Band 20, Heft 4

A novel protocol for the synthesis of 11-substituted dibenzo[ b , f ][1,4]oxazepines is reported. Seven compounds were designed as analogs of the antipsychotic drug loxapine and antidepressant amoxapine. The key transformations include generation of a carbamate intermediate using phenyl chloroformate which avoids the use of harmful phosgene, a microwave-induced transformation of the carbamate intermediate into various urea derivatives, and a subsequent phosphorous oxychloride-induced cyclocondensation. The simple reactions and wide substrate scope enhance the practical application of this methodology.

The N -tosylaziridine 4 of (+)-2-carene 1 was prepared and subjected to solvolytic reactions with weak protic acids. For comparison, the solvolytic reactions of cis -3-carene- N -tosylaziridine 8 were also studied. The solvolyses of 4 were more rapid than those of 8 , and both rings were opened in 4 , whereas only the aziridine was opened in 8 . This leads to the conclusion that the aziridine and cyclopropane rings in 4 can achieve a conjugated transition state.

Two new asymmetrical 3-( p -R-phenyl)-4-amino-5-(2-pyridyl)-1,2,4-triazoles ( 3a , R = CH 3 and 3b , R = OCH 3 ) were synthesized with a yield of 58% and 69%, respectively. The compounds 3a and 3b were characterized with FT-IR, 1 H NMR, ESI-MS spectra, and elemental analysis. Additionally, their molecular and crystal structures were determined by single crystal X-ray analysis.

Abstract: A tandem strategy for the synthesis of 7,12-dihydro-1,3,6,7,12-pentaazapleiadenes and 4-(2-aminophenoxy)pyrido[4,3- d ]pyrimidin-5(6 H )-ones from readily available starting materials has been developed.

The electronic structure and prototropic tautomerism of 4,6-dimethylisoxazolo[3,4- b ]pyridin-3(1 H )-one ( 1 ) were studied theoretically with use of the B3LYP/6-31G* and ωB97X-D/6-31G* density functional methods and SM8 (H 2 O, DMF) solvation models. Compound 1 , which is a weak acid with a p K a of 6.9, undergoes regioselective alkylation and sulfonylation under basic reaction conditions to give a series of N 1-substituted products 2a – i . Later compounds were evaluated in vitro for antibacterial activity with the use of 68 strains of aerobic and anaerobic bacteria, including 12 reference strains.

A series of novel purine based N -acyl- α -carboxamides were prepared via the Ugi four-component reaction approach using the pharmacophoric 2-amino-6-chloropurine moiety as the amine component coupled with various aldehydes, carboxylic acids and isocyanides affording a library of multisubstituted compounds 2a–x . These compounds were screened for their antimicrobial activity against Gram negative strains Escherichia coli , Pseudomonas aeruginosa and Gram positive strains Staphylococcus aureus , Staphylococcus epidermidis demonstrating significant biological potency. The best potency for all the strains was found for compound 2x , which is comparable with ampicillin trihydrate as the standard drug.

A short two-step synthesis of substituted dihydro-1 H -pyrazolo[3,4- d ]thiazoles from 4-thiazolidinones is described. 4-Thiazolidinones are easily synthesized by the reaction of thiosemicarbazones of carbonyl compounds and chloroacetic acid. Upon treatment with Lawesson’s reagent and dimethylformamide-dimethylacetal, 5-dimethylaminomethylene-3-methylthiazolidine-4-thiones are formed, which undergo condensation with hydrazine derivatives to furnish substituted dihydro-1 H -pyrazolo[3,4- d ]thiazoles. The structure of the synthesized compounds was established by elemental analysis and analysis of spectral data.

The reaction of thiocarbohydrazide with benzil and a substituted phenacyl bromide provides a facile synthetic route to a 1,2-diphenyl-2-[2-(5-aryl-6 H -1,3,4-thiadiazin-2-yl)hydrazono]ethanone. The synthesized compounds were characterized by spectral and analytical data.

(CH 3 ) 2 Ge=Si: and its derivatives (X 2 Ge=Si:, X=H, F, Cl, Br, Ph, Ar) are a new species. Their cycloaddition reaction is a new area for the study of silylene chemistry. The mechanism of the cycloaddition reaction between singlet (CH 3 ) 2 Ge=Si: and formaldehyde was investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the reaction has one dominant pathway. The reaction rule presented is that the two reactants first form a four-membered Ge-heterocyclic silylene through the [2+2] cycloaddition reaction. Because of the 3p unoccupied orbital of Si: atom in the four-membered Ge-heterocyclic silylene and the π orbital of formaldehyde forming a π→p donor-acceptor bond, the four-membered Ge-heterocyclic silylene further combines with formaldehyde to form an intermediate product. The Si: atom in the intermediate product is sp 3 hybridized after transition state, and this intermediate isomerizes to a spiro-Si-heterocyclic compound involving Ge via a transition state.