Abstract
Hydrosilylation of 2-methyl-1-phenyl-pentan-1-one with Et3SiH in the presence of catalytic amounts of B(C6F5)3 gave the anti-product with slight predominance over syn-product (syn/anti=1:1.5). In contrast, the syn-product was obtained stereoselectively in the reaction of 2-methyl-1-phenyl-pent-4-yn-1-one bearing an ethynyl group at the β-position (syn/anti=7:1). The syn-selectivities were also observed in the B(C6F5)3-catalyzed reactions of other related ketones, such as α-methyl-β-alkynyl aryl ketones and α-methyl-β-alkynyl alkyl ketones. The moderate anti-selectivity observed in the former case can be explained by the ordinary Felkin-Anh model. On the other hand, the unusual syn-selectivity in the latter cases can be accounted for by the σ-π chelation by R3Si+, in which both the lone pair (σ) of the carbonyl group and the π-electrons of the alkyne coordinate to the silylium ion. The σ-π chelation control was also effective for the 1,3-asymmetric induction.
Original language | English |
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Pages (from-to) | 8195-8203 |
Number of pages | 9 |
Journal | Tetrahedron |
Volume | 58 |
Issue number | 41 |
DOIs | |
Publication status | Published - 2002 Oct 7 |
Keywords
- Alkynes
- Chelation
- Ketones
- Stereocontrol
ASJC Scopus subject areas
- Biochemistry
- Drug Discovery
- Organic Chemistry