No abstract

2-Thiohydantoin derivatives are produced by heating a mixture of thiourea and an α-amino acid. The method described offers the advantages of simplicity, low cost, easy work-up and scalability.

A new reaction between 2‐aminobenzophenone and thiourea in dimethyl sulfoxide (DMSO) has been developed that primarily affords 4‐phenylquinazoline as a single product. This reaction is also applicable, in general, to the reactions between thiourea and conformation‐restricted β‐amino ketones, such as 1‐aminoanthracene‐9,10‐dione and 1‐amino‐9H‐fluoren‐9‐one, to prepare perimidine derivatives. Experimental data is consistent with our computational study on the thermal decomposition of thiourea to form hydrogen sulfide and carbodiimide. This reaction involves a coupling between 2‐aminobenzophenone and carbodiimide generated in situ from thiourea to form 4‐phenylquinazolin‐2(1H)‐imine intermediate, and the generation of sulfur‐containing reducing agent from hydrogen sulfide and DMSO, which reduces 4‐phenylquinazolin‐2(1H)‐imine to 4‐phenyl‐1,2‐dihydroquinazolin‐2‐amine. Elimination of ammonia from the latter yields 4‐phenylquinazoline.

A benchmark comparison for different computational methods and basis sets has been presented. In this study, five computational methods (Hartree-Fock (HF), MP2, B3LYP, MPW1MP91, and PBE1PBE) along with 18 basis sets have been applied to optimize the geometry of carbon disulfide (CS 2 ), and further calculate the vibrational frequencies of the optimized geometries. The differences between the calculated frequencies and corresponding experimental data are used to evaluate the efficiency of each combination of computational method and basis set. The comparison of frequency difference indicates that B3LYP generally gives the best prediction of frequencies for CS 2 , whereas the other two density functional theory (DFT) methods, i.e., MPW1PW91 and PBE1PBE, often give parallel results. Although MP2 predicts the frequencies with accuracy almost as good as those from DFT methods, in a particular case, HF calculation outperforms MP2 as well as MPW1PW91 and PBE1PBE for prediction of the frequency of asymmetrical stretching for CS 2 .

A simple and convenient method for the preparation of fully acetylated and (3-bromo)benzoylated α-monosaccharides and disaccharides through vigorous mechanical mixing of solid reactants on a high speed shaker is described. Using this technique a variety of α‑acylated sugars are prepared, including penta-O-acetyl-α-D-galactopyranose, penta-O-acetyl-α-D-glucopyranose, penta-O-acetyl-α-D-mannopyranose, octa-O-acetyl-α-lactose, penta-O-(3-bromo)benzoyl-α-D-galactopyranose, penta-O-(3-bromo)benzoyl-α-D-gluco-pyranose, penta-O-(3-bromo)benzoyl-α-D-mannopyranose, and octa-O-(3-bromo)benzoyl-α-lactose.