Umsetzungen mit Monohydrazonen von Dicarbonylverbindungen, VI: Synthesen von 4‐Oxocarbonsäuren und deren Estern mit Hilfe von α‐Hydrazonoaldehyden

Abstract

a-Hydrazonoaldehyde (11) sind aus Ketonhydrazonen 14 durch Selendioxid-Oxidation oder durch Kupplung von Enaminen 12 rnit Diazoniumsalzen 13 darstellbar. Mit (Ethoxycarbonyl-methy1en)triphenylphosphoran (15) oder rnit Estern 17 in Gegenwart von Basen lassen sich a-Hydrazonoaldehyde 8, l l zu Hydrazonen ungesattigter 4-Oxocarbonester (16) umsetzen. Durch Hydrolyse oder reduktive Hydrolyse erhalt man ungesattigte bzw. gesattigte 4-Oxocarbonester (18 bzw. 19). Hydrazonoethyliden-Derivate von Ketonen ergeben bei der Hydrolyse 4-0x0carbonsauren (28 + 29). Reactions with Monohydrazones of Dicarbonyl Compounds, VI') Syntheses of 4-Oxocarboxylic Acids and their Esters by Means of a-Hydrazonoaldehydesa-Hydrazonoaldehydes (11) can be prepared by oxidation of ketone hydrazones 14 with selenium dioxide or by coupling of enamines 12 with a diazonium salt 13. The a-hydrazonoaldehydes 8, 11 react with (ethoxycarbony1methylene)triphenylphosphorane (15) or with carboxylic acid esters 17 in the presence of a base to give hydrazones of unsaturated 4-oxocarboxylic acid esters (16). By hydrolytic cleavage or by reductive hydrolysis unsaturated or saturated 4-oxocarboxylic acid esters (18 and 19, resp.) are obtained. Hydrolysis of hydrazonoethylidene derivatives of ketones leads to the formation of 4-oxocarboxylic acids (28 + 29).Zahlreiche Naturstoffe enthalten 5-Ring-Lactone als charakteristisches Strukturelement. Man findet einfache Lactone auch als Bestandteile naturlicher und synthetischer Aromen '). Das anhaltende Interesse an neuen Synthesewegen ist in der Literatur dokumentiert 3 -2 1 ) . Aus 4-Oxocarbonsauren lassen sich leicht ungesattigte 2 2 ) oder nach Reduktion der Ketofunktion gesattigte Lactone darstellen 23). Wir haben diese Oxosauren rnit Hilfe von a-Hydrazonoaldehyden dargestellt.Auf Grund dieser Ergebnisse konnte man erwarten, daD mit Estern als CH-aciden Komponenten gesattigte und ungesiittigte 4-Ketoester darstellbar sein wurden. Die Brauchbarkeit dieses Verfahrens hangt wesentlich von der Zuganglichkeit der a-Hydrazonoaldehyde ab. Wir haben daher zunachst verschiedene Synthesewege gepriift.Monohydrazone des Glyoxals (z. B. 8) sind aus Glyoxal und verschiedenen Hydrazinen darstellbar. Verwendet man den Dialdehyd im Uberschul3, so kann man die Bildung von Bishydrazonen weitgehend vermeiden ", '@. Im Methylglyoxal reagiert zunachst bevorzugt die Aldehydgruppe. Wir haben 11 a uber das Methylglyoxal-dimethylacetal erhalten 24). Eine Ubertragung dieser Reaktionsfolge auf hohere Homologe ist jedoch relativ aufwendig. l o ) M . Bielefeld und P . Kurath, J. Org. Chem. 34, 237 (1969).

Preparation of Imino Lactones by Electrophilic Cyclization of β,γ‐Unsaturated Hydroxamates: Formation of 3‐Cyanoprop‐2‐en‐1‐ones through Fragmentation Reactions

“…The reactivities of compound 47 and its E isomer have been briefly reported on in the literature. [11,15] In addition, we found that Michael additions were observed in good yields with soft carbanions formed from dimethyl malonate, β-keto ester and methyl (phenylsulfonyl)acetate (Scheme 6). The regiospecificities of these additions were deduced from the NMR spectra of the compounds and were consistent with previously published results.…”

“…The regiospecificities of these additions were deduced from the NMR spectra of the compounds and were consistent with previously published results. [11,15] With butyllithium, addition at the ketone function of 47 was observed and alcohol 51 was obtained. With other lithium derivatives (MeLi, tBuLi) and with Grignard reagents, complex reaction mixtures were observed [formation of alcohols and (or) Scheme 6.…”

“…The hydroxamates 56 and 57 were prepared as shown in Scheme 7 by hydroxy amidation and acylation of the corresponding known acids. Their reactions with bis(collidine)bromine(I) hexafluorophosphate led to the formation of the corresponding unstable cyclic imidates, which could not be purified by liquid chromatography over silica gel, so the crude reaction products were treated with triethylamine to lead to the formation of compounds 58 [15] and 59. [16] The structures of these compounds were determined from their NMR and IR spectra and by comparison with those reported in the literature.…”

“…138°C); see also ref. [15] (Z)-2-[3,4-Dihydro-1-oxonaphthalen-2(1H)-ylidene]acetonitrile (59): This compound was prepared by the procedure reported for the preparation of compound 47 (120 mg, 74 %). White solid, m.p.…”

“…After purification by liquid chromatography over silica gel only two products were isolated: the cyclic bromo imidate 7 (73 mg) and the unsaturated cyclic imidate 8 (33 mg). (6) [15] (0.66 mmol, 307 mg) was added to a toluene solution (10 mL) of hydroxamate 4 (127 mg, 0.6 mmol), cooled to -20°C. After 2 h at -20°C, the solution was allowed to warm to room temp.…”