3.5 – The Vilsmeier–Haack Reaction

摘要: The classical Vilsmeier-Haack reaction1,2 involves electrophilic substitution of a suitable carbon nucleophile with chloromethyleneiminium salt, for example salt (1). Suitable nucleophiles are generally electron-rich aromatic compounds such as N.N′-dimethylaniline (2), alkene derivatives styrene (3) or activated methyl methylene 2,4,6-trinitrotoluene (4; Scheme 1). These (2–4) react (1) giving, after loss hydrogen chloride, the corresponding iminium salts (5–7). Hydrolysis (5) affords aldehyde derivative (8) and this transformation (ArH → ArCHO) is well-known formylation reaction. (6) similarly yields formylated product (9). Compounds that possess groups (4) giving like (7). Proton from (7) enamine (10), which can participate in further reaction vinylamidinium (11). (11) malondialdehyde