An Effective Method to Introduce Carbon Acid Functionality: 2,2‐Bis(trifluoromethanesulfonyl)ethylation Reaction of Arenes

Organic Acid Catalysts in Reactions of Lactones with Silicon Enolates

“…Keeping this idea in mind, we examined the catalysis of zwitterion 2 as a suitable acid. As mentioned in previous reports, the pK a value of triple carbon acid 1 a is 2.0 [9] and that of zwitterion 2 a, which is derived from N,N-dimethylaniline, is 2.4. [10] The same TLC analysis as above revealed that the conversion rate of the silyl acetal 4 a to the vinyl ether 5 aa is not so fast in the presence of a catalytic amount of 1 a.…”

“…This reaction did not proceed in the absence of any acidic additives and resulted in recovery of 3 a (Table 1, entry 1). On the other hand, when the reaction was conducted in the presence of some strong Brønsted acids, such as TfOH and Tf 2 NH, unusual olefination product 5 aa was obtained in very low yields ( Finally, we successfully found that triple carbon acid 1 a, which was developed by us, [9] has excellent catalytic activity for inducing this reaction. That is, in the presence of 1 a (2.0 mol %), the desired (Z)-vinyl ether 5 aa was isolated in 85 % yield with complete consumption of 3 a by using two equivalents of the KSA (Table 1, entries 7 and 8).…”

“…[8] As shown in Scheme 2, we found that carbon acid 1 can be easily prepared by the reaction of electronically rich arenes, such as phenols and aryl ethers, with Tf 2 C=CH 2 that is generated in situ from Tf 2 CHCH 2 CHTf 2 . [9] Moreover, zwitterKeywords: ketene silyl acetals · lactones · Mukaiyama aldol reaction · organocatalysis · zwitterions Abstract: By choosing the organic acid catalysts, the reaction of lactones with ketene silyl acetals results in selective formation of simple Mukaiyama aldol adducts or olefination products, which are formed by the subsequent elimination of a silanol from the adducts. That is, in the presence of acidic zwitterions, the reaction of lactones with ketene silyl acetals gives simple Mukaiyama aldol adducts in excellent yields.…”

Synthesis of superacidic carbon acid and its derivatives

“…Under optimized conditions using Tf 2 CHCH 2 CHTf 2 6 as a precursor of Tf 2 C=CH 2 24, it was successfully achieved to introduce the carbon acid functionality into several electronically rich arenes such as substituted phenols and aryl ethers (Figure 3) [58]. Interestingly, when the reaction carried out by using 2 or 3 equiv of 6 toward starting aromatics, unusual di-and tri-substitutions smoothly occurred to give the corresponding multiple carbon acids such as 48-50 in reasonable isolated yields.…”

Chemistry of Fluorinated Carbon Acids: Synthesis, Physicochemical Properties, and Catalysis

“…Selected data are summarized in Chart 29. In a series of phenol-derived carbon acids 15d, 16, and 17, the pK a values in DMSO solution were determined to be 2.3, 2.1, and 2.0, respectively, 39) using an electrochemical method. 51,52) Compared with the pK a values of Tf 2 CH 2 1 (2.1) and phenol (18) in DMSO solutions, 11) the values measured in our acids suggested that the major acidic functionality was the Tf 2 CH group rather than the phenolic hydroxyl group.…”