Stereoselective Activation of Small Molecules by a Stable Chiral Silene |
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Authors: | Xiaofei Sun Dr. Alexander Hinz Hannes Kucher Dr. Michael T. Gamer Prof. Dr. Peter W. Roesky |
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Affiliation: | Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstraße 15, 76131 Karlsruhe, Germany |
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Abstract: | The reaction of the dilithium salt of the enantiopure (S)-BINOL (1,1’-bi-2-naphthol) with two equivalents of the amidinate-stabilized chlorosilylene [LPhSiCl] (LPh=PhC(NtBu)2) led to the formation of the first example of a chiral cyclic silene species comprising an (S)-BINOL ligand. The reactivity of the Si=C bond was investigated by reaction with elemental sulfur, CO2 and HCl. The reaction with S8 led to a Si=C bond cleavage and concomitantly to a ring-opened product with imine and silanethione functional groups. The reaction with CO2 resulted in the cleavage of the CO2 molecule into a carbonyl group and an isolated O atom, while a new stereocenter is formed in a highly selective manner. According to DFT calculations, the [2+2] cycloaddition product is the key intermediate. Further reactivity studies of the chiral cyclic silene with HCl resulted in a stereoselective addition to the Si=C bond, while the fully selective formation of two stereocenters was achieved. The quantitative stereoselective addition of CO2 and HCl to a Si=C bond is unprecedented. |
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Keywords: | group 14 silene silicon small molecule activation stereoselectivity |
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