Nachträge zu den „Synthesen mit Diazo‐methan”︁

Arndt, F.; Eistert, Bernd; Amende, J.

doi:10.1002/cber.19280610864

Cited by 35 publications

(4 citation statements)

References 13 publications

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“…With diazoacetone, azine 9a contains different substituents at reactive carbonyl groups, which leads to a mixture of pyridazines 11 and 12 in the ratio ~2.6 : 1. The isomers were assigned from the 1 H and 13 C NMR chemical shifts of the signals for the methyl groups: δ H 2.1-2.2 and δ C 15-16 for MeC (5) and δ H 2.6-2.9 and δ C 25-27 for MeCOC (3). It should also be noted that each of the pyridazines 10-12, like pyridazines 3 and 4, exists in solution in the ketone and enol forms: their 1 H and 13 C NMR spectra show charac teristic signals for the methylene and olefinic protons (see Table 1).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of tetrasubstituted pyridazines via cascade reactions of diazocarbonyl compounds with pyridinium ylides

et al. 2008

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Reactions of pyridinium ylides with diazocarbonyl compounds involve the formation of functionalized azine intermediates that can undergo intramolecular cyclocondensation into tetrasubstituted pyridazines provided the starting reagents contain carbonyl groups. Reactions of pyridinium ylides with diazo compounds were studied for various substituents in both the substrates.Pyridinium and triphenylphosphonium ylides con taining a carbonyl or carboxyl group at the ylide C atom react with diazo esters to give polysubstituted pyrazoles or pyridazines. 1,2 Such reactions are of cascade character and involve sequential interactions of two molecules of phosphorus ylide (or three molecules of nitrogen ylide) with a molecule of diazo ester with simultaneous elimination of the ylide forming molecule. 3 For pyridinium ylides 1 containing a carboxyl or carbonyl group, these processes usually differ in the final step, namely, heterocyclization (Scheme 1). In the case of an azine containing four ester groups, cyclization leads, through the corresponding ene hydrazone, 1 to tetrahydropyridazinetetracarboxylate 2; for an azine containing a conjugated carbonyl group, cyclization gives tetrasubstituted pyridazine 3 via aldol condensation. 3 In both cases, the overall "one pot" pro cess results in the formation of one C-N bond and three new carbon-carbon bonds. Results and DiscussionAs noted above, reactions of pyridinium ylides con taining a carbonyl or carboxyl group at the ylide C atom have been investigated only with diazo esters. To extend the scope of this reaction and obtain new heterocyclic compounds, here we studied a reaction of pyridinium benzoylmethylide with methyl diazoacetate and, for the first time, reactions of carbonyl and methoxycarbon yl containing pyridinium ylides with diazo ketones.In contrast to ylides 1a,b, pyridinium benzoylmeth ylide (1c) is stable under normal conditions 4 and thus can be both used in the individual state and generated from appropriate pyridinium salts under the action of bases. It turned out that ylide 1c reacts with methyl diazoacetate like ylide 1b, regardless of the way of its preparation (use of a specially prepared ylide for the reaction in CH 2 Cl 2 or in situ generation of the ylide from phenacylpyridini um bromide and K 2 CO 3 in acetonitrile). A series of cas cade transformations give substituted pyridazine 4 in 64-71% yield (Scheme 2). Essentially, a diazo acetate molecule adds through its terminal N atom to the ylide molecule with elimination of pyridine and formation of a reactive azine. Then two more ylide molecules add sequentially to the azine with elimination of two pyridine molecules. The final step of the process involves aldol cyclocondensation of tetrasubstituted azine 5 into py ridazine 4.As in the case of methylpyridazine 3, phenylpyridazine 4 exists in solution in the ketone and enol forms. Accord Scheme 1

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Section: Resultsmentioning

confidence: 99%

Synthesis of tetrasubstituted pyridazines via cascade reactions of diazocarbonyl compounds with pyridinium ylides

et al. 2008

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“…A high number of procedures suitable for the preparation of α-amino diazoketones from N -Fmoc-protected natural α-amino acids have already been published. The most common route is represented by the Arndt–Eistert step realized starting from differently carboxy-activated N -protected α-amino acids. , In this context, the acylation of diazoalkanes using acid chlorides and fluorides, , or less commonly acid anhydrides, , are familiar approaches for the synthesis of α-amino diazoketones. Nevertheless, some practical problems of safety due to the use of fluorinating reagents are associated with the preparation of protected N -Fmoc-α-amino acid fluorides, while the corresponding chlorides cannot be prepared starting from α-amino acids containing acid-labile and the benzyloxycarbonyl (Z) groups.…”

Section: Introductionmentioning

confidence: 99%

A One-Pot Procedure for the Preparation ofN-9-Fluorenylmethyloxycarbonyl-α-amino Diazoketones from α-Amino Acids

et al. 2012

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The study describes a new "one-pot" route to the synthesis of N-9-fluorenylmethyloxycarbonyl (Fmoc) α-amino diazoketones. The procedure was tested on a series of commercially available free or side-chain protected α-amino acids employed as precursors. The conversion into the title compounds was achieved by masking and activating the α-amino acids with a single reagent, namely, 9-fluorenylmethyl chloroformate (Fmoc-Cl). The resulting N-protected mixed anhydrides were reacted with diazomethane to lead to the α-amino diazoketones, which were isolated by flash column chromatography in very good to excellent overall yields. The versatility of the procedure was verified on lipophilic α-amino acids and further demonstrated by the preparation of N-Fmoc-α-amino diazoketones also from α-amino acids containing side-chain masking groups, which are orthogonal to the Fmoc one. The results confirmed that tert-butyloxycarbonyl (Boc), tert-butyl ((t)Bu), and 2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl (Pbf), three acid-labile protecting groups mostly adopted in the solution and solid-phase peptide synthesis, are compatible to the adopted reaction conditions. In all cases, the formation of the corresponding C-methyl ester of the starting amino acid was not observed. Moreover, the proposed method respects the chirality of the starting α-amino acids. No racemization occurred when the procedure was applied to the synthesis of the respective N-Fmoc-protected α-amino diazoketones from L-isoleucine and L-threonine and to the preparation of a diastereomeric pair of N-Fmoc-protected dipeptidyl diazoketones.

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“…Dem Elutionsdiagramm (Abbild. 1) unseres Partialhydrolysates nach mul3te somit in den Abbauprodukten die Zahl der P-Lysinreste in der Reihenfolge SO, S1, SZ abnehmen.…”

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“…Die Farbintensitaten der R1und Rz-Zone verhielten sich etwa wie 7:1. R1 zeigte in funf Losungsmittelsystemen den gleichen R F -Wert wie Glucosamin.…”

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Geomycin IV.; Antibiotica aus Actinomyceten, XLII

Brockmann

Cölln

1959

Chem. Ber.

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BROCKMANN und COLLN Jahrg. 92 Cer Keto-trans-tetramethylester XZXg kristallisiert nach dem Urnlosen aus Methanol zuerst in farblosen feinen Nadeln, die nach kurzer Zeit in dimorphe prismatische Plattchen iibergehen. Er schmilzt bei 198-199" und gibt im Gemisch mit dem cis-Tetramethylester (entspr. V A) vom Schmp. 201 -202" eine starke Schmp.-Depression. C40H38010 (678.7) Ber. C 70.78 H 5.64 OCH3 22.86 Gef. C 70.70, 70.98 H 5.73, 5.65 OCH3 22.74, 23.01Die beiden Keto-trans-tetramethylester XIXa und p fallen etwa im Verhaltnis 1 : 1 an. b) 3 g cis-Tetramethylestrr entspr. V B vom Schmp. 222-223" werden wie oben rnit Na-Methylatlosung unter RiickfluB gekocht. Die Aufarbeitung und anschlieBende Veresterung liefert hier ebenfdls die beiden Keto-trans-tetramethylester X I X a und 8.

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Nachträge zu den „Synthesen mit Diazo‐methan”︁

Cited by 35 publications

References 13 publications

Synthesis of tetrasubstituted pyridazines via cascade reactions of diazocarbonyl compounds with pyridinium ylides

Synthesis of tetrasubstituted pyridazines via cascade reactions of diazocarbonyl compounds with pyridinium ylides

A One-Pot Procedure for the Preparation ofN-9-Fluorenylmethyloxycarbonyl-α-amino Diazoketones from α-Amino Acids

Geomycin IV.; Antibiotica aus Actinomyceten, XLII

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