Alkylation with Carbonyl Compounds and Derivatives

Carbonyl compounds, particularly aromatic aldehydes, when activated with electrophilic catalysts, can also react with aromatics.241 The process is often called condensation or reductive alkylation, but it is actually a multistep Friedel-Crafts alkylation reaction. 

Olah et al.242 and Shudo and co-workers243 have shown that benzaldehyde reacts with benzene in various superacidic systems [triflic acid, triflic acid-SbF5, 

Catalyst Time (min) Conversion (%) Rate0 Selectivity paralmeta 

Reaction conditions 5 ml of toluene, 1 mmol of 1-bromoadamantane, 0.2 g of catalyst, 111°C. Initial reaction rate, mmol (gcat min)-1. 

Fukuzawa et al.245 used 2-phenyl- 1,3-dioxane to benzylate a variety of arenes [Eq. (5.91)]. Similar observations were made when substituted benzaldehydes were treated in the presence of 1,3-propanediol under identical conditions. Although 2-phenyl-1,3-dioxane gave similar results, benzaldehyde dialkylacetals in general were unreactive under similar conditions. Mechanistic studies including reaction of a labeled dioxane indicate the involvement of the alkylated intermediate 65 and product formation was interpreted via an 1,3-hydride shift. 

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