A stereocontrolled route to protected isocyanates from alcohols

Full details are given for a modified Mitsunobu approach to the formation of N-alkylated 1,2,4-dithiazolidine-3,5-diones 2 from a wide range of alcohols 10 with predominantly, inversion of configuration. The resulting products 2 can be regarded as protected isocyanates 6.     

Highly stereoselective De-Novo synthesis of protected 2-amino-3-C-methyl-2,3-dideoxy-d-altrose

A new strategy for the stereoselective synthesis of 2-amino-2-deoxy-aldoses is described. Therefore epoxy carbamates are reacted with isocyanates to furnish urethanes, which will form the title compounds with high diastereoselectivities under basic conditions and O,O-migration of the carbamoyl group.     

A novel class of compounds: synthesis of 5,5′-carbonyl-bis(5,6-dihydro-4H-furo- and thieno-[2,3-c]pyrrol-4-ones)

We hereby report the first synthesis of novel class of compounds, 5,5′-carbonyl-bis(5,6-dihydro-4H-thieno- and furo-[2,3-c]pyrrol-4-one starting from methyl 2-(2-methoxy-2-oxoethyl) thiophene- and furan-3-carboxylate, respectively. The ester functionalities connected to methylene group were regiospecifically converted to the desired monoacyl azides. Curtius rearrangement of acyl azides followed by hydrolysis of the formed isocyanates gave the symmetrical urea derivatives. Cyclization of the ester groups provided the target compounds.     

Amide bands in the IR spectra of urethanes

The objective of this article is investigation of the normal modes of vibrations of molecules containing amide or urethane groups. Comparison between methyl-N-methylcarbamate (MMC) and N-methylacetamide (NMA) has been discussed. Density functional (DFT) calculations at B3LYP/6-31G(d) level have been employed to investigate the normal modes of MMC and several simple urethanes. This level was used as a compromise between accuracy and applicability to larger systems. The obtained results are in good agreement with experimental spectra. Finally, we have confirmed that the use of “amide terminology” is correct when addressing urethane molecules.     

Herbizide Thienylharnstoffe,I

Summary Syntheses of the title substances as potential herbicides are described by a modified Curtius degradation of corresponding thiophene carboxylic acids, obtained in turn by haloform reaction of appropriate acetyl thiophenes. Regioselective substitution reactions of thiophenes were key steps for the construction of desired substitution patterns. Structure—activity considerations show that especially the 3-thienyl ureas36 and38 exhibit significant herbicidal activity comparable with commercial products.