Q2. What is the ring in molecule B?
The heterocyclic ring in molecule B also has an envelope conformation, but is more distorted from ideal geometry than the ring in molecule A and a different ring atom – C(25) – forms the envelope flap.
Q3. What is the NH group in molecule A?
The NH group in molecule A forms an intermolecular hydrogen bond with the imine N-atom of a neighboring mole-© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org Eur. J. Org. Chem. 2005, 3128–31373130cule B.
Q4. How did the formation of selenazoles occur?
The formation of 1H-1,3,6-triazaaceanthrylene derivatives 5 occurred on heating of 1 and 4 in boiling pyridine without any additional reagents.
Q5. What is the chemical structure of the aryl isoselenocyanates?
The authors have recently shown that aryl isoselenocyanates 1 are convenient precursors for the introduction of selenium into five- and six-membered selenaheterocycles of types 3[50] and 5,[51] respectively (Scheme 1).
Q6. What is the reaction mechanism for the formation of 9 and 10?
The authors propose the following reaction mechanism for the formation of 9 and 10: addition of the primary amino group to 6 produces a selenourea derivative A, which undergoes a cyclization step to give the heterocyclic product.
Q7. What is the phenyl group in the envelope?
The heterocyclic ring in the major conformation has a slightly distorted half-chair conformation twisted on C(4a)–C(5a), with the distortion being in the direction of an envelope with C(5a) as the envelope flap.
Q8. What is the symmetry of the methylene groups in the heterocyclic ring?
In the case of 9d, the methylene groups in the heterocyclic ring are disordered over two conformations, with the major conformation occurring in approximately 70% of the molecules.
Q9. What was the way to obtain the free amine derivative?
In the latter case, however, the product was obtained as the hydrochloride, which was very stable and gave the free amine derivative only with difficulty.
Q10. What are the main characteristics of the compounds?
Although syntheses of thiazines[27] and oxazines[28,29] are well known, those of the corresponding selenazines have been limited, owing to difficulties in the preparation of the selenium-containing starting materials.
Q11. what is the chemical and spectroscopic structure of all new compounds?
Chemical and spectroscopic evi-dence for the structures of all new compounds are presented,The chemistry of organoselenium compounds has attracted much attention, not only because of strong interest in these compounds as synthetic tools[1–8] but also as a result of their unique biological[9,10] and medicinal activities.
Q12. What is the first equivalent of the base needed to generate the free amine in situ?
The first equivalent of the base is needed to generate the free amine in situ, and the second to capture HX formed during the cyclization step.
Q13. What is the role of selenazoles in the chemistry of dyestuff?
selenazoles have attracted attention in the chemistry of dye-stuffs,[41,42] as well as in medicine (antiinfective,[36] antiviral,[43] and antitumor agents[44]).