1H and 13C spectral assignment of substituted 5H-[1,3]thiazolo[2,3-b]quinazolin-5-one and 12H-[1,3]benzothiazolo[2,3-b] quinazolin-12-one

(1)H and (13)C spectroscopic data for 5H-[1,3]thiazolo[2,3-b]quinazolin-5-one and 12H-[1,3]benzothiazolo[2,3-b]quinazolin-12-one derivatives were fully assigned by combination of one- and two-dimensional experiments (DEPT, HMBC and HMQC). Both heterocyclic systems show similar spectroscopic properties with some remarkable differences.     

Conformational analysis of some 11, 12-dihydrodibenz[B,F][1, 5]oxazocin-6-one derivatives by NMR spectroscopy

A variable temperature 200 MHz ¹H NMR investigation of some N-acylsubstituted 11, 12-dihydrodibenz[b, f][1, 5]oxazocin-6-ones showed the presence at room temperature of at least two conformationally restricted diastereomers (and their enantiomers) which molecular mechanics calculations strongly suggested to be a boat-like structure (major conformer) and a pseudo-chair and/or twistboat-like structure (minor conformer). The diastereomersinterconvert through a bond rotation mechanism just above room temperature (51-54°C, depending upon the nature of the N-acyl substituent), and the boat enantiomers interconvert at higher temperatures (75-95°C, depending upon the nature of the N-acyl substituent and the substitution pattern of the aromatic rings) via a ring inversion process. The N-acyl groups exocyclic to the eight-membered ring are shown to wholly exist - probably as a result of severe dipole: dipole interactions - in the sterically disfavoured conformation where the alkyl substituent bonded to the exocyclic carbonyl carbon atom is trans to the benzylic methylene group. Corresponding N-unsubstituted derivatives exhibit rapid ring inversion on the NMR time scale at room temperature.     

Phase transfer catalysis in N-alkylations of the pharmaceutical intermediates 5H-dibenz[b,f]azepine and 5H-10,11-dihydrodibenz[b,f]azepine

The two title compounds were alkylated under very mild phase-transfer-catalysis conditions. Differences in reactivities of the two heterocyclic nucleophiles, and in the reactivities of various alkyl halides are discussed.     

Synthesis of 2-Phenyl-3-oxa-5-azatricyclo[4.4.0.02 , 7]decan-4-one

Cleavage of the lactone ring in 7-phenylbicyclo[3.1.1]heptan-6,7-carbolactone by the action of ammonia and hydrazine and subsequent oxidative cyclization of the resulting hydroxy amide and hydroxy hydrazide gave a cyclic carbamate, 3-oxa-5-azatricyclo[4.4.0.0^{2 , 7}]decan-4-one.     

Dibenz [b,f]-1, 4-oxazepin-11 (10 H)-one und Dibenz [b,e]-1, 4-oxazepin-11 (5 H)-one. 12. Mitteilung über siebengliedrige Heterocyclen

The syntheses of dibenzo [b, f]-1, 4-oxazepin-11 (10 H)-ones (I) with electron-attracting substituents in position 2 by ring closure of the sodium salts of 2-halogeno-2′-hydroxy-benzanilides (II) are described. The reaction of II (R = SO₂·N(CH₃)₂) in N-methylpyrrolidone also led, by SMILES rearrangement, to the isomeric minor product dibenzo [b, e]-1, 4-oxazepin-11 (5 H)-one (III; R = SO₂·N(CH₃)₂), whose constitution was proven by synthesis from VI. In the case of II (R = SO₂·CH₃), the 5-methylsulfonyl-2-(2-hydroxyanilino)-benzoic acid (VI; R = SO₂·CH₃) was obtained directly after hydrolysis. The lactam I (R = NO₂) was rearranged to the corresponding acid VI by heating with dilute caustic soda.     

Synthesis and properties of 172-phenyl-5,10,15,20-tetraazatribenzo[b,g,l]pyrazino[2,3-q]porphyrin-173(174 H)-one

17²-Phenyl-5,10,15,20-tetraazatribenzo[b,g,l]pyrazino[2,3-q]porphyrin-17³(17⁴ H)-one was synthesized for the first time by template cyclotetramerization of 5,7-diphenyl-6H-1,4-diazepine-2,3-dicarbonitrile with phthalonitrile. Its complexation with zinc(II) acetate followed a bimolecular mechanism. Acid-base properties of the resulting zinc complex in benzene-acetic acid were studied, and the stability constant of its monoprotonated (at the meso-nitrogen atom) form was determined.     

Distinct difference of chemical behaviors between 5H,7H-dibenzo[b,g][1,5]dithiocin 12-oxide and thiazocine S-oxide

5H, 7H-Diobenzo [b,g] [1,5] dithiocin 12-oxide (2) rearranged into 6-oxide (3) in the presence of CF₃CO₂H. The corresponding thiazocine S-oxide (5) was only protonated at the amino group under the same conditions. Furthermore, methylation of 2 afforded S-methylated product (7) in contrast to O-methylated product in 5.