Vilsmeier complex

Another type of elimination reaction is the reaction of 1 -(5-methyl-1 -phenyl- H-pyrazol-4-yl)ethanone with a Vilsmeier complex to give 3-chloro-3-(5-methyl-l-phenyl-l//-pyrazol-4-yl)propenal, which in turn undergoes dichloroformylation... 

In an initial step the reactive formylating agent is formed from N,N-dimethylformamide (DMF) 2 and phosphorus oxychloride. Other N,N-disubstituted formamides have also found application for example A -methyl-A -phenylformamide is often used. The formylating agent is likely to be a chloromethyl iminium salt 4—also called the Vilsmeier complex (however its actual structure is not rigorously known)—that acts as the electrophile in an electrophilic substitution reaction with the aromatic substrate 1 (see also Friedel-Crafts acylation reaction) ... 

Several catalysts have been recommended for the N-acetylation of carbazole with acetic anhydride boron trifluoride, phosphorus pentoxide, concentrated sulfuric acid, zinc chloride, and phosphoric acid all gave 9-acetylcarbazole in moderate to good yield. 9-Acetylcarbazole can also be prepared using the Vilsmeier complex of N,N-dimethylacetamide and phosgene. ... 

N, A -dimethylformamide (DMF). This reaction proceeds by formation of the electrophilic Vilsmeier complex, followed by electrophilic substitution of the heterocycle. The formyl group is generated in the hydrolytic workup. 

Benzal chlorides. Benzaldehyde or the bisulfite addition product reacts with thionyl chloride and DMF at -10 20° to form benzal chloride, QHsCHCU, in 88% yield. Newman favors structure 1 for the Vilsmeier complex involved in this reaction. This reaction is general for aromatic aldehydes and a, -unsaturated aldehydes. The reaction is not observed with diaryl ketones. 

Although amides are the least reactive of the common acid derivatives under most circumstances, they are involved in several reductive syntheses of aldehydes. As described below the conversion can be accomplished by one-electron reducing agents (though relatively powerful ones), and there are specific types of amide which can be caused to decompose to aldehydes. Moreover, amides are precursors of imi-doyl chlorides, Vilsmeier complexes and thioamides, which can also be reduced to aldehydes as discussed in later sections. 

Finally, treatment of amides with phosphorus oxychloride gives Vilsmeier complexes, which are often formulated as A-alkylated imidoyl chlorides (59). Irrespective of their precise nature, it has been found that they can be converted very efficiently to aldehydes by reduction with zinc followed by aqueous work-up (Scheme 17). Although the method has only been used for benzaldehyde and a number of chlorinated and brominated analogs, the yields reported are consistently high (87-97%). ... 

Sridhar, R., Perumal, P. T. Synthesis of acyl azides using the Vilsmeier complex. Synth. Commun. 2003, 33, 607-611. 

The Vilsmeier complex prepared from dimethylformamide and phosphoryl chloride has been used as a C, unit to cyclize 5-acetyl-6-amino-l,3-dimethyluracil. Subsequently, the resulting 5-hydroxy group is converted into achloro substituent by the same reagent. Thus, after 2 hours at 60°C, 5-chloro-l,3-dimethylpyrido[2,3-c/]pyrimidine-2,4(l//,3A)-dione (26) is obtained.183... 

The Vilsmeier reaction between 2,4-dimethoxytoluene and the Vilsmeier complex of P0CI3 and N-methylformanilide gave the benzaldehyde (mp 117-118 deg C) with a yellow malononitrile derivative from EtOH with a mp of 193-194 deg C. The nitrostyrene from this and nitroethane formed yellow crystals from CH3CN, with a mp 138-139 deg C. The amine formed easily with LAH in ether, and the product F-310 (or 5-DOM) gave white crystals from CH3CN with a mp of 182-183 deg C. 

Reduction of amides and imides to amines. Tertiary amides (1) can be reduced to amines (3) by conversion to the Vilsmeier complex (2) followed by reduction with NaBHi. The method is applicable to secondary amides, (4) -> (6), but primary amides are converted into nitriles. ... 

An indirect method for the reduction of amides to amines by NaBHa (applicable only to tertiary amides) involves conversion into a Vilsmeier complex [(R2N=C(C1)R)+C1 ], by treatment with Phosphorus Oxychloride, followed by its reduction. In a related methodology, primary or secondary (also cyclic) amides are first converted into ethyl imidates by the action of Triethy-loxonium Tetrafluoroborate, and the latter reduced to amines with NaBHa in EtOH or, better, with NaBHa-Tliiif/V) Chloride in Et20. ... 

Dimethoxytoluene allowed to react with a Vilsmeier complex prepared in situ from dry dimethylformamide and POCL -> 2,4-dimethoxy-3-methylbenz-aldehyde (Y 83%) refluxed 24 hrs. with m-diloroperoxybenzoic acid in dry methylene chloride, and the intermediate formoxy compd. hydrolyzed under Ng with aq.-alc. KOH (cf. Synth. Meth. 17, 338) -> 2,4-dimethoxy-3-methylphenol (Y 96%). F. e. s. I. M. Godfrey, M. V. Sargent, and J. A. Elix, Soc. Perkin I 1974,1353. 

A soln. of POBrg in anhydrous chloroform added slowly at 0° with vigorous stirring to a dry mixture of dimethylformamide and chloroform, the resulting suspension of the Vilsmeier complex stirred and treated at 0° with 3-methyl-4-(2-methoxycarbonylethyI)-2-pyrrolinone in chloroform, and kept 3 hrs. at 45° 4- methyl - 3 - (methoxycarbonylethyl) - 5- bromo - 2-(N,N-dimethylaminomethyl ene)-2H-pyrrole (Y 80%) dissolved in a small amount of glacial acetic acid, and treated with as much water as necessary to keep the heated soln. clear 4 - methyl -3-(2-methoxycarbonylethyl)-5 - bromopyrrole - 2 - carboxaldehyde (Y 95%). F. e. s. H. V. Dobeneck and T. Messersdimitt, A. 751, 32 (1971) reactions of the products cf. ibid. 751, 40 review of 2-pyrrolones cf. G. Rio and D. Masure, Bl. 1972, 4598 cf. ibid. 1972, 4604, 4610. 

Amides have been converted in high yield into secondary and tertiary amines by reduction of first-formed Vilsmeier complexes with sodium borohydride. The ability of triphenylpyridine to act as a good leaving group has been exploited in a... 

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