Anions boron triflates

The aldol reactions introduced thus far have been performed under basic conditions where enolate species are involved as the reactive intermediate. In contrast to the commonly accepted carbon-anion chemistry, Mukaiyama developed another practical method in which enol species can be used as the key intermediates. He is the first chemist to successfully demonstrate that acid-catalyzed aldol reactions using Lewis acid (such as TiCU) and silyl enol ether as a stable enol equivalent can work as well.17 Furthermore, he developed the boron tri-fluoromethane sulfonate (triflate)-mediated aldol reactions via the formation of formyl enol ethers. 

The overall mechanism is closely related to that of the other cross-coupling methods. The aryl halide or triflate reacts with the Pd(0) catalyst by oxidative addition. The organoboron compound serves as the source of the second organic group by transmetala-tion. The disubstituted Pd(II) intermediate then undergoes reductive elimination. It appears that either the oxidative addition or the transmetalation can be rate-determining, depending on reaction conditions.134 With boronic acids as reactants, base catalysis is normally required and is believed to involve the formation of the more reactive boronate anion.135... 

There are many other ways of making boronic acids and you are referred to Suzuki s review37 for a full discussion. A Suzuki coupling would occur if one of these boron compounds 236 was combined with an aryl or vinyl halide or triflate in the presence of Pd(0) and an oxy-anion. 

Carbathioferrocenophane, 47, underwent cationic ROP with methyl triflate and boron trifluoride etherate, but was resistant to both anionic and transition-metal-catalyzed ROP.100101 However, cationic ROP initiated with methyl triflate caused oxidation of the iron centers in the polymers. Me+ and H+ were determined to initiate cationic ROP for the methyl triflate and boron trifluoride, respectively.101 Scheme 2.12 shows a proposed mechanism of the methyl triflate, 48, initiated ROP of [2]carbathioferrocenophane, 47. 

Indoles react with epoxides and aziridines in the presence of Lewis acids (see 20.4.1 for reaction of indolyl anions with such reactants) with opening of the three-membered ring and consequent 3-(2-hydroxyethylation) and 3-(2-aminoethylation) of the heterocycle. Both ytterbium triflate and phenylboronic acid are good catalysts for reaction with epoxides under high pressure silica gel is also an effective catalyst, but reactions are slow at normal pressure and temperature. Reaction with aziridines can be catalysed by zinc triflate or boron trifluoride. °... 

Reaction with boronates and aryUrismutii triflates. Dialkyl 2,3-butadienylboronates, which serve as l,3-butadiene-2-yl anion equivalents, are formed from allenylmagnesium bromide with dialkyl (halomethyl)boronates. ... 

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