Dibenzofuran. XVI. The Two-Stage Metalation of 2-Bromodibenzofuran<sup>1</sup>

Gilman, Henry; Langham, W.H.; Willis, H. B.

doi:10.1021/ja01859a033

Cited by 26 publications

(11 citation statements)

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“…Treatment of 4-bromoanisole with butyl lithium followed by reaction of the mixture with a diaryl ketone gave dye bases containing bromine by-product. This type of by-product formation did not take place in the case of 2-and 3-bromoanisoles [12]. It is possible to minimize such interfering side reactions by using the more reactive complex formed between butyl lithium and bis-1,2-dimethylaminoethane [9] and also employing shorter reaction periods.…”

Section: Methods B (Transmetallation)mentioning

confidence: 99%

Synthesis and electronic absorption spectra of some novel methoxy half-analogs of Malachite Green and Brilliant Green

Saadatjou

Hallas

2008

Fibers Polym

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In this work, various series of triarylmethane dyes containing one or more terminal methoxy substituent together with a variable tertiary amino group have been synthesized. The effects of electron-donating and electron-withdrawing groups have been systematically examined and electron absorption spectra of dyes determined. The absorption bands of the methoxy half-analogues of Malachite Green and Brilliant Green show pronounced hypsochromic shifts together with reduction in intensity owing to the inherent electronic asymmetry of the system. The corresponding dye bases are incompletely ionized in acid solution. Julolidine and Kairoline analogues of these dyes produce further hypsochromic shifts of both visible absorption bands in accordance with enhanced conjugation of the terminally bridged substituents. Crowding substituents at the central carbon atom in the series of methoxy half-analogues produce hypsochromic shifts of the absorption bands owing to the inherent electronic asymmetry; bond order alteration throughout the system ensures that crowding effects are minimized by rotation about essential single bonds.

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Section: Methods B (Transmetallation)mentioning

confidence: 99%

Synthesis and electronic absorption spectra of some novel methoxy half-analogs of Malachite Green and Brilliant Green

Saadatjou

Hallas

2008

Fibers Polym

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“…For example, lithiation of 2-bromodibenzofuran (11) with n-BuLi initially undergoes halogen-metal exchange to give 2-lithiodibenzofuran (12), which then lithiates unreacted 2-bromodibenzofuran to give 2-bromo-4-lithiodibenzofuran (13) along with dibenzofuran (14; Scheme 4), as inferred from the structure of the carboxylation product obtained. 22,23 Despite the electronegativity of oxygen and nitrogen atoms, lithiation at a carbon atom attached to an NMe 2 or OMe group is disfavored as a result of the destabilizing interaction of the lone pairs of electrons on N or O with the electrons of the C-Li bond (Figure 3). However, such α-lithiation may be favored when the lone pairs are delocalized by conjugation with a carbonyl group, which reduces the repulsive interaction and provides an attractive interaction between the Li and O atoms ( Figure 3).…”

Section: Figurementioning

confidence: 99%

Unravelling Factors Affecting Directed Lithiation of Acylaminoaromatics

2018

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Ureas, pivalamides, and carbamates are widely used as directing metalation groups (DMGs) due to their good directing ability, low cost, ease of access, and ease of removal. Lithiation of substituted benzenes having such directing metalation groups using various alkyllithiums in anhydrous solvent at low temperature provides the corresponding lithium intermediates, but lithiation may take place at various sites. Reactions of the lithium reagents obtained in situ with various electrophiles give the corresponding derivatives, typically substituted at the site(s) where initial lithiation occurred, often in high yields. However, it is often difficult to predict what reagents and/or conditions might be needed to give specific products or to draw general conclusions about the factors that influence the reactions, especially when the reagents, temperature, and solvents used in reported reactions are not directly comparable. In this review, therefore, we attempt to unravel the various factors that influence the lithiation of various simple aromatic compounds containing urea, pivalamide, and carbamate groups.1 Introduction2 Lithiation with DMG Attached Directly to the Phenyl Ring2.1 Influence of the DMG2.2 Influence of Substitution on the Phenyl Ring3 Lithiation with the DMG Separated by a CH2 Group from the Phenyl Ring3.1 Effect of the DMG3.2 Influence of Substitution on the Phenyl Ring4 Lithiation with the Phenyl Ring and DMG Separated by Two or More CH2 Groups4.1 Effect of the DMG and Its Distance from the Phenyl Group4.2 Effect of Substituents on the Phenyl Ring5 Conclusions

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“…Then 2.3 g of p-methoxybenzoic acid was obtained and the yield was 94%, mp 183 -184 8C [lit. 18 184 8C].…”

Section: Typical Proceduresmentioning

confidence: 99%