Ring enlargement reactions of tetramic acid derivatives

Poschenrieder, Hermann; Eckl, E.; Stachel, Hans‐Dietrich; Windt, Andreas; Polborn, Kurt

doi:10.1002/jhet.5570370428

Cited by 9 publications

(4 citation statements)

References 25 publications

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“…Exposure of epoxide 59 to BF 3 results in C–C bond cleavage to the corresponding aldehyde and 2-keto-3-hydroxy derivative. The use of BF 3 or other Lewis acids in the ring-expansion process was not assessed. , …”

Section: Reaction Of Ketones With Aryldiazomethanesmentioning

confidence: 86%

Homologation Reaction of Ketones with Diazo Compounds

2016

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This review covers the addition of diazo compounds to ketones to afford homologated ketones, either in the presence or in the absence of promoters or catalysts. Reactions with diazoalkanes, aryldiazomethanes, trimethylsilyldiazomethane, α-diazo esters, and disubstituted diazo compounds are covered, commenting on the complex regiochemistry of the reaction and the nature of the catalysts and promoters. The recent reports on the enantioselective version of ketone homologation reactions are gathered in one section, followed by reports on the use of cyclic ketones ring expansion in total synthesis. Although the first reports of this reaction appeared in the literature almost one century ago, the recent achievements, in particular, for the asymmetric version, forecast the development of new breakthroughs in the synthetically valuable field of diazo chemistry.

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Section: Reaction Of Ketones With Aryldiazomethanesmentioning

confidence: 86%

Homologation Reaction of Ketones with Diazo Compounds

2016

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“…Electron withdrawing substituents will stabilize a different dipolar intermediate, in which elimination of aryl isocyanate will favourably compete with the carbon-sulphur scission thus leading to a thiophene derivative. Acid promoted rearrangement give dihydroxy pyridones in reasonable yield [84]. With excess diazomethane and prolonged reaction time, the bicyclopropanes are formed in good yield.…”

Section: From Other Aromatic Heterocyclic Ringsmentioning

confidence: 97%

New Synthetic Methods to 2-Pyridone Rings

Torres¹,

Gil²,

Parra

2005

COC

203

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The synthesis of a substituted 2-pyridone ring is a topical area of continuing interest due to the number of biologically active molecules containing this moiety. Over the last decade, natural compounds with this structure have emerged as potent antitumor antiviral and attention, because those compounds may be studied as a simple model for investigating mechanisms of some enzymatic reactions or for discerning the behavior of nucleic acids bases in connection with mutation due to base mispairing or other mistaken helices. Recent studies have shown the usefulness of 2-pyridones as intermolecular connectors between building blocks in material science. Thus, despite the large number of methods known for their synthesis, new procedures are continuously being developed. Two main synthetic approaches can be found in the literature: from other heterocycles systems or condensation of acyclic systems. The latter can be further classified depending on the bond formed in the cyclization step: by C-C or C-N bond generation. The latter can be subclassified depending on the first condensation step. This is a review of new or improved methods for constructing 2-pyridone rings. This article will be restricted to ring formation, which can be included in the total synthesis of several compounds with specific biological or material properties.The pursuit of these properties requires efficient synthetic routes that allow rapid assembly and variation of multiple pendant substituents on the heteroaromatic case, which permits rapid analogsynthesis (RAS) [1].

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“…When treated with diazomethane in excess, the enol ethers 3a -c were converted into the bicyclic imides 8a -c by N-methylation and subsequent cyclopropanation. The imides 8a,b and their use for the synthesis of functionalized pyridinones by ring expansion have recently been described by us [16]. In this context we were interested to synthesize sulfonimides as heteroanalogs of the imides 3a and 8a.…”

mentioning

confidence: 99%

“…-Ozonation of the lactams 1 in nonparticipating solvents furnished the maleimides 3a -c (Scheme 1). Maleimides 3a and 3b have been synthesized previously on another route [16]. The lactams 1a -c contain conjugated exocyclic and endocyclic C=C bonds.…”

mentioning

confidence: 99%

Functionalized Imides by Regioselective Ozonation

Poschenrieder¹,

Stachel²,

Eckl³

et al. 2006

Helvetica Chimica Acta

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Ozonations of alkoxy-and (acyloxy)-substituted alkylidene-lactams 1 and 5 or of the alkylidene-sultams 9 and 10 proceeded by regioselective cleavage of the exocyclic C=C bonds (Schemes 1 and 2). These bonds are part of an enamide system and, therefore, possess considerable polarity as shown by 13 C-NMR spectra. As a result, the partly known maleimides 3 and 6 or the sulfonimides 11 were obtained. Compounds 3 and 11 reacted with diazomethane to give the highly reactive bicyclic derivatives 8 and 12, respectively. The cinnamylidene-lactames 16a,b were converted by selective ozonolysis mainly into the formylmethylene lactames 17a,b (Scheme 3). The amino-substituted aldehyde 20 bears a structural relationship to the lactone antibiotic basidalin 21a. The tendency of some donor-substituted maleimides to undergo [2 + 2] cycloadditions was assessed (Scheme 4). The configuration of the photodimers 22a,b and 24a,b was established by X-ray crystallography.Introduction. -The cleavage of alkene C=C bonds by ozone to give aldehydes, ketones, and carboxylic acids was introduced into organic chemistry at the beginning of the 20 th century by Harries [1]. Ozonolyses take place under extremely mild reaction conditions and often with excellent yields. The individual course of an ozonization, however, is strongly dependent on the constitution of the starting material, the solvent, and the choice of reductive or oxidative workup conditions (for a comprehensive review, see [2]).A basic three-step mechanism was formulated by Criegee and is now bearing his name [3]. In a sequence of concerted 1,3-dipolar cycloaddition and cycloreversion, carbonyl oxides [4] are formed which are captured by internally generated carbonyl compounds in another 1,3-dipolar cycloaddition to yield ozonides. As a result, for unsymmetrical alkenes, substituent rules for the regioselective OÀO splitting in the cycloreversion step have been formulated [5] [6]. There are, however, exceptions from these rules, and the ozonide-forming step may be bypassed due to low dipolarophilicity of the carbonyl intermediate. Both is examplified in the ozonolysis of ketene acetals [7]. Modifications of the original Criegee mechanism have been introduced later [8]. An alternative mechanistic concept of ozonations was recently brought up for discussion [9]. According to the donor-acceptor concept, ozonations are regarded as oxidation reactions with radical-ion intermediates.It is well known that the C=C bond of enol ethers is readily cleaved by ozone forming a carbonyl compound and a carboxylic acid ester [10 -14]. Analogously, in the ozonolysis of enol esters, beside a carbonyl compound, a mixed carboxylic acid anhydride is

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Ring enlargement reactions of tetramic acid derivatives

Cited by 9 publications

References 25 publications

Homologation Reaction of Ketones with Diazo Compounds

Homologation Reaction of Ketones with Diazo Compounds

New Synthetic Methods to 2-Pyridone Rings

Functionalized Imides by Regioselective Ozonation

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