vast substrate scope, readily accommodates a wide range of functional groups, and is scalable in a gram‐scale. Besides, we demonstrated a direct synthesis of alkenyl sulfoxides from thiols via the in situ generation of the requisite β‐sulfinyl ester. The ensuing α‐substituted alkenyl sulfoxide product was readily transformed into benzofuran and sulfonyl derivatives. Mechanistic investigations were done to comprehend the reaction mechanism.

Redox transformation of β-sulfinyl esters for asymmetric synthesis of sulfone-based axially chiral styrenes

“…Besides, increasing the concentration resulted in a slight reduction of yield (Table 1, entry 17). Temperature was also investigated and 60 °C was better than others (Table 1, entries [18][19][20]. Therefore, the optimal conditions were confirmed as below for up to 88% yield and 97% ee: 1a : 2a = 1 : 5 with 10 mol% CuI and Cat-III in 1.0 mL of 2-MeTHF at 60 °C for 48 h (Table 1, entry 15).…”

“…In the presence of Cat-III and under heating conditions, 2a generates the quaternary ammonium salts of sulfenate anions, Int-A and Int-B, 13h and releases methyl acrylate through a retro-Michael process. 18,19 The corresponding copper sulfinate-based complex Int-C is formed in the presence of CuI and then undergoes the asymmetric addition towards the VQM intermediate, which is in situ generated from the o-alkynyl naphthol 1a. 4a Afterwards, the desired product 3aa is generated along with the release of a free catalyst.…”

Transition metal-free and regioselective alkenyl C–S cross-coupling reaction of alkenylsulfonium salts

“…In this regard, palladium-catalyzed cross-coupling reactions of in situ generated sulfenate anions with aryl/alkenyl iodides, allyl acetates and allenamides have been well developed by Poli, 12 Walsh, 13 Perrio 14 and other groups. 15 In addition, transition metal-free synthesis of sulfoxides from in situ generated sulfenate anions with alkyl halides, 16 diaryliodonium salts, 17 and alkynes 18 was also developed. Inspired by these results and as a result of our continuous interest in exploring the reactivity of sulfenate anions, we envision that the merging of the sulfenate anion with the alkenylsulfonium salt chemistry may result in new sparkles.…”

Heteroarylation of Sulfenate Ions In Situ Generated from β-Sulfinyl Esters under Transition-Metal-Free Conditions

“…Moreover, sulfur-based nucleophiles such as sulfinates (RSO 2 – ) and thiolates (RS – ) have been widely used for making C–S bonds in the presence/absence of a transition-metal catalyst . The sulfenate ion (RSO – ), an unstable, reactive species, has been recently employed as the sulfinylating agent for the synthesis of numerous sulfoxide derivatives. , …”

“…β-Sulfinyl esters have been widely explored as the source of sulfenate ions and sulfenic acids . The group of Perrio and Metzner demonstrated the synthesis of alkylated sulfoxides by intercepting the in situ formed sulfenate ions (from β-sulfinyl esters) with the reactive alkyl halides .…”