Amides Vilsmeier-Haack reaction

The reaction with disubstituted formamides and phosphorus oxychloride, called the Vilsmeier or the Vilsmeier-Haack reaction,is the most common method for the formylation of aromatic rings. However, it is applicable only to active substrates, such as amines and phenols. An intramolecular version is also known.Aromatic hydrocarbons and heterocycles can also be formylated, but only if they are much more active than benzene (e.g., azulenes, ferrocenes). Though A-phenyl-A-methyl-formamide is a common reagent, other arylalkyl amides and dialkyl amides are also used. Phosgene (COCI2) has been used in place of POCI3. The reaction has also been carried out with other amides to give ketones (actually an example of 11-14),... 

Another useful method for introducing formyl and acyl groups is the Vilsmeier-Haack reaction.61 An Ac. V-di alkyl amide reacts with phosphorus oxychloride or oxalyl chloride62 to give a chloroiminium ion, which is the reactive electrophile. 

Acylpyrroles can also be prepared by using the Vilsmeier reaction with various amides. Excellent yields of 2-aroylpyrroles were obtained using morpholides instead of the more common N,N- dimethylamides (equation 178) (77JOC4248). Similarly, a variety of 3-acylin-doles have been prepared using the Vilsmeier-Haack reaction (79HC(25-3)357). 

Lactams represented by the general structure (120 R = H) are /V-formylated to give products (120 R = CHO) in the Vilsmeier-Haack reaction unless the amide has an available a-hydrogen atom in which case products (121) and (122) are formed (see Section 3.S.S.3). ... 

When a dialkyl amide is treated with phosphorus oxychloride a Vilsmeier-Haack reagent (hereafter Vilsmeier reagent) is formed. Subsequent treatment with an electron-rich n system leads to substitution and formation of an intermediate iminium ion, which can be hydrolyzed to yield an aldehyde. The overall process is known as a Vilsmeier-Haack reaction (hereafter Vilsmeier reaction). ... 

The Vilsmeier (or Vilsmeier-Haack or Vilsmeier-Haack-Arnold) reaction is primarily a mild method for formylating a wide variety of substrates.1 It has limited application to higher acylation and involves the reaction of a Vilsmeier reagent derived from a tertiary amide and an acid chloride (or occasionally a bromide). The most commonly employed amide is jV,N-dimethylformamide (DMF) and the acid chloride is generally phos-phoryl chloride, though phosgene and thionyl chloride are also employed. 

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