Side‐Chain Retention During Lithiation of 4‐Picoline and 3,4‐Lutidine: Easy Access to Molecular Diversity in Pyridine Series

Kaminski, Thomas W.; Fort, Yves

doi:10.1002/ejoc.200300243

Cited by 34 publications

(24 citation statements)

References 19 publications

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“…Accordingly, its 4-methyl substituted sulfoxide derivative 5b was best prepared by selective lithiation of 4-picoline in the presence of 2-(dimethylamino)ethanol at 0°C. This was followed by treatment with diethyl disulfide at -78°C to afford 4-methyl-2-(ethylmercapto)pyridine [9] and, finally, sulfide-to-sulfoxide conversion using the same procedure involving magnesium monoperoxyphthalate reagent.…”

Section: Preparation Of Tridentate Ligandsmentioning

confidence: 99%

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO₂ Solar Cells with a High Solar‐Energy‐Conversion Efficiency

Chen

Liu

Wang

et al. 2007

Adv Funct Materials

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A new type of ruthenium complexes 6–8 with tridentate bipyridine–pyrazolate ancillary ligands has been synthesized in an attempt to elongate the π‐conjugated system as well as to increase the optical extinction coefficient, possible dye uptake on TiO2, and photostability. Structural characterization, photophysical studies, and corresponding theoretical approaches have been made to ensure their fundamental basis. As for dye‐sensitized solar cell applications, it was found that 6–8 possess a larger dye uptake of 2.4 × 10–7 mol cm–2, 1.5 × 10–7 mol cm–2, and 1.3 × 10–7 mol cm–2, respectively, on TiO2 than that of the commercial N3 dye (1.1 × 10–7 mol cm–2). Compound 8 works as a highly efficient photosensitizer for the dye‐sensitized nanocrystalline TiO2 solar cell, producing a 5.65 % solar‐light‐to‐electricity conversion efficiency (compare with 6.01 % for N3 in this study), a short‐circuit current density of 15.6 mA cm–2, an open‐circuit photovoltage of 0.64 V, and a fill factor of 0.57 under standard AM 1.5 irradiation (100 mW cm–2). These, in combination with its superior thermal and light‐soaking stability, lead to the conclusion that the concomitant tridentate binding properties offered by the bipyridine‐pyrazolate ligand render a more stable complexation, such that extended life spans of DSSCs may be expected.

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Section: Preparation Of Tridentate Ligandsmentioning

confidence: 99%

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO₂ Solar Cells with a High Solar‐Energy‐Conversion Efficiency

Chen

Liu

Wang

et al. 2007

Adv Funct Materials

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“…The use of the combination of n-butyllithium and lithium diethylamino ethoxyde (LiDMAE) has shown to be a "superbase" able to efficiently deprotonate the C-2 of pyridines by increasing the basicity and nucleophilicity of the alkylithium reagent. 81 Thus, recent applications of the use of this lithiating combination on 4-picoline and 3,4-lutidine, 82 4-(1-pyrrolyl)pyridine, 83 (S)-nicotine, 84 anisylpiridines 85 and 3-methylthiopyridine were reported. 86 A new related "superbase" has been developed by combining [(trimethylsilyl]methyl)lithium (TMSCH 2 Li) and LiDMAE, and it has found efficient application for the C-2 lithiation of sensitive chloro-and fluoropyridines.…”

Section: Aromatic Six-membered Ringsmentioning

confidence: 99%

Metalated Heterocycles in Organic Synthesis: Recent Applications

2007

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“…Metalated oxazoles, indoles, or furans can, however, be unstable and undergo ring-opening reactions [179,181,388]. Pyridines and other six-membered, nitrogen-containing heterocycles can also be lithiated [59,370,[390][391][392][393][394][395][396][397][398] or magnesiated [399], but because nucleophilic organometallic compounds readily add to electron-deficient heteroarenes, dimerization can occur, and alkylations of such metalated heteroarenes often require careful optimization of the reaction conditions [368,400,401] (Schemes 5.42 and 5.69). 176 Scheme 5.41.…”

Section: Aromatic Carbanionsmentioning

confidence: 99%

“…Electrophiles with a high tendency to act as single-electron oxidants are alkyl, allyl, and benzyl iodides and bromides, benzophenone, nitro compounds, and electron-poor aldehydes [233,507]. Dimerization of organolithium compounds and imidazolones [401,508,511,515]. Non-resonance-stabilized carbanions, such as metalated formamidines [233] (Scheme 5.25) or metalated benzyl alcohols [256], can also act as reducing agents.…”

Section: 46mentioning

confidence: 99%

The Alkylation of Carbanions

Dörwald

2004

Side Reactions in Organic Synthesis

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The deprotonation of organic compounds by strong, non-nucleophilic bases followed by C-alkylation with a suitable electrophile has become one of the most predictable and straightforward methods for formation of C-C bonds. The popularity of this chemistry is also a consequence of the often-seen close resemblance of feasible structural modifications by a deprotonation/alkylation strategy to an unsophisticated retrosynthetic analysis of a given target compound. Other reactions, which involve, for instance, substantial rearrangement of the carbon framework (e.g. Cope rearrangement, fragmentations, ring contractions or enlargements) are usually more difficult to take into account during retrosynthetic analysis.LDA and related, sterically hindered, lithium dialkylamides, first investigated by Levine [1], have completely replaced the more nucleophilic sodium amide, which had been the base of choice for many years [2]. Because the reactivity of an organometallic compound depends to a large extent on its state of aggregation (i.e. on the solvent and on additives) and on the metal, transmetalation of the lithiated intermediates and the choice of different solvents and additives emerged as powerful strategies for fine-tuning the reactivity of these valuable nucleophiles.In this chapter the alkylation of carbanions with simple carbon electrophiles will be discussed, with special emphasis on the structure-reactivity relationship of the carbanion and on side reactions. In this context the term "carbanion" refers to an intermediate prepared by in-situ deprotonation of an organic compound, followed by optional cation exchange (transmetalation), which tends to be alkylated at carbon by soft electrophiles such as MeI or PhCHO. This type of reactivity is characteristic of enolates with an ionic M-O bond or for organometallic compounds with a strongly polarized or ionic M-C bond, M typically being an alkali metal, Mg, Cu, or Zn. Carbanions can, alternatively, also be prepared by halogen-metal exchange [3-8], sulfoxide-or sulfone-metal exchange [9-13], or by transmetalation of stannanes. The most suitable reagents for performing such metalating exchange reactions are organometallic compounds with a metal-bound secondary or tertiary alkyl group, such as tBuLi, sBuLi, iPr 2 Zn [14, 15], or iPrMgHal [6]. These reagents are thermodynamically less stable than organometallic compounds with primary alkyl 5 146 Scheme 5.1. Approximate relative rates of proton transfer in water at thermoneutrality (DpK a = 0) [35, 39, 51]. 147 Scheme 5.2. The effect of fluorine on the acidity of organic compounds [24, 62-65]. 148 Scheme 5.3. Dependence of the reactivity of carbanions on their basicity [68, 72-74]. Regioselectivity of Deprotonations and AlkylationsThe organic chemist is occasionally confronted with the problem that a compound has several differrent X-H groups of similar pK a . If only one of these is to be alkylated, one option would be to perform a regioselective deprotonation. This can sometimes be achieved by exploiting small differences be...

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Side‐Chain Retention During Lithiation of 4‐Picoline and 3,4‐Lutidine: Easy Access to Molecular Diversity in Pyridine Series

Cited by 34 publications

References 19 publications

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO₂ Solar Cells with a High Solar‐Energy‐Conversion Efficiency

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO₂ Solar Cells with a High Solar‐Energy‐Conversion Efficiency

Metalated Heterocycles in Organic Synthesis: Recent Applications

The Alkylation of Carbanions

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Side‐Chain Retention During Lithiation of 4‐Picoline and 3,4‐Lutidine: Easy Access to Molecular Diversity in Pyridine Series

Cited by 34 publications

References 19 publications

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO2 Solar Cells with a High Solar‐Energy‐Conversion Efficiency

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO2 Solar Cells with a High Solar‐Energy‐Conversion Efficiency

Metalated Heterocycles in Organic Synthesis: Recent Applications

The Alkylation of Carbanions

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Product

Resources

About

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO₂ Solar Cells with a High Solar‐Energy‐Conversion Efficiency

New Family of Ruthenium‐Dye‐ Sensitized Nanocrystalline TiO₂ Solar Cells with a High Solar‐Energy‐Conversion Efficiency