Oxidative addition ofN-aminophthalimide to conjugated azoalkenes. Synthesis of the first C-azoaziridines

The oxidation ofN-aminophthalimide with lead tetraacetate in the presence of \-phenylazostyrene or 1-phenylazocyclohexene results in phenylazo-1-phthalimidoaziridines, the first among derivatives of C-azoaziridines. 1-Phenylazopentene yields quite different product, 2-phenyl-2,4,5,6-tetrahydrocyclopenta[d]-1,2,3-triazole. From 2-phenylazapropene was obtained a mixture of the corresponding triazole andN- [2-(phenylhydrazono)propylidenamino]phthalimide, but the same reaction with the cyclic azoalkene, 3,3,5-trimethyl-3H-pyrazole, afforded the mixture of three regio and stereoisomeric phthalimidoazimines.     

Conjugated azoalkenes. Part V. Facile synthesis of new 1-aroylamino-3-sulfonylpyrroles by reaction of aroylazoalkenes with 1,3-ketosulfones

The easy one-pot synthesis of the interesting 1-aroylamino-3-sulfonylpyrroles by reaction of some aroylazo-alkenes with 1,3-ketosulfones is reported.     

Enantioselective synthesis of dihydropyrazoles by formal [4+1] cycloaddition of in situ-derived azoalkenes and sulfur ylides

An unprecedented strategy to access highly enantioenriched dihydropyrazoles is described. It involves formal [4+1] cycloadditions of in situ-derived azoalkenes and sulfur ylides catalyzed by a chiral copper/Tol-BINAP complex. A variety of synthetically and biologically important dihydropyrazoles have been obtained with high enantioselectivities (up to 97:3 er) in good yields (83-97%).     

A new method for the generation of azoalkenes from ketohydrazones and its application to the synthesis of tetrahydropyridazine derivatives

The reaction of ketohydrazones containing an α-methylene group with chloramine-T followed by treatment with triethylamine leads to the formation of azoalkenes via an α-chloroazo-compound, which can react intermolecularly and in situ with olefinic compounds to produce tetrahydropyridazine derivatives in good yield.     

Effect of metal ions in organic synthesis. Part XXXI. Synthesis of new 3-carbonyl- and 3-carboxy-1-heterocyclaminopyrroles by copper(II) chloride-catalyzed reaction of heterocyclic azoalkenes

The direct synthesis of a new class of unknown 1-heterocyclamino-3-carbonylpyrroles and 1-heterocyclamino-3-carboxypyrroles by copper(II) chloride-catalyzed reaction of heterocyclic conjugated azoalkene derivatives with β-diketones and β-ketoesters is reported.     

Experimental and theoretical insights regarding the cycloaddition reaction of carbohydrate-based 1,2-diaza-1,3-butadienes and acrylonitrile. A model case for the behavior of chiral azoalkenes and unsymmetric olefins

A series of carbohydrate-based tetrahydropyridazines are prepared by the hetero-Diels-Alder reaction of the chiral 1,2-diaza-1,3-butadienes 1 and 2 with acrylonitrile. Reactions are regiospecific, and the observed diastereoselection is consistent with a preferred attack to the Re face of the heterodiene unit, as the chiral sugar placed at C4 does largely protect the opposite Si face. The stereochemistry of the major cycloadduct 4 has been firmly established by an X-ray crystallographic study that, in addition, reveals a conformation placing the cyano group in axial orientation. Cycloadducts such as 9 and 11, in which the axial cyano group and the carbohydrate moiety exhibit a cis relationship, undergo a facile E2 elimination that relieves the steric congestion. A detailed computational study is reported to provide better insight into the factors that influence this asymmetric cycloaddition. A DFT study (B3LYP/6-31G) on a reduced model does correctly predict the regiochemistry observed experimentally, while the facial diastereoselection is modeled at a semiempirical (PM3) level on the parent reagents, thereby accounting for the steric factor provided by the chiral substituent. The calculations also indicate that the axial orientation of the cyano group can be rationalized in terms of a stabilizing anomeric effect.     

[4 + 1] Annulation of in situ generated azoalkenes with amines: A powerful approach to access 1-substituted 1,2,3-triazoles

1-Substituted 1,2,3-triazoles represents ‘privileged’ structural scaffolds of many clinical pharmaceuticals. However, the traditional methods for their preparation mainly rely on thermal [3 + 2] cycloaddition of potentially dangerous acetylene and azides. Here we report a base-mediated [4 + 1] annulation of azoalkenes generated in situ from readily available difluoroacetaldehyde N-tosylhydrazones (DFHZ-Ts) with amines under relatively mild conditions. This azide- and acetylene-free strategy provides facile access to diverse 1-substituted 1,2,3-triazole derivatives in high yield in a regiospecific manner. This transformation has great functional group tolerance and can suit a broad substrate scope. Furthermore, the application of this novel methodology in the gram-scale synthesis of an antibiotic drug PH-027 and in the late-stage derivatization of several bioactive small molecules and clinical drugs demonstrated its generality, practicability and applicability.     

Herrn Professor Dr. Dr. h. c. mult. J. F. K. Huber

Ohne Zusammenfassung     

Ein Teleskop-Brenner. D.R.G.M.

Ohne Zusammenfassung     

Gaspolarographie. II. Mitt.

Zusammenfassung Stickstoffdioxid, Stickstoffmonoxid, Distickstofftrioxid und Distickstoffmonoxid sind in wasserfreiem Dimethylsulfoxid polarographisch erfaßbar.

---

Summary Nitrogen dioxide, nitrogen, monoxide, nitrogen trioxide, and nitrous oxide can be detected polarographically in anhydrous dimethylsulfoxide.

---

Résumé On peut déceler le peroxyde d'azote, l'oxyde azotique, l'anhydride azoteux et l'oxyde azoteux par polarographie dans le diméthylsulfoxyde anhydre.

---

---

Herrn Prof. Dr.A. A. Benedetti-Pichler zum 70. Geburtstag gewidmet.

---

Für die Unterstiitzung der Untersuehungen wird der Regierung der USA gedankt.     

Prof. Dr. Dr. h. c. Fritz Feigl zum 70. Geburtstag

Ohne Zusammenfassung