Detailed Characterization ofp-Toluenesulfonic Acid Monohydrate as a Convenient, Recoverable, Safe, and Selective Catalyst for Alkylation of the Aromatic Nucleus

Abstract

Alkylation of the aromatic nucleus, an important reaction in industry and synthetic organic chemistry, has traditionally been carried out by the well-known Friedel-Crafts reaction employing Lewis acid catalysts such as AlCl 3 and BF 3 or by using highly reactive organometallic reagents. Although protic acids such as anhydrous HF and concentrated H 2 SO 4 have also been used in the alkylation of the aromatic nucleus, the notoriously corrosive, highly toxic, and hazardous nature of these agents has precluded their common use under ordinary laboratory conditions. Various organic sulfonic acids have, on occasion, been used as catalysts in Friedel-Crafts alkylations, but to our knowledge the chemistry and the scope of these reactions for common laboratory use have never been exploited in detail. In the present study we have characterized commercially available p-toluenesulfonic acid monohydrate (TsOH) as an efficient catalyst for the intermolecular coupling of the aromatic nucleus with activated alkyl halides, alkenes, or tosylates under mild conditions in an open atmosphere. In comparison to conventional Friedel-Crafts catalysts such as AlCl 3 , BF 3 , HF, and concentrated H 2 SO 4 , the extent of the formation of undesired products from side reactions such as transalkylation, polymerization, etc. was minimal with the TsOH-catalyzed reaction. The ability to recover and reuse the catalyst from the reaction mixtures, minimal generation of environmentally unfriendly waste, high specificity of the reaction, and the low cost of the catalyst are important advantages of the TsOH catalyst over the other conventional Friedel-Crafts catalysts.

Pressure Effects on Friedel–Crafts Alkylation Reactions in Supercritical Difluoromethane

“…A number of organic sulfonic acids have also been employed as effective catalysts in FC alkylations, including p-toluenesulfonic acid (p-Tos). [37] Anisole and toluene were chosen as the aromatic compounds herein because they are both liquids and they were observed to dissolve into solution quickly. Tert-butylchloride (t-BuCl) and tert-butylalcohol (t-BuOH) were chosen as the alkylating agents because, firstly, they are liquids and it was observed that they dissolve into solution readily and, secondly, they are tertiary compounds so rearrangement to a more stable carbocation will not occur.…”

Palladium-catalyzed desulfinylative C–C allylation of Grignard reagents and enolates using allylsulfonyl chlorides and esters

“…The spectral data ( 1 H NMR and 13 C NMR) of the product are identical with those described in the literature for this compound. 131 Using the general procedure 2 for the reaction using NaH (43 mg, 1.07 mmol, 1.5 equiv), methyl acetoacetate (0.13 g, 1.07 mmol, 1.5 equiv) with 2b (0.1 g, 0.72 mmol, 1 equiv): 100 mg (89%), colorless oil. Using the general procedure 1 for the reaction using 1.0 M soln of o-tolylmagnesium chloride (1.0 mL, 1.0 mmol, 1.5 equiv) with 2c (0.1 g, 0.65 mmol, 1 equiv): 65 mg (69%), colorless oil.…”

A Copper(II) Triflate‐Catalyzed Tandem Friedel–Crafts Alkylation/Cyclization Process towards Dihydroindenes

“…Allylic halides possess two reactive centers susceptible to Friedel-Crafts alkylation, and the regioselectivity largely depends on the catalyst chosen. For example, it is known that with protic acid catalysts, haloalkenes generally favor the reaction at the double bond, [10,11,12] while reactions at the allylic position can be realized by some ruthenium catalysts. [13] In this report, the efficiency and the regioselectivity of the Friedel-Crafts alkylations between substituted benzenes and allylic halides with CuA C H T U N G T R E N N U N G (OTf) 2 as catalyst were examined.…”