Alves, M. José

Duarte, Vera C. M.

Faustino, H.

Fortes, A. Gil

Salgueiro, D. A. L.

Universidade do Minho: RepositoriUM

ASYMMETRIC DIELS-ALDER REACTION OF tert-BUTYL 2H-AZIRINE-3-CARBOXYLATE BY A SELF-ASSEMBLED COMPLEX OF BINOL, Mg AND Zn  Duarte, V. C. M.; Faustino, H.; Salgueiro, D. A. L.; Gil Fortes, A.; Alves, M. J.  Centro de Química, Universidade do Minho, Campus de Gualtar 4710-057 Braga, Portugal; vera10@sapo.pt   In the past the reaction of tert-butyl 2H-azirine-3-carboxylate (1) with 1,3-butadienes containing a glucosyl moiety as chiral auxiliary showed complete facial selectivity.[1] However, the reaction of erythrose diene 2 with the same azirine 1 proceeds with low selectivity giving a 2.5:1 mixture of compounds 3 and 4. In an attempt to overcome this lack of selectivity the reaction components were tethered in a LACASA-Diels-Alder cycloaddition (LACASA-DA) using a bimetallic complex of Mg(II) and Zn(II) having R-/S-BINOL as chiral ligand. This method had been first developed by Inomata in reaction of dienol with nitroso dienophiles, in the presence of tartaric acid-zinc complex.[2] Later Ward reported a highly enantioselective LACASA-DA reaction of diene 5 with methyl acrylate. [3]  Bearing in mind the result obtained by Ward, we combined the same diene (5) with azirine 1. The reaction proceeded at low temperature giving homochiral compound 6 in two diastereomeric forms depending on the stereochemistry of BINOL chiral inductor (R/S). Application of this methodology to reaction of chiral diene 2 with azirine 1 also gave complete facial control affording products 3 or 4 according to the BINOL chiral ligand. Non-optimized yields of products ranged from 30-50 %.  [1] Alves, M. J.; Gilchrist, T. L. Tetrahedron Lett., 1998, 39, 7579-7582. [2] a) Ding, X.; Ukaji, Y.; Fujinami, S.; Inomata, K. Chem. Lett., 2003, 32, 582-583. b) Ukaji, Y.; Inomata, K. Synlett, 2003, 1075-1087. [3] a) Ward, D. E.; Souweha; M. S. Org. Lett., 2005, 3533-3536. b) Ward, D. E.; Mohammad; S. A. Org. Lett., 2000, 3937-3940.  Acknowledgements We thank FCT for project funding PTDC/QUI/67407/2006; FCT and FEDER for funding NMR spectrometer Bruker Avance III 400 as part of the National NMR Network RNRMN; V.C.M.D. also thanks for PhD grant (SFRH/BD/61290/2009).  

Asymmetric diels-alder reaction of tert-butyl 2H-azirine-3-carboxylate by a  self-assembled complex of binol, mg and zn

http://repositorium.sdum.uminho.pt/bitstream/1822/22054/3/Vera_abstract_6SPJOCS.pdf

Asymmetric diels-alder reaction of tert-butyl 2H-azirine-3-carboxylate by a self-assembled complex of binol, mg and zn

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Universidade do Minho: RepositoriUM