Design and Synthesis of<i>α</i>‐Diketones. The Cyclobutane‐1,2‐dione Chromophore: Synthesis, Dienophilic Reactivity and Electronic Properties of Cyclobutenedione and Polycyclic Cyclobutanediones [1]

The energies of vertical electron attachment to cyclobutanone, its 2-and 3-oxa derivatives, 1,2-cyclobutanedione, and 2,2′,4,4′-tetramethyl-1,3-cyclobutanedione have been measured in the 0-6 eV energy range by means of electron transmission spectroscopy. The energies of temporary anion formation are nicely reproduced by shifting and scaling the virtual π* orbital energies calculated for the MP2/6-31G*-optimized geometries of the neutral molecules. The linear correlation between experimental and calculated energy values reported in the literature for the empty π* CC orbitals fits the present data on the π* CO orbitals with the same accuracy. The two π* anion states observed in the ET spectrum of the 1,3-dione (split by 1.25 eV) are assigned to the in-phase and out-of-phase combinations in order of increasing energy, i.e., the sequence dictated by throughspace interaction. The calculations indicate a large through-space splitting (>2 eV) of the empty carbonyl π* orbitals, reduced by through-bond destabilization of the in-phase combination.

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“…Synthesis. 2,2‘,4,4‘-Tetramethyl-1,3-cyclobutanedione ( 4 ) and 1,2-cyclobutanedione ( 5 ) were prepared following literature procedures. , …”

Section: Methodsmentioning

confidence: 99%

Temporary Anions and Empty Level Structure in Cyclobutanediones: Through-Space and Through-Bond Interactions

Modelli

Martin

2002

J. Phys. Chem. A

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“…The required α-dione 4 is a known compound and was prepared following the method reported by Martin et al [ 11 ] ( Scheme 2 a). Condensation of 4 with the Crossley diamine 5 [ 8 ] produced the porphyrin block 8 ( Scheme 2 b) that was characterised by spectroscopy and high resolution electrospray mass spectrometry (HR-ESMS) (found m / z 1307.8294).…”

Section: Resultsmentioning

confidence: 99%

Bis-Porphyrin Racks with Space-Separated Co-Planar Porphyrin Rings

Johnston

2001

Molecules

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“…Surprisingly, compound (1) proved to be unreactive in Diels-Alder cycloaddition, also with very reactive dienes such as cyclopentadiene or butadiene (generated in situ from 3-sulfolene), and even in the presence of Lewis acids (A1Cla), in contrast to the corresponding electron-deficient olefin, i.e. cyclobutene-l,2-dione [(2), R = H], which is a very reactive dienophile, because of both inductive and mesomeric effects and ring strain (Albert, Heller, Iden, Martin, Martin, Mayer & Oftring, 1985).…”

mentioning

confidence: 99%