Lewis acid catalyzed stereoselective hydrosilylation of ketones under the control of σ–π chelation

Autor:	Takeshi Ohishi, Yoshinori Yamamoto, Naoki Asao, Kenichiro Sato
Rok vydání:	2002
Předmět:	chemistry.chemical_classification Stereochemistry Hydrosilylation Aryl Organic Chemistry Alkyne General Medicine Medicinal chemistry Biochemistry chemistry.chemical_compound chemistry Drug Discovery Silylium ion Stereoselectivity Chelation Lewis acids and bases Lone pair
Zdroj:	Tetrahedron. 58:8195-8203
ISSN:	0040-4020
DOI:	10.1016/s0040-4020(02)00968-7
Popis:	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.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::12974607148363dee428b15850dcfeb2 https://doi.org/10.1016/s0040-4020(02)00968-7 Zobrazit plný text záznamu Full Text from ScienceDirect