排序方式: 共有6条查询结果,搜索用时 15 毫秒
1
1.
Frédéric Cadoret 《Tetrahedron letters》2007,48(31):5491-5495
Competition experiments were performed by adding pre-formed solutions of diisopropyloxy(η2-cyclopentene)titanium in diethyl ether to various mixtures of unsaturated compounds at low temperature, establishing the following reactivity scale: aldehyde > nitrile > ketone > terminal alkyne > internal alkyne > terminal alkene > ester, carbonate. 相似文献
2.
Andrei V. Bekish 《Tetrahedron letters》2005,46(41):6975-6978
Ethoxycarbonyl groups in O-THP protected racemic diethyl malate 1 were differentiated by their reductive cyclopropanation with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide and subsequent site-selective C1-C2, C2-C3 or both C1-C2 and C1-C3 ring cleavage of the cyclopropyl groups of the resulting bis-cyclopropanol 2. 相似文献
3.
A range of amides fitted with (E) or (Z) disubstituted alkene groups were prepared and evaluated in intramolecular Kulinkovich-de Meijere reactions. The corresponding aminocyclopropanes were obtained with high diastereoselectivity. Good yields could be achieved with substrates bearing suitable substitutions at the olefin moieties. 相似文献
4.
Andrey V. Bekish 《Tetrahedron letters》2004,45(27):5253-5255
A convenient new approach to the synthesis of the acetate and the propionate of (2S,3R,7R/S)-3,7-dimethyltridecan-2-ol, sex attractants of Diprion pini L., using the cyclopropanation of the ethoxycarbonyl group in O-THP protected ethyl (S)-lactate with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide followed by C-2-C-3 cyclopropane ring opening as the key steps has been performed. 相似文献
5.
Dzmitry G. Kananovich 《Tetrahedron》2008,64(7):1536-1547
Datа on the stereochemistry of the intramolecular cyclization of β-metaloketones into 1,2-disubstituted cyclopropanols are in agreement with the cyclopropanation of carboxylic esters with alkoxytitanacyclopropane reagents proceeding via the β-titanoketone intermediates with the metal atom bound to a secondary carbon. Hypothesis for the origin of cis-diastereoselectivity of the cyclization of the β-titanoketones is suggested. It explains the tendency for the preferable formation of cis-1,2-disubstituted cyclopropanols by relief of repulsion strain between the ligands at the octahedral titanium atom. 相似文献
6.
Dzmitry G. Kananovich 《Tetrahedron letters》2007,48(48):8424-8429
Methanesulfonates of readily available cis-1,2-disubstituted cyclopropanols on reaction with magnesium bromide in diethyl ether undergo cyclopropyl-allyl rearrangement to afford allyl bromides, with an (E)-trisubstituted double bond, as main products. The amount of the corresponding (Z)-isomers did not exceed 5% when the reaction was performed at 0 °C, and the major concomitant products were the regioisomeric secondary bromides. The latter are sufficiently less reactive towards sulfur, phosphorus and hydrogen nucleophiles than the dominant (E)-disubstituted allyl bromides and these reactions are suitable for the stereoselective preparation of trisubstituted olefins. 相似文献
1