A highly stereoselective direct aldol condensation of ketones to aromatic aldehydes was realized; the trichlorosilyl enolether generated in situ in the presence of tetrachlorosilane is activated by catalytic amounts of an enantiomerically pure biheteroaromatic phosphine oxide to react with aldehydes, coordinated as well as activated by the chiral cationic hypervalent silicon species. This Lewis acid-mediated Lewis base-catalyzed transformation allowed, starting from two carbonyl compounds, to directly synthesize β-hydroxy ketones generally with high anti stereoselectivity and up to 93% ee for the anti isomer.
Biheteroaromatic diphosphine oxides-catalyzed stereoselective direct aldol reactions / S. Rossi, M. Benaglia, A. Genoni, T. Benincori, G. Celentano. - In: TETRAHEDRON. - ISSN 0040-4020. - 67:1(2011), pp. 158-166. [10.1016/j.tet.2010.11.009]
Biheteroaromatic diphosphine oxides-catalyzed stereoselective direct aldol reactions
S. RossiPrimo
;M. BenagliaSecondo
;A. Genoni;G. CelentanoUltimo
2011
Abstract
A highly stereoselective direct aldol condensation of ketones to aromatic aldehydes was realized; the trichlorosilyl enolether generated in situ in the presence of tetrachlorosilane is activated by catalytic amounts of an enantiomerically pure biheteroaromatic phosphine oxide to react with aldehydes, coordinated as well as activated by the chiral cationic hypervalent silicon species. This Lewis acid-mediated Lewis base-catalyzed transformation allowed, starting from two carbonyl compounds, to directly synthesize β-hydroxy ketones generally with high anti stereoselectivity and up to 93% ee for the anti isomer.
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