Radioprotective action of thiadiazole derivatives
Continuing previous investigations on the search for radioprotectors among the sulfurcontaining heterocycles [i, 2], we synthesized and studied the radioprotective properties of derivatives of 1,3,4and 1,2,4-thiadiazoles with various substituents: amino groups, alkyls, and mercapto groups. The following thiadiazole derivatives were investigated: 2alkylamino-5-alkyl-l,3,4-thiadiazoles and their methiodides (I-VII); 2-alkylamino-l,3,4thiadiazole-5-thiones (VIII-XII); 2-alkylamino-5-alkylmercapto-l,3,4-thiadiazoles (XIIIXVIII); 2,5-diamino-l,3,4-thiadiazole and its methiodide (XIX, XX), and 1,2,4-thiadiazoles (XXI-XXIII).
Über 1.2.4‐Thiodiazole, VII. Mitteil.: Herstellung von 3‐Alkylmercapto‐5‐amino‐1.2.4‐thiodiazolen aus Alkylisothioharnstoffen (Mitbearbeitet von Walter Zengerling)
Eine Reihe von Alkylisothioharnstoffen und Phenylisothioharnstoff wurden mit Rhodanid, Brom und Alkali in die 3-Alkylmercapto-5-amino-1.2.4-thiodiazole ubergefuhrt. Die Reaktion ist allgemein anwendbar und verlauft mit guter Ausbeute. Eigenschaften und einige Derivate der neuen heteroaromatischen Amine werden beschrieben.
Enantioselective Synthesis of Dihydropyrans. Catalysis of Hetero Diels−Alder Reactions by Bis(oxazoline) Copper(II) Complexes
C2-symmetric bis(oxazoline)−Cu(II) complexes 1 and 2 catalyze the inverse electron demand hetero Diels−Alder reaction of α,β-unsaturated carbonyl compounds (heterodiene) with electron-rich olefins (heterodienophile) in high diastereo- and enantioselectivity. α,β-Unsaturated acyl phosphonates and β,γ-unsaturated α-keto esters and amides are effective heterodienes, while enol ethers and sulfides function as heterodienophiles. A range of substitution patterns is possible on the heterodiene:  terminal alkyl, aryl, alkoxy, and thioether substituents are all tolerated. The enantioselective synthesis of dihydropyrans by this method has been shown to be straightforward:  cycloadditions may be conducted with as little as 0.2 mol % of the chiral catalyst and are readily run on multigram scale. The reactions exhibit a favorable temperature−enantioselectivity profile, with selectivities exceeding 90% even at room temperature. A simple reaction protocol that employs a solid air-stable catalyst, convenient reaction tem...