Lichtinduzierte Reaktionen, XIV. Regeln zur Bestimmung von Spektren bei 2,4‐Cyclohexadien‐1‐onen

Quinkert, Gerhard; Dürner, Gerd; Kleiner, E. M.; Adam, Friedhelm; Haupt, Erhard T. K.; Leibfritz, Dieter

doi:10.1002/cber.19801130618

Cited by 22 publications

(8 citation statements)

References 44 publications

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“…Die UV/VIS-Absorptionsspektren von 2,4-Cyclohexadienonen (s. Fig. 3 ) zwischen 220 und 400 nm sind in [7c] [22] erortert worden. Besonders in unpolaren Solventien lassen sich die beiden typischen Absorptionsgebiete gut nebeneinander erkennen: die bei grosseren Wellenzahlen gelegene und durch hohere Intensitat ausgezeichnete n*, n-Absorption sowie die hierzu bathochrom verschobene, urn eine Zehnerpotenz weniger intensive und mit Schwingungsfeinstruktur ausgestattete n *, nAbsorption.…”

Section: 2)unclassified

“…Durch Vergleich der NMR-Spektren der Dienketene aus 6-Methyl-6-phenyl-2,4-cyclohexadien-l-on und 6,6-Dimethyl-2,4-cyclohexudien-l-on (s. [7d]: Abb. 24) erfuhr man, dass im ersteren Fall ein binarer Phototransient (Konfigurationsisomere in bezug auf die (C(S)=C (6) [22]: Abb. 1) topographisch weitgehend ubereinstimmen.…”

Section: 43)unclassified

“…1) topographisch weitgehend ubereinstimmen. Dafur spricht die Regelmassigkeit, mit der gewisse spektroskopische Eigenschaften (Lage der Maxima des n*, n-Absorptionsbereichs; chemische Verschiebung aller Ringkohlenstoffatome in den "C-Spektren) von Anzahl(0 bis 4) und Position (C(2) bis C(5)) weiterer CH,-Gruppen abhangen [22]. Die Konformeren der 2,4-Cyclohexadien-1-one haben ihre Ringzentren nichtplanar angeordnet.…”

Section: 43)unclassified

“…HPLC (Petrolether/Et20 10:0,5; 2 Silica-Kartuschen (Waters), 0,l l/min) und erneuter Kugelrohrdestillation: 644 mg (64 %) analysenreiner ( 3 Z.5 E)-6-Acetoxyheptu-3.5-diensuure- (47) Fig. 3; Herstellung s. [22] O( 1) (s. Fig. I ) bestimmt.…”

Section: A)unclassified

“…Eine Lsg. von 207 mg (0,99 mmol) rue-41 (Herstellung s. [22]: Abschnitt 5.9) und 3 ml (24,8 mmol) frisch destilliertem Cyclohexylamin in 120 ml H,O-freiem Et20 wurde unter Reaktionskontrolle durch DC (Cyclohexan/AcOEt 2:l) 40 min hestrahlt (s. E.rper. 1.1.1.1).…”

Section: Einstrahlen In Das Signal Von H-c(2) Zeigte Betrachtliche Wiunclassified

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Über Dienketene aus o‐Chinolacetaten

Quinkert

Kleiner

Freitag

et al. 1986

Helvetica Chimica Acta

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(RS)- 6-acetoxl.-5,.6-dimeth?.l-, (RS)-6-ucetoxy-2,4,6-1rimeth~.l-, 3,4,6-tet r m n i 4 i j~l -. and (RS)- 6-oci~tox~-2,3,4,5,6-pentumeth~l-2,4-c~clo/ie.~udii~n-I-oni~.~ serve as representative educts.Thcrc arc two separate main photochemical routes conveniently designated as l(n*, n) or '(n*, n ) tracks. The latter may also he attained by sensitization and leads to phenols. The former, by a-cleavage furnishes dien-ketens as indispensable phototransients. Photolysis of dien-ketens follows one or more of three reaction channels, each of which yields a particular type of photoproduct: heat-induced monocyclization affords 2,4-cyclohexadien-1-ones, heat-induced hicyclization stereoselectively furnishes bicyclo[3.1.0]hex-3-en-2-ones, and multi-step addition of protic nucleophiles stereosclcctively gives l,4-, I,6-and/or 1,2-adducts. By X-ray analysis or NOE studies, the structure of isolated photoproducts is establishcd. Conventional spectroscopy at low or flash spectroscopy at normal temperature yield information on the Cormation and decay of kinetically unstable intermediates. Photoproduct composition depends on the pattern o C substitution of the educts, o n thc solvents, and on the nucleophiles that might he present. Substituents primarily exert an influence upon the population of the various conformers of the dien-ketcn. Solvents affect the rate of the divers reaction paths competing for the phototransient. Nucleophiles play more than a trivial role when adducts are formed. With the detailed view of a dien-keten's role on hand, the photoproduct from a given o-quinol-acetate -or more general from a linear conjugatcd cyclohexadienone -is now predictable.

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Section: 2)unclassified

Section: 43)unclassified

Section: A)unclassified

Section: Einstrahlen In Das Signal Von H-c(2) Zeigte Betrachtliche Wiunclassified

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Über Dienketene aus o‐Chinolacetaten

Quinkert

Kleiner

Freitag

et al. 1986

Helvetica Chimica Acta

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Preparation of α,β‐Unsaturated Carbonyl Compounds and Nitriles by Selenoxide Elimination

Reich

Wollowitz²

1993

Organic Reactions

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Hydrogenation and dehydrogenation reactions play a key role in synthetic organic chemistry. The discoveries that selenium and sulfur substituents could be easily introduced α to a variety of acidifying functional groups, and that these derivatives could be smoothly converted to olefins by selenoxide or sulfoxide syn elimination under mild conditions greatly broadened the range of α,β‐unsaturated carbonyl compounds that could be prepared from their saturated analogs. This chapter covers the preparation from enols or enolates of α‐RSe substituted carbonyl compounds and nitriles and their conversion to olefins by thermolysis of the derived selenoxides. Other procedures for preparing these compounds are discussed in a limited way, and they are included in the tables, but the two‐step dehydrogenation is by far the most frequently used. The rapid acceptance of the selenoxide elimination as a synthetic procedure was the result of two factors: the ease with which many organoselenium compounds could be prepared using readily available, powerful electrophilic and nucleophilic selenium reagents, and the mild conditions (−50° to 40°) under which selenoxides fragment to olefins. Recognized selenoxide eliminations to form olefins were reported in 1967 and 1970, well after the related sulfoxide eliminations had been studied extensively. The application of the sulfoxide and selenoxide eliminations were reported almost simultaneously by several groups in 1973. These reactions have been the subject of several reviews. The principal procedures and reagents for the preparation of the requisite selenium compounds were also identified at that point. Preparations discussed in this chapter are Method A: Reaction of enolates, enols, enol ethers, and enamines with benzeneselenenyl chloride or bromide, or diphenyl diselenide. Method B: Reaction of enols with seleninylating agents [C 6 H 5 Se(O)Cl, (C 6 H 5 SeO) 2 O]. Method C: Nucleophilic substitution of α‐halo carbonyl compounds with metal selenolates. Method D: Alkylation of α‐phenylseleno carbonyl compounds and acylation of α‐lithio selenides or selenoxides.

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