| | 1 | Author
| Claudia Bäk, Klaus Praefcke | Requires cookie* | | | Title
| Photoreaktionen 2.2'-dihalogensubstituierter Benzoinether und Benzildimethylmonoketale in Lösung 1 Photoreactions of 2,2'-Dihalogen Substituted Benzoin Ether and Benzildimethylmonoketals in Solution  | | | | Abstract
| The synthesis of a,a'-dihalogenated benzoin ether 6 and benzildimethylmonoketals 7 are discribed. Their reaction behavior under UV irradiation and electron impact conditions are discussed in comparison with those of arylesters 1 of seleno and thiobenzoic acid. The photoproducts of 6 and 7 are separated and identified with help of column or vaporphase chromatography. Photoinduced a-cleavages of 6 and 7 produce 2-halogenbenzoyl radicals 9 and a-monomethoxybenzyl radicals 10 or a,a-dimethoxybenzyl radicals 15 resp., which undergo four different stabilization reactions under formation of 1) 2-halogenbenzaldehydes 12 from 9 by hydrogenabstraction, 2) 2,2'-dihalogenbenzils 11 and l,2-di(2-chlorophenyl)-1,2-dimethoxyethan (13) via dimerization of 9 or 10 resp., 3) methylesters 16 of 2-halogen-benzoic acids by /^-elimination of methylradicals from 15, and 4) 2-halogenacetophenones 17 via combination of 9 with methylradicals from 15. In addition to these photoproducts 2-phenylbenzoic acidester 18, benzaldehyde (19), and acetophenone (20) are formed by photosubstitution of halogens in benzaldehydes 12 as well as in acetophenones 17 against hydrogen and in benzoic acid-esters 16 against phenyl resp. Independent photoexperi-ments prove 1) the formation of 2-phenylbenzoic acidester 18 by halogen-phenylreplace-ment in 16 and 2) that chlorine is easier than bromine, both in orZ/io-position to a carboxyl function, substituted by phenyl. No photoproducts {e.g. 8 or 14) are formed by substitution of halogen in the 2-halogenbenzoyl part of a-cleavage against neither a-monomethoxybenzyl nor a,a-dimethoxybenzylradicals resp. as expected like the photoinduced formation of selenoxanthones or thioxanthones 2 from selenol-or thiolesters 1. | | | |
Reference
| (Z. Naturforsch. 33b, 106—112 [1978]; eingegangen am 5. Oktober 1977) | | | |
Published
| 1978 | | | |
Keywords
| Carbonyl Compounds, a-Cleavages, Free Radicals, Aromatic Photosubstitutions | | | |
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| | | | | TEI-XML for
| default:Reihe_B/33/ZNB-1978-33b-0106.pdf | | | | Identifier
| ZNB-1978-33b-0106 | | | | Volume
| 33 | |
| 2 | Author
| Martin Mittelbach, Hans Junek | Requires cookie* | | | Title
| Synthesen mit Nitrilen, LVII [1] Zur Reaktivität von Aminomethylen-malonsäuredinitrilen gegenüber Aldehyden und Orthoestern Syntheses with Nitriles, LVII [1] The Reactivity of Aminomethylene-malononitriles with Aldehydes and Orthoesters | | | | Abstract
| Condensation of aminomethy lene-malononitrile (la) with aromatic aldehydes and dimethylformamide-dimethylacetal, resp., leads to benzylidene-malononitriles (2 a, b) and to dimethylaminomethylene-malononitrile (2e), resp. A mechanism of this cleavage of a C = C double bond is discussed. Several substituted enaminonitriles (le-i) are prepared and the reactivity against aldehydes is studied. Thus, condensation of 3-Amino-2-cyano-crotononitrile (le) with aldehydes leads to 2-amino-4-phenyl-l,3-butadiene-l,l-dicarbo-nitriles (3). 4-Oxo-2-phenyl-l,2,3,4-tetrahydro-5-pyrimidine-carbonitriles (4) are yielded by the reaction of 3-amino-2-cyano-crotonic-carboxamide (lh) and 3-amino-2-cyano-cinnamamide (li), resp., with aldehydes. Condensation of lh and li with ethyl ortho-formate leads to 3,4-dihydro-4-oxo-pyrimidine-carbonitriles (6). | | | |
Reference
| Z. Naturforsch. 34b, 1580—1586 (1979); eingegangen am 13. Juli 1979 | | | |
Published
| 1979 | | | |
Keywords
| Aminomethylene-malononitrile, Aminomethylene-cyanoacetamide, Carbonyl Compounds, Orthoesters, Condensation | | | |
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| default:Reihe_B/34/ZNB-1979-34b-1580.pdf | | | | Identifier
| ZNB-1979-34b-1580 | | | | Volume
| 34 | |
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