(Z)-1-Aryl-1-haloalkenes as intermediates in the Vilsmeier haloformylation of aryl ketones

[reaction: see text] Vilsmeier reagents give (Z)-1-aryl-1-haloalkenes from aryl ketones bearing an electron-donating substituent at the ortho- or para-position. These haloalkenes are intermediates in the Vilsmeier haloformylation of the aryl ketones. Another reaction mechanistic pathway is thus available in certain Vilsmeier haloformylations, in competition with the commonly accepted route by way of an enaminoketone.     

Pyrrolocarbazoles. 4. Acetylation of 3H-pyrrolo[2,3-c]carbazole

It is shown that 1-acetyl and 1-chloroacetyl derivatives are formed in the Vilsmeier acylation of 3H-pyrrolo[2,3-c]carbazole. The 3,6-diacetyl derivative is formed by the action of Ac₂O without a catalyst, whereas the presence of catalytic amounts of H₃PO₄ leads to 1,6-diacetyl-3H-pyrrolo[2,3-c]carbazole. Only one reaction product, viz., the 9-acetyl derivative, is formed when AlCl₃ is used as the catalyst, while a mixture of acylation products was obtained in the presence of SnCl₄.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 497–500, April, 1980.     

One-pot synthesis of 1,3,4-thiadiazoles using Vilsmeier reagent as a versatile cyclodehydration agent

A simple and efficient synthetic method for the one-pot synthesis of 1,3,4-thiadiazoles utilizing Vilsmeier reagent was developed. In this method carboxylic acids and hydrazine were converted to 1,3,4-thiadiazoles in the presence of Vilsmeier reagent and Lawesson's reagent. The influence of the thionation reagent, solvent, temperature and time, in this reaction was discussed. The developed methodology for 1,3,4-thiadiazole synthesis has the advantage of simplicity, ambient reaction conditions, easy purification and good to excellent yield of products.     

Preparation of 2-formyl-4-nitropyrroles

The Vilsmeier reaction of 3-nitropyrroles which are prepared by the reaction of nitroalkenes with the sodium salt of tosylmethylisocyanide gives 2-formyl-4-nitropyrroles in good yields.     

Reaction of Tröger’s base analogues with Vilsmeier reagents

As part of a program aimed at introducing functionality onto the Tröger’s base framework post-synthesis, we investigated the formylation reaction of Tröger’s base analogues with Vilsmeier reagents. We found that rather than the anticipated reaction at the aryl rings, these compounds react with Vilsmeier reagents to afford compounds with a modified strap, whereby the apical methylene group is replaced by a methylene strap bearing an N,N-disubstituted amine.     

Reactions of 1-Substituted Benzo[4,5]imidazo[1,2-a]pyridines

Bromination of 1-oxo(imino, amino)benzo[4,5]imidazo[1,2-a]pyridines gave the corresponding 2-bromo derivatives. Acylation using the Vilsmeier complex in acetic anhydride gave the N-formyl and N-acetyl derivatives. The reaction of the amine with the Vilsmeier complex, acetyl acetone, ethyl acetoacetate, and 2,5-dimethoxytetrahydrofuran occurs at the amino group.     

Synthesis of novel quinoline analogues of nimesulide: An unusual observation

Reduction of nimesulide followed by treating the N‐acyl derivative of resulting arylamine with Vilsmeier‐Haack reagent provided novel 2‐chloro‐3‐formylquinoline derivatives. The construction of quinoline ring using Vilsmeier‐Haack reagent afforded an unexpected compound, N‐(2‐chloro‐3‐formyl‐7‐phenoxy quinolin‐6‐yl)formamide, in addition to the expected product. The structure of this unexpected quinoline derivative was established via single‐crystal X‐ray analysis and its formation could be explained by an unprecedented N‐S bond cleavage under Vilsmeier‐Haack reaction conditions. The 2‐chloro‐3‐formylquinoline derivatives obtained were converted to a number of corresponding Schiff bases with potential pharmacological importance. J. Heterocyclic Chem., 2011.     

The Chemistry of Dichloromethylenammonium Salts (“Phosgenimonium Salts”)

Dichloromethylenammonium salts, particularly dichloromethylenedimethylammonium chloride, occupy a unique place as stable but reactive building blocks for synthesis. They contain three mobile chlorine atoms activated by an amino group on the same carbon atom. These salts can be regarded as chlorinated Vilsmeier or Mannich reagents and are thus at a higher oxidation level. As in the Mannich or Vilsmeier reaction, the carbon condenses here as an electrophile with formation of C? C or C? hetero atom bonds in a variety that is still far from being exhausted.     

Vilsmeier formylation of 5,10,15-triphenylcorrole: expected and unusual products

5,10,15-Triphenylcorrole (1) reacts with the Vilsmeier reagent (POCl(3)/DMF) to give the corresponding 3-formyl derivative 3 as the major product. The regioselectivity of the reaction was proven by X-ray crystallography and only traces of the 2-formyl isomer were observed. A more polar product is also observed and this compound becomes the major product when an excess of DMF is used for the preparation of the Vilsmeier reagent, while the formation of the 3-formyl isomer is almost completely suppressed. X-ray crystallography allowed us to identify this compound as the fully substituted N-ethane bridged derivative 4, formed from the attack of the Vilsmeier reagent at the inner core of the macrocycle. This compound is unique among porphyrinoid macrocycles, and further confirms the peculiarity of corrole chemistry.     

A novel synthesis of benzofuran and related compounds. I. The vilsmeier reaction of phenoxyacetonitriles

A novel synthesis of 2-benzofurancarboxylic acid derivatives by the Vilsmeier reaction of phenoxyacetonitriles is described.     

A new synthesis of fervenulin 4-oxide

The reaction of 1,3-dimethyl-6-hydrazino-5-nitrosouracil (1) with Vilsmeier reagent (dimethylformamide-phosphorus oxychloride) afforded fervenulin 4-oxide (II) in good yield.     

A novel synthesis of benzofuran and related compounds. III. The vilsmeier reaction of phenoxyacetaldehyde diethyl acetals

A novel synthesis of 2-benzofurancarbaldehydes by the Vilsmeier reaction of phenoxyacetaldehyde diethyl acetals is described.     

A Convenient Method for the Preparation of Nitriles from Aldehydes and Aldoximes

Nitriles were prepared from their corresponding aldehydes or aldoximes with the Vilsmeier reagent in a one-pot reaction or without another solvent at room temperature in 74-98% yields.     

Formylporphyrins and their derivatives in the chemistry of porphyrins (review)

Data on the synthesis and chemical transformations of formylporphyrins obtained with the Vilsmeier reaction are generalized in the review. Special attention is focused on synthesis of dimeric porphyrins.     

Facile and selective synthesis of chloronicotinaldehydes by the Vilsmeier reaction

Eleven enamides were prepared by adopting different procedures. The various enamides prepared were subjected to Vilsmeier reaction using (i) POCl₃/DMF; (ii) diphosgene/DMF; (iii) triphosgene/DMF leading to the formation of various multisubstituted chloronicotinaldehydes. Studies carried out indicate that Vilsmeier reagent concentration and the replacement of POCl₃ by diphosgene or triphosgene, provides excellent selectivity and higher yields. Under modified reaction conditions one can get only chloronicotinaldehydes and not the chloropyridines as products. The various advantages in using diphosgene and triphosgene are illustrated. The mechanism of formation of chloronicotinaldehyde was discussed.     

Synthesis of tetra-substituted furan derivatives from 1-arylpropane-2,3-diones

1-Arylpropane-2,3-diones 4 gave 2-dimethylamino-3-formyl-4-chloro-5-arylfuran derivatives 7 in the Vilsmeier reaction.     

Unprecedented Vilsmeier formylation: expedient syntheses of the cruciferous phytoalexins sinalexin and brassilexin and discovery of a new heteroaromatic ring system

[reaction: see text]. A very concise first synthesis of sinalexin was achieved by regioselective formylation of 1-methoxyindoline-2-thione under Vilsmeier conditions followed by unprecedented ammonia workup. Similar formylation of indoline-2-thione yielded brassilexin and a novel pentacyclic heteroaromatic compound resulting from condensation of the Vilsmeier adduct of indoline-2-thione. Both sinalexin and brassilexin displayed strong antifungal activity against several pathogens of crucifers.     

A ‘One-Pot’ Synthesis of Substituted 3-Carboethoxy-2-Methylquinolines from Ethyl Acetoacetate

A ‘one-pot’ synthesis of 3-carboethoxy-2-methyl-quinolines from ethyl acetoacetate via successive reaction with Vilsmeier reagent and anilines is described.     

Synthesis and properties of Schiff bases of mesoformylporphyrins (Review)

A summary is presented on the use of intermediate immonium salts formed in the Vilsmeier reaction in porphyrin chemistry for the synthesis of various Schiff bases of mesoporphyrins. Special attention is given to the formation and properties of porphyrins with a five-membered exocycle.     

Synthesis of 2-(5-hydroxymethyl-2-formylpyrrol-1-yl)propionic acid lactone

2-(5-Hydroxymethyl-2-formylpyrrol-1-yl)propionic acid lactone was synthesized in six steps with a 17.0% overall yield, starting from L-alanine. The synthetic route involved the Clauson-Kaas reaction, Vilsmeier reaction, and transesterification. The transesterification was the key step in the formation of the target compound.