Iododesilylation of TIPS-, TBDPS-, and TBS-Substituted Alkenes in Connection with the Synthesis of Amphidinolides B/D
摘要:
The C-Si bonds of triisopropylsilyl-substituted alkenes, 1,3-dienes, and related multifunctional substrates, as well as analogous C-TBDPS and C-TBS bonds, are readily and chemoselectively cleaved with NIS (or other sources of I(+), such as N-iodosaccharin, 1,3-diodohydantoin, and Ipy(2)BF(4)). The desired iodoalkenes are obtained stereospecifically without byproducts, provided that the reactions are carried out in CF(3)CHOHCF(3) and, in general, with 30 mol % of Ag(2)CO(3) (or AgOAc/2,6-Iutidine) as an additive. Fragment C10-C18 of cytotoxic amphidinolides B1-B3 and D has been synthesized using this improved procedure.
Five-membered metallacycloallene compounds that are 2,5-disubstituted 1-zirconacyclopenta-2,3-dienes were prepared from (E)-1,4-bis(trialkylsilyl)but-1-en-3-ynes in good yields. The structures of these compounds were determined by X-ray diffraction study. Contrary to our previous study on 2,4-disubstituted 1-zirconacyclopenta-2,3-dienes, which gave alkynyl alcohols by the reaction with ketones after
Regio- and Stereoselective Homodimerization of Monosubstituted Acetylenes in the Presence of the Second Generation Grubbs Catalyst
作者:Beata Powała、Cezary Pietraszuk
DOI:10.1007/s10562-013-1134-z
日期:2014.3
Silyl- and phenylacetylenes undergo efficient homodimerization in the presence of a second generation Grubbs catalyst. The reaction permits fully regio- and stereoselective synthesis of disubstituted 1,3-enynes. The other commonly used ruthenium-based olefin metathesis catalysts remain inactive in the reaction.