Ethyl triflate

Ethyl triflate and benzyl triflate react with the cubane at room temperature and yield phosphonium salts. Upon protonation even di- and trications could be observed [88,89]. 

A supported version of Bi(0Tf)3-xH20 has been developed using a caffeine-derived salt, (l,3,7-trimethyl-9-ethylxanthinium b A(trifluoromethanesultonyI)-amide), as adsorbant. This compound has been prepared by direct alkylation of caffeine with ethyl triflate, followed by metathesis with LiNTf2) (Scheme 4) [59]. 

High polymers are generally obtained on treatment with Lewis acids at low temperatures in an inert solvent. Boron trifluoride and boron trifluoride etherate are the most widely used catalysts, but a small amount of water must be present, which is termed a promoter triethylaluminum and triisobutylaluminum are also useful initiators and are generally used with addition of water. Alkylating agents, such as ethyl triflate, triethyloxonium tetrafluoro-borate and hexafluorophosphite, and 2-methyl-l,3-dioxolenium perchlorate, are also effective initiators (76MI51301,72MI51304). 

Bates and Taylor reported the dialkylation of ketone o a -chanions using alkyl triflates (Table 6)30. Reactions of the dianions with methyl and ethyl triflates gave usee -alkylated... 

Initiation of THF with ethyl triflate leads to ethylated THF observed directly by H-NMR > ... 

For example, when ethyl triflate (C2HSOSO2CF3) is reacted with THF in CD3NO2 solvent at 25 °C at (IJo = (M)o = 2.0 mole I" -, only the formation of the ethyltetrahydrofuranium ion is observed without any subsequent propagation ... 

The values of kg are then determined separately (cf. Sect. Ill) and when the appropriate values of kg and kp (for a given (3 value since both constants depend on the polarity of the medium) are introduced into Eq. (99), the broken line 1 is obtained. It coincides quite well with the experimental solid line 1. This agreement between two lines simply means that k < kg, i.e. that the rate constant of the addition of THF to the macroester (macrotriflate) is not larger than the rate constant of the addition of THF to ethyl triflate. Indeed, if larger values of kp are inserted to Eq. (99) (e.g. kp = 5 kg, 10 kg and 10 kg, these values corresponding to broken lines 2, 3 and 4 in Fig. 11), then the experimental points of line 1 cannot be fitted any more to these calculated lines. 

Another group working on the same problem has come to different conclusions, namely that in the reaction with THF the macroester is much more reactive than low-molecular esters like ethyl triflate ... 

The reduction of a fuUy elaborated oxazolium salt and subsequent trapping of the azomethine ylide allowed Vedejs and co-workers" ° to complete their synthesis of aziridinomitosene. Alkylation of 1121 with 2-(phenylsulfonyl)ethyl triflate produced the oxazolium salt 1122, which was converted to the key bicyclic... 

A soln. of startg. hydroxamic acid in dichloromethane treated with a 20% molar excess of methyl triflate at room temp, for 48 h - intermediate nitrone hydrotriflate (Y 95%), in deuteriochloroform deprotonated with a 20% molar excess of triethylamine methyl N-(l,l-dimethylethyl)-benzenecarboximidate N-oxide (Y 85% overall). The products are relatively unstable, being converted to 1-functionalized nitrones with a variety of nucleophiles. F.e., also with ethyl triflate, and deprotonation on silica gel or with the weakly basic anion exchange resin. Bio-rad AG3-X4, s. J.A. Warshaw et al., J. Org. Chem. 54, 1736-43 (1989). 

The alkylation reactions proceed with moderate to good yields with primary iodides (Entries 1,3,6, and 7) or bromides (Entries 2,4, and 5) in the absence of additives or polar solvents. The only byproducts detected were small amounts of ( )-a- and P-A -phthaloyl alanines and ( )-A -phthaloyl aspartic acid. In a few instances, small amounts of A Vinylphthalimide, resulting from double decarboxylation, were also detected. Shorter reaction times were required when the reaction was performed at 40 °C. Secondary iodides also gave alkylated derivatives (Entries 8 and 9). However, no alkylation was observed when more hindered substrates, such as a-cholestanyl iodide and menthyl iodide or bromide were used. These halides were recovered unchanged or suffered elimination to afford mixtures of alkenes after several days at room temperature. On the other hand, no alkylation took place with methyl p-toluenesulfonate, ethyl triflate, and propylene oxide under the same reaction conditions. Similarly, alkenyl and aiyl halides were unreactive with nickelacycles. 

The direct alkylation of caffeine by ethyl triflate gave l,3,7-trimethyl-9-ethylxanthinium triflate, which led to 1,3,7-trimethyl-9-ethylxanthinium bis(trifluoromethanesulfonyl)amide after metathesis with LiNTf2. This ionic liquid proved to be an efficient system that can be used for the recycling of Hf(OTf)4. This reusable catalyst proved to be an efficient Lewis acid for Diels-Alder reactions leading to very little or no polymerization of the diene (eq 14). ... 

---