Aldehydes Vilsmeier reagent

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

In contrast to iV-disubstituted 3-hydroxyanilines which react with Vilsmeier reagent to give AWisubstituted salicylaldehydes, their heteroanalogous iV-disubstituted 2-amino-4-hydroxythiazoles (60) react with Vilsmeier reagent to give iV-disubstituted 2-amino-4-chlorothiazole-5-aldehydes (61) <96JPR51>. 

Amino groups react very easily with aldehydes or ketones, and with aldehydes in the presence of amines, they can be acylated by the usual acylating agents, and they react with amidacetals, Vilsmeier reagents and nitroso compounds (Scheme 12). As mentioned earlier, alkylation leads mainly to AT(2)-alkylated products. The hydrazino group reacts in the same way as the amino group with aldehydes or ketones, with acyl chlorides or carboxylic anhydrides, with sulfonyl chlorides, ortho esters, carbon disulfide and with nitrous acid. The last three reactions have mainly been used for the synthesis of condensed 1,2,4-triazines. 

RCOOH — RCHO. The iminium salt (1) formed on reaction of a carboxylic acid with the Vilsmeier reagent (formed from DMF and oxalyl chloride) is reduced by lithium tri-/-butoxyaluminum hydride (1 equiv.) to an aldehyde. The chemo-selectivity is noteworthy ester, nitrile, keto, and halide groups are not affected.3... 

Vilsmeier reagent, reaction with ketones to form 0-chloro- ,3-unsaturated aldehydes, 46,19... 

The Vilsmeier reagent gave 3-carboxaldehydes of 1-phenyl-(76%), 1-butyl- (48%), and 6-chloro- (25%) -4-methyl-7-azaindoles. The aldehydes can also be obtained from the grammes, and this is the way in which 7-azaindole- and 4-methyl-7-azaindole-3-carboxaldehydes were prepared (see Section IV,F,1). 

Formylation of Hmoneae. (-i-)-(4R)-Limonene (1) is formylated by the Vilsmeier reagent (2) stereoselectively to give mainly the (E)-of,)3-unsaturated aldehyde 3. The product was used tor the synthesis of (4R),(E)-a-atlantone (5), a sesquiterpene from Cedrus oils. 

Cyanomethyl groups can be a convenient source of pyridine rings treatment with acetic anhydride-perchloric acid [3934], acetonitrile-aluminium chloride [2884], Vilsmeier reagent [2727], a 1,3-diketone (or its enol) [2714] and malon-aldehyde bisacetal [2714] have been used successfully and sometimes give high yields. Pyrido[4,3-A]indoles have been reviewed [2535]. 

The interaction of oxindole with the Vilsmeier reagent produces 2-chloro-3-formylindole efficiently this difunctional indole has considerable potential for elaboration, for example nucleophilic displacement of the halogen, activated by the orf/to-aldehyde, can produce indoles carrying a nitrogen substituent at C-2. ... 

Aryloxazole-4-aldehydes 59 (R = H, Me, Cl, Br or Ph) are formed in good yields in the reaction of 2-azidoacetophenones 58 with the Vilsmeier reagent dimethylformamide-phosphorus oxychloride <97TL6089>. A one-pot synthesis of the cyanooxazoleamines 60 is by the action of dicyclohexylcarbodiimide and pyridine on mixtures of aminonalononitrile tosylate and carboxylic acids <97S861>. 

An earlier investigation (23) demonstrated that the Vilsmeier-Haack reaction of the ArCOCHj type compounds gives the monoformylated compounds or the corresponding P-chloro-vinyl aldehydes. It was found, however, that in the case of o-hydroxyacetophenones, the methyl group was doubly formyl-ated by a Vilsmeier reagent to give our first target compounds, 4-oxo-4H-l-benzopyran-3-carboxaldehydes ( ) in one step ( 1, J ). The reason why double formylation took... 

The formylation of polyene aldehydes and o,jS-unsubstituted ketones with the Vilsmeier reagent (DMF-POCI3) has been reported recently. For example, reaction of the ketones XXIV with the Vilsmeier reagent produces the iminium salts XXV, which are hydrolyzed to the aldehydes XXVI. The latter compounds form the conjugated ene-yne derivatives XXVII upon addition of their dioxane solution to dilute sodium hydroxide at 80-90°C... 

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). ... 

Much of the research on Vilsmeier reactions in the past 50 years has focused on expanding the scope of this transformation. Whereas the reaction was once limited to electron-rich aromatics and heteroaromatics, aliphatic substrates have increasingly been found to react with Vilsmeier reagents. Furthermore, alternate transformations of the iminium intermediate to form products with functional groups other than aldehyde have been developed. Finally, access to a diverse range of heterocycles is now possible due to discovery of substrate classes that are capable of undergoing intramolecular annulation reactions on the iminium intermediate. 

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