Thermolysis of 3‐phenyl‐5‐arylamino‐1,2,4‐oxadiazole and thiadiazole derivativesGaber, Abd El‐Aal M.; El‐Emary, Talaat I.; Atalla, Ahmed A.
doi: 10.1002/(SICI)1098-1071(1997)8:4<287::AID-HC1>3.0.CO;2-8pmid: N/A
Thermal reactions of 3‐phenyl‐5‐arylamino‐1,2,4‐oxadiazoles I and II were investigated. Neat heating at ca. 250°C for 6 hours afforded H2O, benzonitrile, arylcyanamides, arylamines, azobenzene, benzimidazole derivatives, and 3,3′‐diphenyl‐5,5′‐bis[1,2,4‐oxadiazolyl]. Analogous results were obtained by the thermolysis of 3‐phenyl‐5‐anilino‐1,2,4‐thiadiazole III at ca. 200°C for 2 hours. In addition to H2S, NH3, and HNCS, phenyl isothiocyanate and thiocarbanilide were obtained. Thermolysis of III in quinoline as a radical trap gave analogous resuLts but also 2‐anilinoquinoline. A free‐radical mechanism has been suggested to account for the identified products. © 1997 John Wiley & Sons, Inc.
AM1 calculations of parts of the enthalpy surfaces for additions of active methylene nitriles to α β‐unsaturated nitrilesEl‐Taher, S.; Elnagdi, M. H.
doi: 10.1002/(SICI)1098-1071(1997)8:4<299::AID-HC3>3.0.CO;2-6pmid: N/A
The nucleophilic additions of active methylene nitriles (MNs), R1R2CH−, where R1=CN and R2=CN, and CSNH2, to acetaldehyde and to the resultant α, β‐unsaturated nitriles have been studied theoretically by the AM1 semiempirical MO method. The additions of MNs anions to acetaldehyde are found to be endothermic with late productlike transition states (TSs) on the reaction coordinate. Their additions to α,β‐unsaturated nitriles may conceivably proceed via two pathways: addition to the C=C double bond and addition to the C≡N triple bond. It has been found that the nucleophilic attack at the &alpha,β‐unsaturated linkage is exothermic, while that at the nitrile group is endothermic and has a relatively high enthalpy barrier. Both additions have late productlike transition states. The reactivity of the nucleophilic attack has been discussed in the light of the frontier molecular orbital theory and in terms of the HOMO–LUMO two‐electron interaction. The calculations have been compared with experimental results. © 1997 John Wiley & Sons, Inc.
Reactions of dithioxo‐1,3,2λ5,4λ5‐dithiadiphosphetanes with triorganolead derivativesNizamov, Il'yas S.; Kuznetzov, Vladislav A.; Batyeva, Elvira S.
doi: 10.1002/(SICI)1098-1071(1997)8:4<323::AID-HC6>3.0.CO;2-Bpmid: N/A
The reactions of Lawesson's reagent 1a and its 4‐ethoxy homologue 1b with triethyl‐ and triphenyl(alkoxy)plumbanes 2a,b and ‐(alkylthio)plumbanes 4a,b were studied. On the basis of these reactions, novel, advantageous methods of synthesizing S‐triethyl and triphenylplumbyl derivatives of aryldithio‐ and trithiophosphonic acids 3a–d and 5a,b were developed. © 1997 John Wiley & Sons, Inc.
Convenient methods for the synthesis of S‐organothioarsenic(III) derivatives of tetrathiophosphoric and trithiophosphonic acidsNizamov, Il'yas S.; Matseevskii, Alexey V.; Batyeva, Elvira S.; Abalonin, Boris E.; Vandyukova, Irina I.; Shagidullin, Roal'd R.
doi: 10.1002/(SICI)1098-1071(1997)8:4<329::AID-HC7>3.0.CO;2-5pmid: N/A
S‐Organoarsenic(III) derivatives of tetrathiophosphoric and trithiophosphonic acids 3a,b and 7 were easily obtained by the reactions of tetraphosphorus decasulfide 1, the ethyl homologue of Davy's reagent 5, and Lawesson's reagent 6 with S‐isobutyldiethylarsenite 2. © 1997 John Wiley & Sons, Inc.
Asymmetric Michael addition of 2‐nitropropane to a chalcone catalyzed by chiral crown ethers incorporating a D‐glucose unitBakó, Péter; Töke, László; Szöllösy, Áron; Bombicz, Petra
doi: 10.1002/(SICI)1098-1071(1997)8:4<333::AID-HC8>3.0.CO;2-Bpmid: N/A
Michael addition of 2‐nitropropane 4 to a chalcone 3 catalyzed by crown ethers incorporating two glucose units (of 1 type) afforded the adduct 5 with an R‐enantiomer excess (28% ee) while the aza‐crown ethers containing one glucose unit (of 2 type) gave the same adduct favoring the S‐enantiomer under solid–liquid phase transfer conditions (SL‐PT). It was proven that substituents at the N‐atom of the crown ring in 2 have a significant effect on both the chemical yield and the enantioselectivity, and those having heteroatoms in the proper position of the side chain (2e, 2f) showed the best results in this reaction: 65% ee for the S‐antipode. The absolute configuration of (+)‐4‐methyl‐4‐nitro‐1,3‐diphenyl‐1‐pentanone (5), determined by X‐ray diffraction, is also presented in this article. © 1997 John Wiley & Sons, Inc.
1,2λ5,5λ5‐azadiphospholium structuresSchmidpeter, Alfred; Polborn, Kurt
doi: 10.1002/(SICI)1098-1071(1997)8:4<347::AID-HC10>3.0.CO;2-Rpmid: N/A
The reactions of bromophenylacetylene with the diphenylphosphino amines (Ph2P)2NH and (Ph2P)3N result in the 1,1,3,3,4‐pentaphenyl‐1,2,5‐azadiphospholium bromide (5) and its 4‐diphenylphosphino derivative (7). Their X‐ray structure analyses show planar rings for the cations. The small endocyclic angle at the nitrogen ring member is associated with PN bonds that are longer than in the acyclic cation (Ph3P)2N+. The data fit to a negative linear relationship of PN bond lengths and PNP bond angles. © 1997 John Wiley & Sons, Inc.