Synthese und Reaktionen von Isothiocyanat‐substituierten Allenen und 1,3‐Butadienen

Banert, Klaus; Hückstädt, Holger; Vrobel, Kai

doi:10.1002/ange.19921040120

Cited by 23 publications

(1 citation statement)

References 11 publications

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“…Die Reaktionen von 10 zu 15 a oder 16 a ± d erfordern keine erhöhten Temperaturen und gelingen in Eintopfverfahren. Während die Produkte 12 a und 14 a der [3,3]-sigmatropen Umlagerungen als trennbare E/Z-Gemische entstehen, liefern die [2,3]-Isomerisierungen aus-schlieûlich die E-konfigurierten Diene 15 a, 16 a ± d und 18 a,c; die Sulfoxide 16 a ± d liegen wegen der Chiralitätszentren am Schwefel als like/unlike-Diastereomerengemische vor. [15] Bei der Thermolyse in Lösung findet keine nachträgliche Isomerisierung der Doppelbindung statt; so liefert die Umwandlung 13 ag 314 ag sowohl bei geringen Umsätzen als auch bei sehr langen Reaktionszeiten (ca.…”

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Synthese 1,2-difunktionalisierter 1,3-Butadiene durch Sequenzen sigmatroper Umlagerungen

1998

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Synthese 1,2-difunktionalisierter 1,3-Butadiene durch Sequenzen sigmatroper Umlagerungen

1998

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Synthesis of New Vinyl Thiocyanates by [3,3] Sigmatropic Rearrangement of Isothiocyanates

2001

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Keywords: Alkynes / Allenes / Dienes / Isothiocyanates / Rearrangements / ThiocyanatesPropargyl isothiocyanates 3 and buta-2,3-dienyl isothiocyanates 20 were prepared conventionally from amines and thiophosgene, or by a new, one-pot procedure using nucleophilic substitution to generate azides, which in turn served as the starting materials for a Staudinger reaction, followed by treatment of the resulting iminophosphoranes or iminophosphates with CS 2 . Equilibration, through a [3,3] sigmatropic rearrangement, of 3 and the allenyl thiocyanates 4 was established by flash vacuum pyrolysis or by thermolysis in solution. Even the reversible isomerization of the parent compounds 3f and 4f favors the allenyl thiocyanate. In the case of 20, an irreversible rearrangement reaction gave high yields of 2-thiocyanatobuta-1,3-dienes 21. A sequence of two [3,3] migration steps transformed 1,4-diisothiocyanatobut-2-ynes 3m and 3n into 2,3-dithiocyanatobuta-1,3-di-

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Regioselective Synthesis of Heterospirocyclic Isobenzofuranones and Medium-Sized Lactones by Multiple Anion Capture Reactions of 1,3-Dianions

2001

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The multicomponent reaction of 1,3-dianions with ketones and oxalic acid dichloride or diethylmalonic dichloride afforded six-to eight-membered lactones. Treatment of the dianion of 3-acetylindole with benzophenone and diethylmaDomino and multi-component reactions have found widespread applications in organic synthesis. [1] Multiple anion capture reactions involve attack of a carbanion on a relais species to form an intermediate which is subsequently reacted with an electrophile. Recent examples include the reaction of carbon nucleophiles with allenes and subsequent cyclization with acrylates, [2] and reactions involving isocyanates [3] or allenyl isothiocyanates as the relais species. [4] Multiple anion capture reactions involving nitriles as the relais species have been observed in the reaction of bislithiated 2,3-methylbutadiene with benzonitrile, [5] and in the 1,4-addition of nitriles to (butadiene)zirconocene. [6] In the course of our program [7] directed at the development of cyclization reactions of dianions [8] and dianion equivalents with dielectrophiles, we have recently studied nitriles as relais species in reactions of 1,3-dianions [9aϪ9c] and dilithiated allenes. [9d] We wish to report full details of our studies related to multiple anion capture reactions of 1,3-dianions with ketones and carboxylic acid dichlorides. [10] These reactions provide an efficient access to medium-sized lactones and novel heterospirocyclic isobenzofuranones. [11Ϫ13] Results and Discussion Synthesis of Lactones and Silyl EthersChlorosilanes were used in our first experiments aimed at demonstrating the concept of multiple anion capture reactions of dianions with ketone relais species. The dianion [14] of 1,1-diphenylacetone 1 was generated by treatment of 1 with potassium hydride and nBuLi. The dianion was condensed in situ with one equivalent of benzophenone 2a to give the dianionic intermediate A by regioselective attack of the terminal carbon atom of the dianion at the carbonyl group. Owing to steric and electronic reasons (delocaliz- [a] 1511 lonic dichloride resulted in the formation of a cyclic 1,3,5-triketooctene. The reaction of 1,3-dianions with ketones and phthalic dichloride resulted in the formation of heterospirocyclic isobenzofuranones rather than of medium-sized rings.ation of the negative charge through the phenyl rings), the carbon attached to the phenyl groups is less nucleophilic than the terminal carbon of the dianion. Subsequent addition of Me 3 SiCl gave the open-chain silyl ethers 3a and 3b in high yields (Scheme 1). Reaction of intermediate A with dichloro-diphenylsilane afforded the 1,3,2-dioxasilinane 3c in 76% yield. Scheme 1. Reaction of the dianion of 1,1-diphenylacetone with benzophenone and chlorosilanes Three-component cyclizations of dianions with ketones and dicarboxylic acid dichlorides were studied next. These reactions can, in principle, result in the formation of different regioisomeric cyclization products, as well as macrocyclic or polymeric products. In fact, we have found that...

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Synthese und Reaktionen von Isothiocyanat‐substituierten Allenen und 1,3‐Butadienen

Cited by 23 publications

References 11 publications

Synthese 1,2-difunktionalisierter 1,3-Butadiene durch Sequenzen sigmatroper Umlagerungen

Synthese 1,2-difunktionalisierter 1,3-Butadiene durch Sequenzen sigmatroper Umlagerungen

Synthesis of New Vinyl Thiocyanates by [3,3] Sigmatropic Rearrangement of Isothiocyanates

Regioselective Synthesis of Heterospirocyclic Isobenzofuranones and Medium-Sized Lactones by Multiple Anion Capture Reactions of 1,3-Dianions

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