Über Dihydrophenazonyl‐Radikale

Wittig, Georg; Schuhmacher, Alfred

doi:10.1002/cber.19550880213

Cited by 9 publications

(1 citation statement)

References 10 publications

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“…The equivalent hexadeuteriated alcohol [(CD,),C(OH)R] was prepared in an identical manner using CD3Li (from CDJ and lithium wire) 89%, m.p. (22), 81 (22), and 43 (100).…”

Section: -( 2-hydroxy-24-dimethyipent-3-ylidene)-2233-tetramethylcycl...mentioning

confidence: 99%

Use of the diazoalkane–thione reaction in the synthesis of a vinyltrimethylenemethane precursor

Bushby¹,

Mann²

1987

J. Chem. Soc., Perkin Trans. 1

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Previous studies have shown that the reaction of diazoalkanes with 3,5-dihydro-3,3,5,5-tetramethylpyrazole-4-thione ( 6 ) provide a flexible route for the synthesis of precursors to trimethylenemethane (TM M) (1 ) and tetramethylene-ethane (TM E) (2) biradicals. We now show that this route can be adapted for the synthesis of a precursor to another type of non-Kekul6 polyene, a vinyl-TMM biradical (3). The thermal isomerisation of 1 -(2,4-dimethylpent-l -en-3-ylidene) -2,2,3,3-tetramethylcyclopropane ( 2 7 ) to 4-isopropyl-3-isopropylidene-2,5-dimethylhexa-1,4-diene (I 1) which involves a vinyl-TMM intermediate (3-isopropyl-4-isopropylidene-2,5-dimethylhex-2-ene-I ,5-diyl) was shown by deuterium labelling to involve a 1,6-hydrogen shift. It is suggested that such sigmatropic rearrangements of non-Kekule polyenes may involve orbital symmetry control. Related examples are discussed. Two reactions discovered incidentally in the course of this work are of some interest, one involving the synthesis of an allylic amine through the thermal rearrangement of an aziridine (2-isopropyl-3,3-aziridine) (1 6) and the other the formation of an oxathiole ( 2 0 ) through the reaction of a thione ( 6 ) and an x-diazo ketone (3-diazo-4-methylpentan-2-one) (1 8 ) .Trimethqlenemethane (TMM) (1) '.' has 4 n electrons and is isomeric with butadiene. Since it is not possible to write a structure for T M M in which all 4 n electrons are paired, it is knobcn as a non-Kekule polyene' and as no 'closed shell' structure can be written. it seems reasonable to suppose that TMM will behave as a biradical. This simple expectation is confirmed both by experiment '.' and by molecular orbital calculations.3 TMM is in f x t the simplest member of a whole famil! of non-Kekule polyenes. There are two non-Kekule polyenes which have 6 n electrons and which are isomeric with hexatriene [tetramethylene-ethane T M E (2), and vinyl-TMM (311 and seven non-Kekule polyenes which have 8 n electrons .x.which are isomeric with octatetraene. In previous papers in this series we have shown that precursors to TMM 4.s and TME biradicals [for example compound (9)] could be elaborated from the thione (6). In the present paper we show that this same thione can be used to make a precursor to the less well knoivn type of 6 n electron non-Kekule polyene. a ~. i n~. l -TMM.7 The particular vinyl-TMM biradical which we wanted to study was 3-isopropyl-4-isopropylidene-2.5-dimethylhex-2-ene-1 S-diyl (4). Our interest in this particular biradical arose since it may well be an intermediate in the thermal isomerisation of the spiropentane (10) to the triene ( l l ) . 6Retrosynthetic analysis (Scheme 1 ) suggests that the vinyl-TMM (4) could be derived from the dihydropyrazole (5), which it should be possible to obtain from the addition reaction between the thione ( 6 ) and the diazoalkane (7).4-6 The initial objective was therefore the preparation of a precursor to the diazoalkane. the allylic amine (8). There are not many general routes to allylic amities but the synthesis of com...

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“…The equivalent hexadeuteriated alcohol [(CD,),C(OH)R] was prepared in an identical manner using CD3Li (from CDJ and lithium wire) 89%, m.p. (22), 81 (22), and 43 (100).…”

Section: -( 2-hydroxy-24-dimethyipent-3-ylidene)-2233-tetramethylcycl...mentioning

confidence: 99%

Use of the diazoalkane–thione reaction in the synthesis of a vinyltrimethylenemethane precursor

Bushby¹,

Mann²

1987

J. Chem. Soc., Perkin Trans. 1

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Electrophilic Amination of Carbanions, Enolates, and Their Surrogates

Ciganek

2009

Organic Reactions

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This chapter deals with the formation of carbon‐nitrogen bonds by reaction of carbon nucleophiles with electrophilic aminating reagents. The former encompass aliphatic and aromatic carbanions, enolates and their surrogates such as enamines, enol esters, and enol ethers, as well as carbanions stabilized by cyano or sulfone groups or by phosphorus. A section entitled Reagents and Mechanisms lists the many aminating reagents available and discusses the mechanisms by which the more important ones react. Among the electrophiles discussed are halo amines, various hydroxylamine derivatives, oxaziridines, imines, oximes, diazonium salts, diazo compounds, azo compounds, and azides. The section on Scope and Limitations is organized by carbon nucleophiles and attempts to suggest the best reagents for each class. A number of electrophilic aminating reagents that have been omitted from the scope of this chapter are briefly discussed, with references to reviews, in the section on Comparison with Other Methods. Tables listing references to the preparation of the various aminating reagents are found in the section on Experimental Conditions. References to the conversion of non‐amine products into amines are also provided there. The literature is covered to the middle of 2007.

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Organoalkali Chemistry

Schlosser

2013

Organometallics in Synthesis

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Über Dihydrophenazonyl‐Radikale

Cited by 9 publications

References 10 publications

Use of the diazoalkane–thione reaction in the synthesis of a vinyltrimethylenemethane precursor

Use of the diazoalkane–thione reaction in the synthesis of a vinyltrimethylenemethane precursor

Electrophilic Amination of Carbanions, Enolates, and Their Surrogates

Organoalkali Chemistry

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