27025-90-7Relevant articles and documents
Metal-Catalyzed Isomerization of 5-Heteroatom-Substituted Isoxazoles as a New Route to 2-Halo-2 H -azirines
Rostovskii, Nikolai V.,Agafonova, Anastasiya V.,Smetanin, Ilia A.,Novikov, Mikhail S.,Khlebnikov, Alexander F.,Ruvinskaya, Julia O.,Starova, Galina L.
, p. 4478 - 4488 (2017)
A convenient gram-scale method for the preparation of 2-halo-2 H -azirine-2-carboxylic acid esters, thioesters and amides via metal-catalyzed isomerization of 5-heteroatom-substituted 4-haloisoxazoles is developed. The formation of the esters and amides is efficiently catalyzed by Rh 2 (Piv) 4, while FeCl 2 ·4H 2 O is the catalyst of choice for the synthesis of the thioesters. In addition, rhodium catalysis is successfully applied in the synthesis of azirine-2-carboxylates from non-halogenated 5-alkoxyisoxazoles.
Switchable Synthesis of Pyrroles and Pyrazines via Rh(II)-Catalyzed Reaction of 1,2,3-Triazoles with Isoxazoles: Experimental and DFT Evidence for the 1,4-Diazahexatriene Intermediate
Rostovskii, Nikolai V.,Ruvinskaya, Julia O.,Novikov, Mikhail S.,Khlebnikov, Alexander F.,Smetanin, Ilia A.,Agafonova, Anastasiya V.
, p. 256 - 268 (2017/04/26)
4-Aminopyrrole-3-carboxylates and pyrazine-2-carboxylates were synthesized from 5-alkoxyisoxazoles and 1-sulfonyl-1,2,3-triazoles by tuning the Rh(II) catalyst and the reaction conditions. The reaction in chloroform at 100 °C under Rh2(OAc)4 catalysis provides 4-aminopyrrole-3-carboxylates in good yields. The use of Rh2(Piv)4 in refluxing toluene results in the formation of 1,2-dihydropyrazine-2-carboxylates as the main products, which can be converted by a one-pot procedure to pyrazine-2-carboxylates by heating with catalytic amounts of TsOH. According to the NMR and DFT investigations of the reaction mechanism, pyrroles and dihydropyrazines are formed, respectively, via 1,5- and 1,6-cyclization of common (5Z)-1,4-diazahexa-1,3,5-triene intermediates. The influence of the nature of the catalyst on the product distribution is rationalized in terms of the Rh-catalyzed isomerization of a pyrrolin-2-ylium-3-aminide zwitterion, the primary product of 1,4-diazahexatriene 1,5-cyclization.
