ChemInform Abstract: R*R* AND R*S* α‐ETHYLENIC AZIRIDINES: CHARACTERISTICS AND SPONTANEOUS REARRANGEMENTS

Abstract

Einwirkung von Ph3P auf die Vinylaminoalkohole (Ia)‐(Ih) liefert unter den angegebenen Bedingungen unter Konfigurationsinversion die Aziridine (IIa)‐(IIh).

Rearrangement of N‐Aryl‐2‐Vinylaziridines to Benzoazepines and Dihydropyrroles: A Synthetic and Theoretical Study

“…Calculations identified the key role of the effects of the substituents on the relative stabilities of the starting N-aryl-2-vinylaziridine conformations allowing us to give a rationale of the experimentally observed chemoselectivity of the rearrangement to N-heterocyclic compounds. It should be pointed out that our study allows us to rationalize the aza-[3,3]-Claisen rearrangement of N-aryl-2-vinylaziridines to benzoazepines, a reaction already mentioned in the literature several years ago, [32][33][34] but never applied in a systematic way. In conclusion, we believe that this synthetic study, accompanied by a theoretical investigation, has allowed us to turn some isolated observations into an efficient and predictable synthetic methodology.…”

“…These last products are formed by [3,3]-Claisen rearrangements of the corresponding N-aryl-2-vinylaziridines. Although, this reaction has been known since 1967, [32][33][34] up to now its scope was not deeply investigated in spite of the scientific interest in developing new methodologies to afford benzoazepine derivatives [11,[35][36][37][38] for their pharmaceutical activity in several psycho-diseases. [39][40][41][42] It should be noted that the limited literature on this subject is probably due to the great chemical instability of N-aryl-2-vinyl-A C H T U N G T R E N N U N G aziridines that prevents their extensive use as starting materials.…”

The [Ru(CO)(porphyrin)]‐Catalyzed Synthesis of N‐Aryl‐2‐vinylaziridines

“…We propose that the formation of 7 could be due to rearrangement of the initially formed N-aryl-2-vinylaziridine, which should be more prone to this kind of reaction than the corresponding N-tosyl-2-vinylaziridine (Scheme 2). [36,37] Scheme 2.…”

“…Note that under these experimental conditions we observed the presence of the byproduct 2,5-1H-benzo[b]azepine (8), formed by an aza- [3,3]-Claisen rearrangement of the 2-vinylaziridine. [5,13,36,37] To avoid the formation of benzoazepines and to obtain 2-vinylaziridines in good yields, the reaction must be run for no longer than the time necessary for the consumption of the azide. The crude product must be purified rapidly and the purified product must be stored at Յ 4°C.…”

“…The chemical stability of a vinylaziridine largely depends on the nature of the substituent on its aziridine nitrogen, [32][33][34][35] with reactivity towards nucleophiles being promoted by the presence of an electron-withdrawing group on the nitrogen atom [3,34] whereas a rearrangement frequently occurs when a N-aryl group is present in the molecule. [36,37] Organic azides [38] -in particular sulfonyl [39,40] and aryl azides [41,42] -represent a versatile class of aminating agents. They can be regarded as atom-efficient nitrogen atom transfer agents because their decomposition generates the nitrene functionality and molecular nitrogen as the only side product.…”