The Synthesis of the β‐Lactam Function

Koppel, G. A.

doi:10.1002/9780470187197.ch2

Chemistry of Heterocyclic Compounds: A Series of Monographs

1983

DOI: 10.1002/9780470187197.ch2

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The Synthesis of the β‐Lactam Function

G. A. Koppel¹

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Cited by 9 publications

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Stereochemical Aspects of a Two-Step Staudinger Reaction − Asymmetric Synthesis of Chiral Azetidine-2-ones

et al. 2000

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Reaction of N‐trialkylsilylimines with a variety of glycine‐derived ketenes produced 1,3‐azadienes, which in some cases have been isolated and characterised. A conrotatory ring closure of these compounds gave rise to the formation of the azetidine‐2‐ones, thus allowing a formal two‐step Staudinger reaction. Exclusive trans diastereoselectivity was observed. A less stringent diastereofacial selectivity was obtained. A set of experiments has been performed in order to evaluate the influence of the structural parameters as well as reaction conditions. Ab initio studies at MP2/6−31G* and QCISD(T)/6−311G** levels on model compounds provide a rationalization of the experimental results obtained. From the experimental as well as theoretical data it is clear that the presence of the silyl enol group in the intermediate azadiene is crucial in its stabilisation and plays a fundamental role in the conrotatory ring closure and, therefore, in the formation of the azetidine‐2‐one ring.

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Stereochemical Aspects of a Two-Step Staudinger Reaction − Asymmetric Synthesis of Chiral Azetidine-2-ones

et al. 2000

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Eine einfache Synthese von β‐Selenolactamen

1990

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Um die an der Elektrode ablaufenden Reaktionen aufzuklaren, wurden die Enole l a , b in Acetonitril rnit Tris(pbromphenyl)ammoniumylhexachloroantimonat 3 als Einelektronenoxidationsmittel umgesetzt"'l.Vollstandiger Umsatz konnte mit 200 Mol-Oh 3 erreicht werden, was auf eine formale 2e-Oxidation schliekn IaDt. In guten Ausbeuten werden bei kurzen Reaktionszeiten (ca. 20 s) die Benzo-furane4['3*'41gebildet(82%4a, 85% 4b). AuchTris(o-phenanthrolin)eisen(nr)-hexafluorophosphat 5, das als ,,Outer-K O H -CH,CN % eR / Mes Mes R ' hies R I 1 4 sphere"-O~idationsmittel~'~~ bekannt ist, ermoglicht die Synthese von 4 in guten Ausbeuten (91 YO 4a, 81 YO 4b).Nach Isolierung der Benzofurane 4 konnte durch cyclovoltammetrische Messungen gezeigt werden, daD die zweite Oxidationswelle bei der Enol-Oxidation (Abb. 1) von den an der Elektrode gebildeten Benzofuranen herruhrt Hiermit liegen genugend Indizien vor, um die Annahme von

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A Facile Synthesis of β‐Selenolactams

Ishihara

Yoshimi

Katō

1990

Angew. Chem. Int. Ed. Engl.

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The silaamidide anion of 2 reacts rapidly with HBr and tBuOH. Since silylamines are prone to cleavage by strong acids, Ph,PHBr was utilized as a gentle source of HBr.[@ It reacts with 2 in solution over several hours at room temperature, protonating one nitrogen atom and adding across the double bond of the silaamidine to afford 5. Chlorosilane 1 does not react under these conditions. Compound 2 reacts with tBuOH to yield 6. Addition of nBuLi to 2 followed by quenching with water gives 7, presumably by addition of nBuLi across an S i E N bond to form the dianion, which is then protonated. R = 2,4,6-tBu,C,H, Ph 2 Ph 3 L J 4in which the lithium cation is coordinated to two N atoms of silaamide and to one molecule of diethyl ether. Ether may be reversibly removed from 2 by heating at 160 " C for several hours under vacuum to give the ether-free silaamidide salt 3.Addition of [I 51crown-5 to a benzene solution of 2 yields the salt 4 in the form of large yellow benzene-containing crystals. The lithium cation is no longer coordinated to the two N atoms, and the crystals lose benzene on exposure to X-rays and become a powder that cannot be fully characterized. The silaamidide salts are thermally stable but decompose rapidly upon exposure to atmospheric moisture or oxygen. Angen. Chem. In(. Ed. Engl. 29 (1990) No. 5 Q VCH Verlagsgesellschaft mbH, 0-6940 Weinheim, 1990 0570-0833/90/0505-0531 8 02.50/0

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The Synthesis of the β‐Lactam Function

Cited by 9 publications

References 253 publications

Stereochemical Aspects of a Two-Step Staudinger Reaction − Asymmetric Synthesis of Chiral Azetidine-2-ones

Stereochemical Aspects of a Two-Step Staudinger Reaction − Asymmetric Synthesis of Chiral Azetidine-2-ones

Eine einfache Synthese von β‐Selenolactamen

A Facile Synthesis of β‐Selenolactams

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