Nitrophenyl triflate, reactions

Phenolic triflates are formed with 4-nitrophenyl triflate in the presence of K2CO3 in DMF or with Triflic anhydride in the presence of an amine base. It can be cleaved with Et4NOH in dioxane or with TBAF in THF (70-99% yield). Et4NOH will also cleave phenolic mesylates and tosylates. These triflates are also substrates for a variety of Pd-catalyzed coupling reactions. 

Due to the importance of aryl triflates and related compounds in modern organic chemistry, including metal catalysed cross-coupling reactions, an efficient procedure for the triflation or nonaflation of phenols has been developed by the combination of PS-TBD (3 equiv.) and a perfluoroalkanesulfonyl transfer reagent (3 equiv.) such as p-nitrophenyl triflate or nonaflate [30] (Scheme 6.2). In this case, the free PS-TBD reagent could be recovered by washing successively with diluted acid, base, water and organic solvents, and almost comparable results were obtained with use of the recycled catalyst. 

It has been shown that, in the reactions of phenoxides with 4-nitrophenyl triflate (9) in DMF, nucleophilic attack occurs at the sulfur centre (path a) however, with 2,4-dinitrophenyl triflate, attack is switched to the carbon centre (path b). Oxydehalogena-tion reactions of l-halo-2-methylsulfonylbenzenes with amino alcohol nucleophiles have been used in the synthesis of thiotomoxetine, and reactions of 2-dialkylamino-1-ethoxides with 3-aroyl-2-arylbenzothiophenes have been used in the synthesis of raloxifene. Other reports involve the methoxydehalogenation reactions of 6-halo-1,2-acenaphthylene derivatives " and nucleophilic attack on a phenylacetic mustard. ... 

Aryl fluorosulfonates have recently been reported as less expensive alternatives to aryl triflates. Compound 3 has been synthesized in 50% isolated yield using 4-nitrophenyl fluorosulfonate as the electrophilic partner in the cross-coupling reaction. Roth, G. P. Fuller, C. E. J. Org. Cham. 1991,56,3493-3496. 

In 2010, Weinreb and coworkers reported their synthesis of communesin F (17) [30]. The synthesis began with known enol triflate 37. A Suzuki-Miyaura crosscoupling with 0-nitrophenyl boronic acid (38) followed by a two-step reaction with iodoaniline 39, afforded amide 40. A one-pot displacement of the benzyl group with ethyl carbamate, amide nitrogen protection, and a subsequent intramolecular Heck reaction provided enamide 41 (Scheme 5). 

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