Studies on Dimethylhyddrazones of Heteroaryl Aldehydes. The Reactivity of 2-Formylfuran, 2-Formylthiophene and 1-Methyl-2-formylpyrrole N,N-Dimethylhydrazones with Methyl Propiolate and Diethyl Azodicarboxylate

Abarca, Belén; Ballesteros, Rafaél; González, Eduvigis; Sancho, Patrícia; Sepúlveda, José; Soriano, Conxa

doi:10.3987/com-90-5477

Cited by 12 publications

(6 citation statements)

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“…[55] The addition of 96 to acetylenedicarboxylate 99 and to tetracyanoethylene 102 to afford 100 [56] and 101, [57] respectively, have also been documented, but the latter reaction may possibly proceed by an addition-elimination mechanism (Scheme 18). This course is remarkable, because both furan-2-carbaldehyde dimethylhydrazone 96 (X = O) as a good diene exemplified by the synthesis of 103 [58] and the three electrondeficient substrates as dienophiles are well-known partners in the Diels-Alder reaction.…”

Section: Nucleophilic Additions Of Vinylogous Azaenamines To Activatementioning

confidence: 99%

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

et al. 2007

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The isoelectronic replacement of the α‐carbon of enamines by nitrogen leads to the corresponding hydrazones, and thus, they can be termed “aza‐enamines”. Hence, aldehyde N,N‐dialkylhydrazones enable analogous electrophilic substitutions at the imine carbon that corresponds to the β‐carbon of enamines. In addition, after hydrolysis of the product hydrazones to the parent ketones or aldehydes, these reactions constitute an umpolung of the classical carbonyl reactivity and overall a nucleophilic acylation or formylation. This review covers the aza‐enamine chemistry from its very beginning in the late 1960s up to this year. In the first part, reactions of aromatic, aliphatic, and heterocyclic aldehyde N,N‐dialkylhydrazones with highly reactive substrates such as the Vilsmeier and Mannich reagents, sulfonyl isocyanates, perfluoroacetic anhydride, and inorganic electrophiles such as halogens and phosphorus tribromide are described. The hydrazones of α,β‐unsaturated aldehydes react as vinylogous aza‐enamines at the terminal carbon providing unsaturated aldehydes. As electron‐rich dienes and dienophiles, they also form Diels–Alder adducts and thus interesting N‐heterocycles. The second part covers carbon–carbon bond formations of the sterically less‐demanding formaldehyde N,N‐dialkylhydrazones with synthetically very useful electrophiles such as various Michael acceptors and carbonyl compounds. Formaldehyde SAMP‐hydrazone and related derivatives generally give excellent asymmetric inductions. Finally, first organocatalytic versions of the aza‐enamine chemistry are presented. In summary, the rich chemistry of aldehyde N,N‐dialkylhydrazones as neutral acyl anion, formyl anion, and cyanide equivalents is demonstrated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Section: Nucleophilic Additions Of Vinylogous Azaenamines To Activatementioning

confidence: 99%

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

et al. 2007

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“…However, in the case of hydrazones of aldehydes of π-excess five-membered heterocycles the trifluoroacetylation [20], and aminomethylation [21] reactions, and the interaction with electron-deficient unsaturated compounds [22][23][24], proceed regioselectively at position 5 of the ring, which is explained by __________________________________________________________________________________________…”

mentioning

confidence: 99%

“…One of the most promising groups, in our opinion, is the N,N-dimethylhydrazonomethyl group, which may readily be transformed into an aldehyde group [16], one of the most frequently used functional groups in organic synthesis [17]. At the same time the actual N,N-disubstituted hydrazonomethyl group is widely used in asymmetric synthesis [18,19] and is a reactive nucleophilic substrate, similar to enamines according to the azaenamine concept [18].However, in the case of hydrazones of aldehydes of π-excess five-membered heterocycles the trifluoroacetylation [20], and aminomethylation [21] reactions, and the interaction with electron-deficient unsaturated compounds [22][23][24], proceed regioselectively at position 5 of the ring, which is explained by __________________________________________________________________________________________ …”

mentioning

confidence: 99%

Interaction of N,N-dimethylhydrazonomethyl and α-hydroxyketone groups in hetaryl analogs of unsymmetrical benzoins

Ivonin

Lapandin

Штамбург

2005

Chem Heterocycl Compd

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The reaction of phenylglyoxal hydrate with N,N-dimethylhydrazones of furfural and 1-methylpyrrole-2-carbaldehyde proceeds regioselectively at position 5 of the heterocycle. The hetaryl analogs of α-benzoins obtained are quantitatively isomerized into the isomeric β-benzoins. The N,N-dimethylhydrazonomethyl group, while activating the hetaryl residue, reduces the time for isomerization compared with unfunctionalized benzoins. The N,N-dimethylhydrazonomethyl group is readily transformed into an aldehyde or nitrile group and enters into a trans-hydrazonation reaction.The chemical properties of benzoins studied up to the present time are overwhelmingly linked in the majority of cases with the transformation of the α-hydroxyketone group and with the effect of (het)aryl residues on its reactivity. Consequently the desired substituents required in the (het)aryl residues are usually introduced at the stage of obtaining the benzoin, for example, in various modifications of the benzoin condensations [1-7], hydroxyalkylation of arylglyoxals of electron-rich benzenes and π-excess heterocycles [8-10]. Among the chemical properties affecting (het)aryl residues two types are known: the formation of benzofurans on photolysis of desyl esters of carboxylic, carbamic, and phosphoric acids, which occurs through intramolecular [2+2] cycloaddition of the carbonyl group to the double bond of the electron-rich aryl residue [11][12][13][14], and electrophilic substitution directly into the (het)aryl residue: formylation of furoin [15], and excessive hydroxymethylation of a pyrrole ring with phenylglyoxal [10]. The effect of an α-hydroxyketone group on the reactivity of substituents in the (het)aryl residue of isomeric benzoins remains unstudied.It is interesting to study benzoins containing functional groups in the (het)aryl residues capable of further transformation within wide limits. One of the most promising groups, in our opinion, is the N,N-dimethylhydrazonomethyl group, which may readily be transformed into an aldehyde group [16], one of the most frequently used functional groups in organic synthesis [17]. At the same time the actual N,N-disubstituted hydrazonomethyl group is widely used in asymmetric synthesis [18,19] and is a reactive nucleophilic substrate, similar to enamines according to the azaenamine concept [18].However, in the case of hydrazones of aldehydes of π-excess five-membered heterocycles the trifluoroacetylation [20], and aminomethylation [21] reactions, and the interaction with electron-deficient unsaturated compounds [22][23][24], proceed regioselectively at position 5 of the ring, which is explained by __________________________________________________________________________________________

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“…The hetero-Diels-Alder reaction is a powerful tool for the creation of six-membered heterocycles [67]. Of the many dienes used in synthesis 1-azadienes constitute an important class of compounds, among which 1-aza-1,3-dienes with a C=C bond that is part of a heteroarene are of particular interest for the production of condensed heterocyclic systems [68,69]. An example of such a structure is the N,N-dimethylhydrazone of 1-ethoxycarbonyl-3-formylindole, which readily enters into [4+4] cycloaddition with such a electron-deficient dienophile as N-methylmaleimide [70].…”

mentioning

confidence: 99%

γ-Carbolines and their hydrogenated derivatives. 1. Aromatic γ-carbolines: methods of synthesis, chemical and biological properties (review)

Alekseyev

Kurkin

Yurovskaya

2009

Chem Heterocycl Comp

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Studies on Dimethylhyddrazones of Heteroaryl Aldehydes. The Reactivity of 2-Formylfuran, 2-Formylthiophene and 1-Methyl-2-formylpyrrole N,N-Dimethylhydrazones with Methyl Propiolate and Diethyl Azodicarboxylate

Cited by 12 publications

References 0 publications

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

Aldehyde N,N‐Dialkylhydrazones as Neutral Acyl Anion Equivalents: Umpolung of the Imine Reactivity

Interaction of N,N-dimethylhydrazonomethyl and α-hydroxyketone groups in hetaryl analogs of unsymmetrical benzoins

γ-Carbolines and their hydrogenated derivatives. 1. Aromatic γ-carbolines: methods of synthesis, chemical and biological properties (review)

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