Zur Erzeugung von Silaethenen des Typus R2Si=CH(SiR3 ) und R2Si=CH2 durch thermische Salzeliminierung sowie zur Kenntnis von R2Si=CH(SitBu3) (R = Me, tBu ) / On the Generation of Silaethenes of the Types R2Si=CH(SiR3) and R2Si=CH2 by Thermal Salt Elimination and on the Knowledge of R2Si=CH(SitBu3) (R = Me, tBu)

1996 ◽  
Vol 51 (12) ◽  
pp. 1744-1760 ◽  
Author(s):  
Nils Wiberg ◽  
Ch. M. M. Finger ◽  
T. Passler ◽  
S. Wagner ◽  
K. Polborn
Keyword(s):  
Diels Alder ◽  
X Ray ◽  
Reaction Intermediate

The generation of silaethenes Me2Si=CH(SiMe3) (1), Me2Si=CH(SitBu3) (2), tBuMeSi=CH(SitBu3) (3), and tBu2Si=CH2 (4) from metal organyls >SiX-CM< (X = Br, F; M = Na, Li) by elimination of MX is investigated. The metal organyls are prepared from >SiX-CBr< and RM (R = tBu3Si, nBu, Ph) by Br/M exchange (for preparation of >SiX-CBr< cf. Scheme 1). Only the sterically overcrowded silaethenes 2 and 3. generated from Me2SiF-CHNa(SitBu3) and tBuMeSiF-CHNa(SitBu3), have been identified by trapping with isobutene and dimethylbutadiene under formation of ene and Diels-Alder adducts. Analogous products are not found from Me2SiBr-CHNa(SiMe3) and tBu2-SiBr-CH2-Li. In the absence of trapping agents, compounds 1, 2, and 3 form cyclodimers. A reaction intermediate of the formation of 1 × 1 has been isolated and the structures of 2 × 2 and 3 × 3 have been solved by X-ray analysis. No dimer is observed for 4. In this case compounds are formed which may be interpreted as insertion products of 4 into the CLi bond of the precursor.

Structural Study of an Unusual Diels-Alder Adduct

1992 ◽  
Vol 45 (12) ◽  
pp. 2089 ◽  
Author(s):  
EL Ghisalberti ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Structural Study ◽  
Spectroscopic Studies ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Chemical Evidence ◽  
Alder Adduct

The structure of the compound obtained on heating the naturally occurring clerodane furanoditerpene (1) had been formulated as (2) on the basis of spectroscopic studies. A single-crystal X-ray diffraction study on the dihydro derivative of (2) has confirmed this and provides support for the stereochemistry previously assigned to (1) on the basis of chemical evidence.

scholarly journals Synthesis and Optoelectronic Properties of Iptycene–Naphthazarin Dyes

Synlett ◽  
2018 ◽  
Vol 30 (01) ◽  
pp. 54-58 ◽  
Author(s):  
Timothy Swager ◽  
Cagatay Dengiz ◽  
You-Chi Wu
Keyword(s):  
Single Crystal ◽  
Electronic Properties ◽  
Diels Alder ◽  
Optoelectronic Properties ◽  
Synthesis And Characterization ◽  
Nmr Analysis ◽  
X Ray ◽  
Vis Spectroscopy

We report the synthesis and characterization of iptycene–naphthazarin dyes by using a sequential Diels–Alder approach. The tautomerization of naphthazarin was used as the key step in the synthesis, with structures confirmed by single-crystal X-ray and NMR analysis. The systematic trends in electronic properties were investigated by UV/Vis spectroscopy. BF2 complexes of the dyes were prepared by reaction with BF3·OEt2 in CH2Cl2.

New, Homochiral Synthons Obtained through Simple Manipulations of Enzymatically Derived 3-Halo-cis-1,2-dihydrocatechols

2015 ◽  
Vol 68 (10) ◽  
pp. 1467 ◽  
Author(s):  
Lorenzo V. White ◽  
Ping Lan ◽  
Brett D. Schwartz ◽  
Anthony C. Willis ◽  
Martin G. Banwell
Keyword(s):  
Single Crystal ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
X Ray

The bromoepoxide 5a, which is obtained from the homochiral and enzymatically derived cis-1,2-dihydrocatechol 1a, is readily and efficiently transformed into either isomer 8a or the corresponding methoxymethyl-ether 2a. Though both of these products can be fully characterized, they are somewhat unstable, with the former being converted into the crystalline enone 3a on standing and the latter readily participating in a Diels–Alder cycloaddition reaction with the potent dienophile N-phenyl-1,2,4-triazoline-3,5-dione to give adduct 7a. The single-crystal X-ray structures of compounds 3a and 7a are reported. Using the related chemistry the chloro-analogue, 3b, of enone 3a can be obtained.

Laboratory Stopped-Flow XAFS Apparatus. Structure Determination of the Short-Lived Peroxochromium Intermediate Formed during Reduction Process of Chromate(VI) Ion by Hydrogen Peroxide

1997 ◽  
Vol 52 (6) ◽  
pp. 711-718 ◽  
Author(s):  
Y. Inada ◽  
S. Funahashi
Keyword(s):  
Hydrogen Peroxide ◽  
Fine Structure ◽  
Water Molecule ◽  
Reduction Process ◽  
Stopped Flow ◽  
Structure Parameters ◽  
X Ray ◽  
Reaction Intermediate ◽  
X Ray Absorption

In order to determine the structure parameters of the reaction intermediate formed during the reduction process of chromate(VI) ion by hydrogen peroxide, a laboratory stopped-flow X-ray absorption fine structure (XAFS ) apparatus, which was constructed by a rotating anode X-ray generator, an energy scanning spectrometer, a stopped-flow assembly, and X-ray detectors, was newly developed. Using the apparatus, the Cr K -edge XAFS spectrum of the reaction intermediate was measured. One oxo group, two peroxo groups, and one water molecule are coordinated to the Cr(VI) center in the intermediate, CrO(O2)2(H2O ) , with Cr - O bond lengths of 157, 168, and 193 pm, respectively. The geometry around the Cr(VI) center is probably 6-coordinate pentagonal pyramidal.

Synthesis and x-ray structure of a Diels-Alder adduct of fullerene C60

1993 ◽  
Vol 115 (1) ◽  
pp. 344-345 ◽  
Author(s):  
Yves Rubin ◽  
Saeed Khan ◽  
Daron I. Freedberg ◽  
Chahan Yeretzian
Keyword(s):  
Diels Alder ◽  
Fullerene C60 ◽  
X Ray ◽  
Alder Adduct

Ultrafast X-Ray Solution Scattering Reveals an Unknown Reaction Intermediate in the Photolysis of [Ru3 (CO)12 ]

2008 ◽  
Vol 120 (30) ◽  
pp. 5632-5635 ◽  
Author(s):  
Qingyu Kong ◽  
Jae Hyuk Lee ◽  
Anton Plech ◽  
Michael Wulff ◽  
Hyotcherl Ihee ◽  
...  
Keyword(s):  
X Ray ◽  
Reaction Intermediate

Einfache Synthese von 2,2-Diethoxy-2,5-dihydrofuranen, 2(5 H)Furanonen und 2-Ethoxy-furanen.Kristall-und Molekülstruktur eines Barrelenon Diels-Aider Produktes [1] / Convenient Synthesis of 2,2-Diethoxy-2,5-dihydrofurans, 2(5 H)Furanones and 2-Ethoxyfurans.Crystal and Molecular Structure of a Barrelenone Diels-Alder Product [1]

1994 ◽  
Vol 49 (3) ◽  
pp. 389-406 ◽  
Author(s):  
Rolf W. Saalfrank ◽  
Wieland Hafner ◽  
Joachim Markmann ◽  
Andreas Welch ◽  
Karl Peters ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Maleic Anhydride ◽  
Structure Analysis ◽  
Diels Alder ◽  
Dimethyl Acetylenedicarboxylate ◽  
Reaction Conditions ◽  
X Ray ◽  
Convenient Synthesis

AbstractReaction of 1,2-hydroxyketones 5 with (2,2-diethoxyvinylidene)triphenylphosphorane (2) or (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborates 6 yields the 2,2-diethoxy- 2.5-dihydrofurans 9. Depending on the reaction conditions used, the orthoesters 9 can be hydrolized to give 2(5 H)furanones 10 and 2-ethoxyfurans 11, respectively. 4,5-Dimethyl- 5.6-dihydro-2-pyranone (20) and 8-methoxycoumarin (23) are prepared, starting from (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborate (6 a) and 1-hydroxy-2-methyl- 3-butanone (16) or 2-hydroxy-3-methoxy-benzaldehyde (21). The 2-ethoxyfuranes 11 readily undergo Diels-Alder reactions with 2-chloracrylonitrile (24), maleic anhydride (26), N-phenyl-1,2,4-triazoline-3,5-dione (28) and dimethyl acetylenedicarboxylate (30) to give the corresponding Diels-Alder products 25, 27, 29 and 31, respectively. Contrary to 2-ethoxyfuran 11b , 11a reacts with two equivalents of acetylene 30, to yield barrelenone 34. The structure of 34 unequivocally is established by X-ray structure analysis.

A general intramolecular Diels–Alder approach to tricyclic sesquiterpenes: stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene

1987 ◽  
Vol 65 (1) ◽  
pp. 114-123 ◽  
Author(s):  
Kazimierz Antczak ◽  
John F. Kingston ◽  
Alex G. Fallis ◽  
Alfred W. Hanson
Keyword(s):  
Double Bond ◽  
Methyl Ester ◽  
Ring System ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Total Syntheses ◽  
Methyl Group ◽  
X Ray ◽  
12 Steps ◽  
Selective Hydrogenolysis

Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl-2-pentenoate 13c affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (14c), which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function by elimination and hydrogenation (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 12 steps from aldehyde 7. A parallel series of reactions employing the isopropyl triene epimer 13a affords (±)-5-epi-sinularene. X-ray analyses of the triene 13a and the adduct 14a are also reported.

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