An Electrophilic Trifluoromethylthiolation of Silylenol Ethers and β‐Naphthols with Diethylaminosulfur Trifluoride and (Trifluoromethyl)trimethylsilane

Abstract

An efficient and general trifluoromethylthiolation of silylenol ethers and β‐naphthols have been accomplished employing the combination of diethylaminosulfur trifluoride (DAST) and (trifluoromethyl)trimethylsilane (CF3TMS) as source of electrophilic trifluoromethylthio moiety for the synthesis of α‐trifluoromethylthiolated carbonyl compounds and β‐naphthols in good yields. Important features of this method include wide functional group tolerance and use of readily available DAST/CF3TMS. Potential of the methodology was demonstrated via the synthesis of α‐trifluoromethylthiolated (+)‐4‐cholesten‐3‐one and naphthoquinone.magnified image

Diethylaminosulfur Trifluoride: A Novel, Low-Cost, Stable Double Thiolation Reagent for Imidazo[1,2-α]pyridines

“…Based on these preliminary mechanistic studies and relevant reports, − we proposed a reaction mechanism, as depicted in Scheme . Initially, 2-arylimidazo­[1,2-α]­pyridines ( 1a ) could exist as the resonance structure A , which reacts with DAST to furnish intermediate B with the elimination of HF.…”

“…First, the reaction of 2-arylimidazo­[1,2-α]­pyridines ( 1a ) with DAST ( 2a ) under the standard conditions in the presence of a radical scavenger (such as TEMPO or BHT) proceed well to form 3a in 75 and 77% yields, indicating that the reaction does not proceed through a radical mechanism (Scheme a). Next, given the possibility that DAST might be converted to the DAST difluorosulfinium salt derivative prior to reacting with 2-arylimidazo­[1,2-α]­pyridines ( 1a ) in the reaction, , we subject XtalFluor-E ( 5 ) to test the reaction under the standard conditions; nonetheless, a trace amount of the desired product was detected (Scheme b). Thus, the particular DAST difluorosulfinium salt derivative might not be formed in this transformation.…”

Transition-Metal-Free Synthesis of Aryl Trifluoromethyl Thioethers through Indirect Trifluoromethylthiolation of Sodium Arylsulfinate with TMSCF3

“…Trifluoromethyltrimethylsilane (TMSCF 3 ), Ruppert–Prakash reagent, is most widely used as a trifluoromethyl nucleophile due to its commercial availability, bench stability, and operational convenience. The combination of TMSCF 3 with sulfur compounds, such as S 8 , CuSCN/NaSCN, Na 2 S 2 O 3 , and DTSA, has been also employed to introduce the -SCF 3 group into aromatic substrates. The reactions proceeded smoothly to generate the desired products with broad functional group tolerance, but these methods were still restricted by the starting substrates, transition-metal-catalyzed reagent, and/or toxic byproducts.…”

Triphosgene/Sodium Organosulfinate System: A General and Efficient Electrophilic Thiolation of Silylenol Ethers and Electron-Rich Heteroaromatics

“…7 In 2018, Saravanan and Anbarasan developed an efficient and creative approach to electrophilic trifluoromethylthiolation, in which a combination of (diethylamino)sulfur trifluoride (DAST) and (trifluoromethyl)trimethylsilane (F 3 CTMS) were used as the source of CF 3 S groups to give -trifluoromethylthiolated carbonyl compounds (Scheme 1b). 8 However those methods are limited by the nature of the CF 3 S source, which are difficult to prepare, and by the high cost of the substrates. Thus, the use of more readily available or more easily handled sources of the CF 3 S group to promote the trifluoromethylthiolation of silyl enol ethers is highly desirable.…”