Photolysis of 7,8-digermabicyclo[2.2.2]octadiene. The investigation of the elementary stages by means of 1H CIDNP and laser pulse photolysis (original) (raw)
Photochemistry of 1-(2,6-dichlorobenzyl)-1,4-dihydronicotinamide
Tetrahedron Letters, 1985
1,4,5,6-tetrahydropyridines Via and VIb were obtained. The investigation on the photochemistry of NADH and model compounds is centered around the electron-transfer processes and the reducing properties of these substances.' Few works are devoted to the photocycloadditions of 1,4-dihydropyridines which take place in nonoxidizing conditions, with high regio-and stereo-specificity: 1,4-dihydropyridine-3,5-dicarboxylate dimerizes giving head-to-tail-= and head-to-tail-anti dimers,2 1-benzyl-1,4-dihydronicotinamide (BNAH) give head-to-tail--dimer 3 or, in the presence of acrylonitrile, photoadducts across the 2-3 double bond. 4
2014
The synthesis of the first member of a new class of Dewar benzenes has been achieved. The synthesis of 2,3- dimethylbicyclo[2.2.0]hexa-2,5-diene-1, 4-dicarboxylic acid and its anhydride are described. Dibromomaleic anhydride and dichloroethylene were found to add efficiently in a photochemical [2+2] cycloaddition to produce 1,2-dibromo- 3,4-dichlorocyclobutane-1,2-dicarboxylic acid. Removal of the bromines with tin/copper couple yielded dichloro- cyclobutenes which added to 2-butyne under photochemical conditions to yield 5,6-dichloro-2,3-dimethylbicyclo [2.2.0] hex-2-ene dicarboxylic acids. One of the three possible isomers yielded a stable anhydride which could be dechlorinated using triphenyltin radicals generated by the photolysis of hexaphenylditin. Photolysis of argon matrix isolated 2,3-dimethylbicyclo [2.2.0]hexa-2, 5-diene-1,4-dicarboxylic acid anhydride produced traces whose strongest bands in the infrared were at 3350 and 600 cm^(-1). This suggested the formation of termi...
The photolysis of 2,4,5,6-tetrachloro-1,3,-dicyanobenzene
Journal of Photochemistry and Photobiology A: Chemistry, 1989
undergoes extensive transformation to many photoproducts of single and sequential excitation on UV irradiation in ethanol. Cl *H and CN + H exchange take place with the solvent, and solvent incorporation occurs followed by cyclization on the cyano group(s) and/or further side-chain deoxygenation. Cl + Et exchange is also observed. The photoproducts were identified by gas chromatographymass spectrometry (GC-MS). Some were isolated and analysed by IR and nuclear magnetic resonance (NMR) spectroscopy, which provided evidence for their structural identification. o-Chlorobenzonitrile was found to yield only the product of photoreduction of the C-Cl bond.
Photochemistry of bridged cycloheptadienones
Tetrahedron, 1974
A series of 6,7-Benzobicyclol3.2.l]octadienes (10-13) have been prepared. Direct and sensitized irradiation of the dienes gave di-m-methane rearrangement products (M-17). Quantum yields for the direct and sensitized rearrangements were recorded and compared. Substituent effect and structure-multiplicity relationships are discussed.
Journal of Photochemistry and Photobiology A: Chemistry, 2009
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Journal of Organic Chemistry, 1985
The thermolysis and 350-nm and 185-nm photolyses of the azoalkanes 2,3-diazabicyclo[2.2.l]hept-2-ene (la) and spiro[cyclopropane-1,7'-[2,3]diazabicyclo[2.2.l]hept-2-ene] (lb) have been investigated. The exo/endo stereochemistry in the bicyclo[2.l.Q]pentanes 2a,b and in the rearranged olefin 3b w a~ determined by deuteration experiments using 5,6-exo-dideuterioazoalkanes la,b-d2. Whereas thermal and direct photochemical (350 nm; n, T * ) denitrogenation of azoalkane la-d2 led exclusively (>99%) to bicyclo[2.1.0]pentane 2a-dz with preferential (1.54, 2.94) double inversion, the triplet-sensitized photolysis afforded nearly complete stereoequilibration. In 185-nm denitrogenation an unexpectedly high exo/endo ratio (3.1) for bicyclo[2.1.O]pentane 2a-d, was found, besides isomerization to cyclopentene 2a-dz. Similar results were obtained in the denitrogenation of spiroazoalkane lb-d2, which exhibited exo stereochemical preferences in both photoproducts spiro[bicyclo[2.1.0]pentane-5,1'cyclopropane] 2b-d2 and bicyclo[3.2.0]hept-l-ene 3b-d2. The 350-nm photolysis of azoalkane lb-d, gave preferential formation of ezo-spirobicyclo[2.1.O]pentane 2b-d2 and exo-olefin 3b-d2, whereas triplet-sensitized decomposition yielded almost complete loss of stereochemical preference in the olefin 3b-dz. The 185-nm photolysis of azoalkane lb-d2 showed similar behavior compared with the azoalkane la, e.g., a t high exo/endo ratio in spirobicyclo-[Z.l.O]pentane 2b-d2. Also olefin 3b was formed with complete stereoequilibration. These diverse experimental results are discussed in terms of one-bond vs. two-bond cleavage processes leading to the diazenyl diradicals D'n,,,
The Photolysis of 7-Ketonorbornene 1
The Journal of Organic Chemistry, 1965
The ultraviolet photolysis of 7-ketonorbornene has been studied in ethyl ether solution. With a Pyrex filter, the photodecomposition is very slow, giving carbon monoxide and 1,3-cyclohexadiene. With Corex or Vycor filters or in the absence of filters, 7-ketonorbornene efficiently gives carbon monoxide, 1,3-cyclohexadiene, and 1,3,5-hexatriene.
Photochemical Reactions of 1,3,3-Trimethylbicyclo[2.2.2]octa-5,7-dien-2-ones
European Journal of Organic Chemistry, 2006
The photochemistry of 1,3,3-trimethylbicyclo[2.2.2]octa-5,7-dien-2-ones 1a–f containing multiple chromophoric moieties under various conditions is described. Upon direct irradiation, dienones 1a–f in benzene, acetonitrile, and methanol were found to aromatize through photoelimination of dimethylketene, which was trapped with 3-phenylprop-2-en-1-ol (12). Triplet sensitization of dienone 1a in acetone and in acetone/acetophenone mixed solvents afforded aromatic compound 2a, whilst bicyclic systems 1b–c were found to be unreactive on sensitization. In the cases of dienones 1d–f in acetone, aromatic compounds 2d–f and di-π-methane (DPM) photoproducts 3d–f and 4f were observed, but in the acetone/acetophenone mixed solvent system only DPM photoproducts were detected. Plausible mechanisms for these photochemical reactions are described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)