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Synthesis of 3,4-dihydro-2H-1,4-oxazines
Recent Literature
Aziridines react with propargyl alcohols in the presence of Zn(OTf)2
as the Lewis acid catalyst, following an SN2-type ring-opening
mechanism to furnish the corresponding amino ether derivatives. In the presence
of Zn(OTf)2 and tetrabutylammonium triflate salt, those amino ethers
further undergo intramolecular hydroamination via 6-exo-dig
cyclization to provide 3,4-dihydro-2H-1,4-oxazine products.
B. Singh, M. Kumar, G. Goswami, I. Verma, M. K. Ghorai, J. Org. Chem., 2023, 88,
4504-4518.
A Rh(II)-catalyzed reaction between 1-tosyl-1,2,3-triazoles and halohydrins
provides 2,6-substituted 3,4-dihydro-2H-1,4-oxazines under basic
conditions. The reaction is proposed to undergo a rhodium carbenoid
1,3-insertion into O-H followed by an annulation.
K. D. Jones, M. J. Nutt, E. Comninos, A. N. Sobolev, S. A. Moggach, T. Miura,
M. Murakami, S. G. Stewart,
Org. Lett., 2020, 22, 3490-3494.
A solvent- and metal-free regioselective cyclization affords 1,4-oxazine and
1,4-oxazepine derivatives as exo-dig products. Substrates for the
cyclization step can be produced in a highly diastereomeric fashion by Grignard
reaction as key synthetic step following Cram’s rule.
J. K. Vandavasi, W.-P. Hu, H.-Y. Chen, G. C. Senadi, C.-Y. Chen, J.-J. Wang, Org. Lett., 2012,
14, 3134-3137.