Selective acylation of 2,4-lutidine at its 2- and 4-methyl group

Levine, Robert S.; Dimmig, Daniel A.; Kadunce, William M.

doi:10.1021/jo00940a007

Cited by 24 publications

(7 citation statements)

References 4 publications

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“…A1E was synthesized as shown in Scheme . Site-specific deprotonation , of 2,4-dimethylpyridine ( 7 ) with NaNH 2 in liquid ammonia, followed by addition of retinoidyl aldehyde 8 , led to alcohol 9 , which was subjected to acid-catalyzed elimination to give all-trans pyridyl retinoid 10 . Alkylation of 10 with 2-iodoethanol in nitromethane under reflux afforded the pyridinium substrate A1E ( 4 ).…”

Section: Resultsmentioning

confidence: 99%

Photochemistry of A1E, a Retinoid with a Conjugated Pyridinium Moiety: Competition between Pericyclic Photooxygenation and Pericyclization

et al. 2004

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The photochemistry of the retinoid analogue A1E shows an oxygen and solvent dependence. Irradiation of A1E with visible light (lambda(irr) = 425 nm) in methanol solutions resulted in pericyclization to form pyridinium terpenoids. Although the quantum yield for this cyclization is low (approximately 10(-4)), nevertheless the photochemical transformation occurs with quantitative chemical yield with remarkable chemoselectivity and diastereoselectivity. Conversely, irradiation of A1E under the same irradiation conditions in air-saturated carbon tetrachloride or deuterated chloroform produced a cyclic 5,8-peroxide as the major product. Deuterium solvent effects, experiments utilizing endoperoxide, phosphorescence, and chemiluminescence quenching studies strongly support the involvement of singlet oxygen in the endoperoxide formation. It is proposed that, upon irradiation, in the presence of oxygen, A1E acts as a sensitizer for generation of singlet oxygen from triplet oxygen present in the solution; the singlet oxygen produced reacts with A1E to produce cyclic peroxide. Thus, the photochemistry of A1E is characterized by two competing reactions, cyclization and peroxide formation. The dominant reaction is determined by the concentration of oxygen, the concentration of A1E, and the lifetime of singlet oxygen in the solvent employed. If the lifetime of singlet oxygen in a given solvent is long enough, then oxidation (peroxide formation) is the major reaction. If the singlet oxygen produced is quenched by the protonated solvent molecules faster than singlet oxygen reacts with A1E, then cyclization dominates.

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Section: Resultsmentioning

confidence: 99%

Photochemistry of A1E, a Retinoid with a Conjugated Pyridinium Moiety: Competition between Pericyclic Photooxygenation and Pericyclization

et al. 2004

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“…[42] Additionally, while only the methyl at C2 is attacked with phenyllithium, a mixture (~80 : 20, this time in favour of the C4 deprotometallation) was obtained by Levine and co-workers when testing a stronger base, phenylsodium, in benzene. [42] These studies tend to indicate that the coordination of the base metal by the pyridine nitrogen (Li > Na) promotes a first reaction on the methyl at C2. Under kinetic conditions (nonreversible reaction; for example in the case of n-BuLi [41] or when LiDA is used at À 78 °C [43] ), it is therefore the 2,4-lutidine αmetallated at C2 which is formed and then intercepted by the electrophile.…”

Section: On the Synthesis Of [(Linet 2 ) 4 • (Thf) X ]mentioning

confidence: 98%

Lateral Deprotometallation‐Trapping Reactions on Methylated Pyridines, Quinolines and Quinoxalines Using Lithium Diethylamide

et al. 2023

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The functionalization of methylated azines and diazines has aroused the interest of chemists given the structural diversity that it affords. Hindered lithium dialkylamides have been used to deprotometallate these substrates chemoselectively. In contrast, it can be observed that, despite some promising work, lithium diethylamide has been used very little for this purpose. Our objective here is on the one hand to make an inventory of what reagents have been used to deprotometallate methylpyridines, ‐quinolines and ‐quinoxalines, and on the other hand to describe the results obtained by seeking to functionalize a series of substrates with lithium diethylamide (picolines, 2,4‐lutidine, methylquinolines and 2‐methylquinoxaline). Our efforts to take advantage of the use of an in‐situ trap (a zinc chloride chelate) in these reactions are also described.

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“…The main feature of the reactivity of alkylquinolines is deprotonation of such alkyl moieties and reaction with electrophiles[215]. In this context, several 2-ketomethylquinolines have been synthesized by heating 2-methylquinolines with acyl chlorides in a conventional microwave oven and in the presence of silica gel (Scheme 17.86)[216].…”

mentioning

confidence: 99%

Six‐Membered Heterocycles: Quinoline and Isoquinoline

Alajarı́n

Burgos

2011

Modern Heterocyclic Chemistry

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Selective acylation of 2,4-lutidine at its 2- and 4-methyl group

Abstract: 2,4-Lutidine (1) has been acylated preferentially a t its 2-or 4-methyl group depending on the condensing agent.

Cited by 24 publications

References 4 publications

Photochemistry of A1E, a Retinoid with a Conjugated Pyridinium Moiety: Competition between Pericyclic Photooxygenation and Pericyclization

Photochemistry of A1E, a Retinoid with a Conjugated Pyridinium Moiety: Competition between Pericyclic Photooxygenation and Pericyclization

Lateral Deprotometallation‐Trapping Reactions on Methylated Pyridines, Quinolines and Quinoxalines Using Lithium Diethylamide

Six‐Membered Heterocycles: Quinoline and Isoquinoline

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