In general, Friedel-Crafts reaction is incompatible with amines due to the Lewis acidity of the catalysts. Recently, we reported that cyclic diaminocarbene-Gold(I) can be used as catalyst for the Friedel-Crafts alkylation between aromatic amines and alkenes. Herein, a systematically theoretical research was performed on this rare Friedel-Crafts reaction. The adopted calculation method is accurate enough to reproduce the crystal structure of the catalyst. It was found that the reactions followed the electrophilic aromatic substitution mechanism. The gold cation can activate the C=C double bond and generate the electrophilic group which can be attacked by the aromatic ring. The para-product is more energy favorable which agrees well with the experimental results. The reaction of α-methylstyrene follows the Markovnikov rule, and the activation energy to generate the branched product of methylstyrene is lower than that producing the linear product. However, the reaction of butanone follows the anti-Markovnikov rule, and the activation energy to generate the branched product of butanone is higher than that producing the linear product. These calculation results reveal the mechanism of this new Friedel-Crafts reaction. It can well explain the high para-selectivity and the substrate-dependent of the product structures in the experiment.

Abstract In the presence of HF-SbF5 super acid, the alkylation of acetophenone with various alkyl chlorides was investigated. The products were found to be those of m-alkylated acetophenone derivatives and their related compounds in fairly good yields. The relative reactivity of alkyl chlorides was in the order of EtCl>n-, iso-PrCl, n-, s-BuCl>>iso-BuCl>>t-BuCl. The formation of olefinic, alcoholic, and condensation products observed in the reaction with propyl chlorides, and skeletal isomerization products obtained in the reaction with butyl chlorides was also discussed.

While aromatic diazonium salts are important reagents in organic synthesis, 'Diazonium ions generated from ordinary aliphatic primary amines are usually useless for preparative purposes, since they lead to a mixture of products giving not only substitution by any nucleophile present, but also elimination and rearrangements if the substrate permits.'¹ In this work, we report that this statement is no longer valid, and it is now possible to control diazotization of aliphatic amines by utilizing isopentyl nitrite in HFIP. This transformation enabled electrophilic aromatic substitution with these highly abundant and commercially available alkyl reagents, as well as transforming them into building blocks typically employed in organic synthesis. The methodology opens an avenue for reactions involving aliphatic amines, even such demanding substrates as amino acids, as a source of carbocations thus expanding the degree of chemical space.

Friedel-Crafts alkylation The Friedel-Crafts alkylation is a name reaction in organic chemistry. It is used to add alkyl groups to aromatic rings using a Lewis acid like aluminium chloride as a catalyst. Materials The Friedel-Crafts alkylation starts with an aromatic compound like benzene (C6H6) and an alkyl halide like ethyl chloride (CH3CH2Cl). A small amount of a Lewis acid, usually aluminium chloride, is added to be a catalyst. Alkenes can be used in place of alkyl halides by using a Brønsted acid as the catalyst. This version of the reaction is common in the chemical industry. Mechanism The Friedel-Crafts alkylation is a type of electrophilic aromatic substitution with two carbocation intermediates.[1] First, the alkyl halide reacts with the catalyst, making a carbocation and an anionic Lewis adduct: - CH3CH2Cl + AlCl3 → CH3CH+2 + AlCl−4 If starting from an alkene and Brønsted acid, the carbocation is instead made from protonation of the alkene: - H2C=CH2 + H2SO4 → CH3CH+2 + HSO−4 The carbocation is a strong electrophile, so it is attracted to the many electrons in the aromatic ring.

This, and other compounds similar to it, formed a group called aromatic compounds. They were named aromatic due to their pleasing aroma, although not all smelled as such. The unusual stability of benzene makes it ideal for many reactions. Among these reactions is one known as the Friedel-Crafts Alkylation. However, the reaction suffers from a group of limitations making it a poor candidate to achieve desired results. Friedel-Crafts Alkylation was first discovered by French scientist Charles Friedel and his partner, American scientist James Crafts, in 1877. This reaction allowed for the formation of alkyl benzenes from alkyl halides, but was plagued with unwanted supplemental activity that reduced its effectively. - Carbocation Rearrangement - Only certain alkylbenzenes can be made due to the tendency of cations to rearrange. - Compound Limitations - Friedel-Crafts fails when used with compounds such as nitrobenzene and other strong deactivating systems. - Polyalkylation - Products of Friedel-Crafts are even more reactive than starting material.