Trimethylsilyl Pentafluorophenylbis(trifluoromethanesulfonyl)methide as a Super Lewis Acid Catalyst for the Condensation of Trimethylhydroquinone with Isophytol

Abstract

Acid and vitamin E: Trimethylsilyl super Lewis acids, such as [C6F5C(Tf)2]− Me3Si+ and Tf3CSiMe3, are extremely active and highly effective catalysts for the regioselective condensation of trimethylhydroquinone with isophthyol to afford (±)‐α‐tocopherol (vitamin E; see scheme, Tf=CF3SO2.

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

“…11). From a chemical and biological point of view, -tocopherol is the most active form of Vitamin E group [36][37]. This reaction is not only a good test for the acid site types but is also interesting from an economical point of view, due to the high market demand for this compound and the various environmental problems that industry faces with the currently used homogeneous catalysts.…”

Synthesis of (all‐rac)‐α‐Tocopherol in Supercritical Carbon Dioxide: Tuning of the Product Selectivity in Batch and Continuous‐Flow Reactors

“…Since the condensation of 2 and 3 to 1 possibly proceeds through Friedel-Crafts alkylation-cyclization [4,7,8,10a,12] or an orthoClaisen rearrangement of an intermediary allyl ester, [13,14] the use of non-polar reaction media would suppress the formation of the secondary cation from 3, to minimize the formation of the undesired five-membered by-products 4. In fact, it has been reported that the selectivity of 1 attained in a non-polar solvent, heptane, is markedly improved, [2] while the chemical yield of 1 is maximized in polar aprotic solvents. [4,10a] Thus, the reaction chemistry of the condensation to 1 in…”

“…We first measured the solubility of the fluorinated catalyst 5a as well as the substrates 2 and 3 in scCO 2 . The catalyst 5a proved to be fairly soluble in scCO 2 ; the solubility was estimated to be 5.0 mmol/L by 19 F NMR spectroscopy [17] under supercritical conditions, 40 8C and 8.5 MPa.…”

“…[2 -10a] There still remain serious drawbacks including the low catalytic activities and the formation of by-products, benzofuran derivatives 4, which are difficult to separate from the desired product 1. [2] Supercritical carbon dioxide (scCO 2 ) as a reaction medium is an attractive alternative to organic solvents because of its low toxicity and ease of separation from the product and catalyst. [11] In addition to these environmental benefits, scCO 2 has the pressure-tunable physical properties as a reaction medium such as the solubilizing ability, which would affect the outcome of reactions in terms of the reactivity and selectivity.…”

“…In order to efficiently and economically access this important compound, a number of catalytic synthetic procedures using polymer-supported catalysts [2,3] and solid acid catalysts [4] as well as unorthodox reaction media such as supercritical fluids, [5] have been examined. [2 -10a] There still remain serious drawbacks including the low catalytic activities and the formation of by-products, benzofuran derivatives 4, which are difficult to separate from the desired product 1.…”