Vilsmeier Formylation of 4-Dimethylaminostilbene

Seus, Edward J.

doi:10.1021/jo01019a076

Cited by 8 publications

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“…UV and electron spin resonance (ESR) spectroscopy indicate that the electronic properties of poly-(thiophenes) and other poly(heterocycles) are dictated by the carbon backbone alone and that the role of the heteroatom is subordinate (Ford et al, 1982;Tourillon, 1986). Preliminary investigations (Seus, 1965) had suggested similar behaviour for other heterocyclic arylenevinylene oligomers. A deformation electron density study, based on high-quality singlecrystal X-ray diffraction intensities, is the ideal tool to gain information about the molecular %-systems of the latter type of compound and to test the suggestion above regarding similar behaviour.…”

Section: Introductionmentioning

confidence: 67%

Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal

Blockhuys¹,

Velde²,

Maes³

et al. 2003

Acta Crystallogr Sect B

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The crystal structure of E-1,2-bis(3-methoxy-2-thienyl)ethene (C12H12O2S2) has been determined at five different temperatures, i.e. room temperature (293), 223, 173, 123 and 93 K. The solid-state work is complemented by the results of theoretical calculations of energies, geometries, difference electron densities and atomic charges of the free molecule. Analysis revealed static disorder caused by a higher energy conformer of the title compound, probably contaminating the crystal during its growth. The results support the contention that the electrical properties are mainly governed by the carbon backbone.

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Section: Introductionmentioning

confidence: 67%

Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal

Blockhuys¹,

Velde²,

Maes³

et al. 2003

Acta Crystallogr Sect B

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TheVilsmeier Reaction of Fully Conjugated Carbocycles and Heterocycles

Jones

Stanforth

1996

Organic Reactions

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In 1925 Fischer, Müller, and Vilsmeier published a paper describing the reaction between phosphoryl chloride and N ‐methylacetanilide, giving a number of products, including the quinolinium salt and another salt. The probable course of the reaction was given in a paper by Vilsmeier and Haack in 1927, and they made the important discovery that the reagent obtained from N ‐methylformanilide and phosphoryl chloride, represented as a salt, would react with N,N ‐dimethylaniline, giving 4‐ N,N ‐dimethylaminobenzaldehyde. No 2‐substituted products were observed in this reaction. Other N,N ‐dialkylaniline derivatives, including 3, N,N ‐trimethylaniline and 1‐ N,N ‐dimethylaminonaphthalene were also successfully used as substrates to prepare aromatic aldehyde derivatives. The gradual development of the reagent for synthesis was accompanied by interest in the nature of the reagent. It was discovered that other acid chlorides (e.g., thionyl chloride, carbonyl chloride, and oxalyl chloride) could be used in the reaction and that substituted amides other than formamides gave ketones, although in generally poorer yields. Thionyl chloride frequently gives sulfur‐containing products. The most commonly used amide is dimethylformamide (DMF) and there is now a consensus that the reagent formed from DMF and most acid chlorides, other than phosphoryl chloride, can be represented by the structure given in the chapter, and this is illustrated for the reaction between DMF and carbonyl chloride. The salt is a stable compound and is often isolated before being reacted with a substrate. It seems likely that the most commonly used reagent, that made from DMF and phosphoryl chloride, is an equilibrium mixture of iminium salts. Recent unpublished spectroscopic studies have indicated that in DMF solution there is an equilibrium mixture of iminium compounds. One of the electrophilic chloroiminium salts then reacts with a substrate in an electrophilic substitution process yielding an iminium salt, which is usually hydrolyzed to the aromatic aldehyde. Vinylogous chloroiminium salts can be prepared from the corresponding vinylogous formamide derivatives and these yield, after hydrolysis, α,β‐unsaturated products. This particular reaction is generally limited to more reactive substrates. The formation of carbon–carbon bonds to fully conjugated carbocycles and heterocycles is the subject of this chapter; a subsequent chapter considers carbon–carbon bond‐formation reactions in alkenes (including heterosubstituted alkenes such as enamines and enol ethers), alkynes, and activated methyl and methylene compounds (aldehydes, ketones, carboxylic acid derivatives, and nitriles). It is not surprising that the Vilsmeier reaction has been the subject of many review articles of varying scope and length. With so many excellent reviews dealing with the Vilsmeier reaction, its mechanism, and the structure of the various electrophilic reagents, coverage is restricted to important concepts rather than reiterate all the literature material. A brief description of the mechanism and regiochemistry of the Vilsmeier reaction is presented and this is elaborated with appropriate cases that deal with specific compound types.

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The Vilsmeier Reaction of Non‐Aromatic Compounds

Jones

Stanforth

2000

Organic Reactions

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This chapter extends the discussion to reactions between the Vilsmeier‐Haack reagent (subsequently referred to as the Vilsmeier reagent for brevity) and any other compounds in which a carbon‐carbon bond is formed. The discussion thus excludes reactions in which the Vilsmeier reagent acts as a chlorinating agent (for example in the preparation of acid chlorides), or in which it forms carbon‐oxygen or carbon‐nitrogen bonds, unless these are accompanied by formation of a carbon‐carbon bond. For a discussion of the nature of the reagent and of the mechanism of the reaction, the earlier chapter in vol. 49 should be consulted. There are also a number of reviews that deal at length with mechanisms of reactions involving the Vilsmeier reagent, notably those by Jutz and Marson, and hence this chapter will concentrate on applications, with brief mention of mechanisms when necessary. Wizinger has pointed out that alkenes could react with the Vilsmeier reagent, but his only examples were styrenes where the intermediate carbocation has considerable stability. Hydrolysis gives the cinnamaldehyde. In principle, any alkene which is not too sterically hindered can undergo this reaction, but the Vilsmeier reagent has low reactivity as an electrophile, and in practice activation is often necessary. The addition depends on the HOMO of the alkene, and anything increasing the HOMO energy will aid reaction, as for example further conjugation (dienes, trienes, etc.) or the presence of an electron‐donating substituent. Hence aldehydes and ketones are active in their enol forms, and enol ethers and enamines are good substrates. Indeed, all additions covered by this chapter can be regarded as alkene additions, even those on active methyl groups attached to electron‐deficient rings. As with any reaction involving carbocation intermediates, rearrangements are possible; the initial products are sometimes enamines, and this can give rise to polysubstitution. The substrates are grouped into eleven major subsections; references to reviews of particular relevance will be found in the appropriate subsection.

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Vilsmeier Formylation of 4-Dimethylaminostilbene

Cited by 8 publications

References 0 publications

Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal

Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal

TheVilsmeier Reaction of Fully Conjugated Carbocycles and Heterocycles

The Vilsmeier Reaction of Non‐Aromatic Compounds

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