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61.
62.
A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-ones The reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50–80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded. 相似文献
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The influence of surface structure of technical materials on results and statements of surface analytical methods has been investigated. Especially surface roughness as a typical property of rolled products has been observed. For this purpose samples of steel (technical surface, roughness up to 5 m) and silicon wafers (polished surface) have been analyzed by SNMS and GDOS in order to get information about changes of the surface roughness as function of the sputtering time and their influence on the statements about the depth profiles obtained. 相似文献
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Dipolar 1:1 Adducts from the Reaction of 3-Amino-2H-azirines with 1,3,4-Oxadiazol- and 1,3,4-Thiadiazol-2(3H)-ones 3-Amino-2H-azirines 1 react with 5-(trifluoromethyl)-1,3,4-oxadiazol-2(3H)-one ( 2 ) as well as with different 5-substituted 1,3,4-thiadiazol-2(3H)-ones ( 5a–e ) in 2-propanol at room temperature to give dipolar 1:1 adducts of type 3 and 6 , respectively, in reasonable-to-good yields (Schemes 3 and 6, Tab. 1 and 2). The structure of two of these dipolar adducts, 6a and 6e , which are formally donor-acceptor-stabilized azomethin imines, have been elucidated by X-ray crystallography (Figs. 1-4). In the reaction of 2 and sterically crowded 3-amino-2H-azirines 1c–e with a 2-propyl and 2-propenyl substituent, respectively, at C(2), a 4,5-dihydro-1,2,4-triazin-3(2H)-one of type 4 is formed as minor product (Scheme 3 and Table 1). Independent syntheses of these products proved the structure of 4 . Several reaction mechanisms for the formation of compounds 3 and 4 are discussed, the most likely ones are described in Scheme 4: reaction of 2 as an NH-acidic compound leads, via a bicyclic zwitterion of type A , to 3 as well as to 4 . In the latter reaction, a ring-expanded intermediate B is most probable. 相似文献
69.
The chemistry of [Re(CO)(NO)L2] fragments (L ? phosphorus donor) was explored. Starting from [Re(CO)5Cl] the synthesis of [Re2Cl2(μ-Cl)2(CO)4(NO)2] ( 1 ) was accomplished via the preparation of [Et4N]2[Re2Cl2(μ-Cl)2(CO)6] and nitrosylation of this compound with [NO][BF4]. Complex 1 was converted to [RecL2(CO)(NO)L2] complexes 2 ( a L = (MeO)3P; b L = (EtO)3P; c L = (i-PrO)3P; d L ? Me3P; e L ? Et3P; f L ? Cy3P) by heating with L in MeCN. In the case of the reaction of L = (MeO)3P, a trisubstitued compound mer-{ReCl2(NO)[P(OMe)3]3} 3 was also obtained. Replacement of the Cl ligands in 2a–e with Me groups was achieved by reacting them with MeLi in Et2O yielding cis, trans-[Re(CO)(NO)Me2L2]complexes 4a–e . Reaction of 2a–e with Li[BHEt3] led to substitution of one Cl by an H ligand with formation of [ReCl(CO)H(NO)L2] compounds 5a–;e , displaying trans-H,NO geometries. The hydride-transfer agent Na[AlH2(OCH2CH2OCH3)2] transformed 2 into the cis-dihydride systems [Re(CO)H2(NO)L2] 6a–f . Reductive carbonylation of 2a–d in the presence of Na/Hg and CO gave pentacoordinate [Re(CO)2(NO)L2] complexes 7b–d , and under comparable conditions the Cl substituents of 2b–f were replaced by tolane using Mg or t-BuLi giving trigonal bipyramidal [Re(CO)(NO)L2(PhC?CPh)] compounds 8b–f . Complexes 5c , 6a , and 8d were characterized by X-ray crystal-structure analysis. 相似文献
70.
Heinz Berner Gerhard Schulz Gernot Fischer Hellmuth Reinshagen 《Monatshefte für Chemie / Chemical Monthly》1978,109(3):557-566
In order to obtain a better partition of a prodigiosin derivative in biological media, two hydroxy groups were introduced into theansa-part of the molecule. The synthesis of the title compound is described in detail. 相似文献