Ortho-dialkylaminoarylidene malonates undergo hydrogen transfer mediated cyclization in absence of catalyst under LED irradiation. Such activation mode is found to be relatively general and could be applied to a number...
Benzylidene imidazolones with ortho-secondary aminogroup undergo acid-promoted chemodivergent spirocyclization. Strong Lewis acids provide access to spirocyclic tetrahydroquinolines via [1,5]hydride shift triggered cyclization despite of the presence of free secondary amino group. Brønsted acids promote unprecedented intramolecular umpolung hydroamination reaction with the formation of spirocyclic indolines. Each of the processes proceeds with exclusive atom-economy.
A new general approach for the synthesis of azolo [4,5b]quinolines via dealkylative TiCl 4 -mediated cyclization of 2dialkylamino-arylidene-azol-ones upon heating in dichloroethane is found. The reaction scope and limitations are established, showing that at least two different heterocyclic cores could be obtained. Dozen products were obtained in moderate to good yields (22-64 %).
A new simple one-pot two-step protocol for the synthesis of 2-oxo-1,2,3,4-tetrahydroquinoline-3-carboxylate from 2-(2-(benzylamino)benzylidene)malonate under the action of BF3·Et2O was developed. It was shown that the reaction proceeds through the formation of a stable iminium intermediate containing a difluoroboryl bridge in the dicarbonyl fragment of the molecule.
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