Sulfonyl Chlorides Mediated Alkynylation of Non-activated Alkenes via Distal Alkynyl Group Migration

Abstract

Radical-mediated difunctionalization of alkenes through the remote functional group migration (FGM) process paves an ingenious avenue for simultaneous cleavage and reconstruction of C-C bonds. Recently, our group has systematically disclosed the strategy of remote FGM for radical-mediated difunctionalization of unactivated alkenes. A portfolio of functional groups including cyano, heteroaryl, alkynyl, oximino, and carbonyl showcase the migratory aptitude, leading to new C-C bonds under radical conditions. Meanwhile, a series of other chemical bonds such as C-C, C-N, C-P, C-Si, and C-S are readily constructed in the reaction. Considering the synthetic utility and flexible transformation of alkynes, the radical alkynylation of unactivated alkenes via remote alkynyl migration we firstly reported provides an efficient approach for the incorporation of alkynes and has received considerable attention. On the other hand, fluorine-and sulfonyl-containing molecules play vital roles in organic and medicinal chemistry owing to their important chemical and physical characters. Therefore, the concomitant introduction of an alkynyl and a trifluoromethyl/sulfonyl group into one molecule is of great synthetic value. Herein we report a useful method for carbo-trifluoroalkylation/sulfonylation of unactivated olefins. The addition of extrinsic radical to alkene triggers the intramolecular FGM via a five-membered transition state along with a cascade of bond fission and formation. The typical procedure is as follows: a mixture of propargyl alcohol 1, sulfonyl chloride, fac-Ir(ppy) 3 , and base is loaded in a flame-dried reaction vial which is subjected to evacuation/flushing with nitrogen three times. Solvent is added to the mixture via syringe and the mixture is then stirred at 25 ℃ until the starting material is consumed monitored by TLC. The mixture is concentrated, and purified by flash column chromatography on silica gel (eluent: petroleum ether/ethyl acetate) to give the product.

Radical-Mediated Remote Functional Group Migration

“…The quantum yield (Φ = 0.94) experiment elucidated that a photocatalytic process was present in the main pathway for the transformation. The expensive Umemoto’s reagent could be replaced by cheaper CF 3 SO 2 Cl in the reaction, affording the same products in slightly lower yields . In addition to the trifluoromethylative alkynylation, similar di/monofluoroalkylative alkynylation of unactivated alkenes was also achieved under the mild photocatalytic conditions …”

“…The expensive Umemoto's reagent could be replaced by cheaper CF 3 SO 2 Cl in the reaction, affording the same products in slightly lower yields. 42 In addition to the trifluoromethylative alkynylation, similar di/monofluoroalkylative alkynylation of unactivated alkenes was also achieved under the mild photocatalytic conditions. 29 Soon after, Studer et al disclosed a transition metal free, electron catalysis promoted protocol for the radical perfluoroalkylalkynylation of unactivated alkenes via remote alkynyl migration.…”

Research Progress in C—S Bond Formation Reaction of Olefins with Organic Sulfur Reagents under Photocatalyst-Free and Non-Electrochemical Conditions

“…值得注意的是, 对于以上述起始原料实现烯烃的官 能团化, 使用光催化 [163][164][165][166] 或电化学 [167][168][169][170] 方法具有较 好的前景. 这是因为, 这些转化反应条件温和 [171][172]…”

Recent Progress in Sulfonylation via Radical Reaction with Sodium Sulfinates, Sulfinic Acids, Sulfonyl Chlorides or Sulfonyl Hydrazides

“…In 2019, visible light induced alkynylation of non-activated alkenes via distal alkynyl group migration was discovered by Zhu group. [87] fac-Ir(ppy) 3 was proved to be efficient catalyst in this reaction, which can convert sulfonyl chlorides to sulfonyl radical via oxidative quenching reaction (Scheme 73). In the same year, the same group also realized the visible-lightinduced carbosulfonylation of unactivated alkenes via remote heteroaryl and oximino migration.…”