prepared and used successfully as an acetylene equivalent in the synthesis of substituted cyclopentenones. TMNBD is easily accessible on a multigram scale and displays excellent reactivity toward the intermolecular Pauson–Khand reaction. Conjugate additions on the resulting tricyclic compounds proceed with exquisite diastereoselectivity. The retro-Diels–Alder reaction of these TMNBD derivatives occurs under
Hydroxylic additives enhance yield and scalability of silicon-directed Nazarov reaction
作者:Shaon Joy、Waka Nakanishi、F.G. West
DOI:10.1016/j.tetlet.2013.07.139
日期:2013.10
As a result of difficulties in scaling up silicon-directedNazarovcyclization for use in the synthesis of taxane natural products, the effect of additives was examined. Hydroxylic additives were found to convey a consistent beneficial effect on the rate, overall yield, and scalability of these reactions. Optimal conditions (1.5 equiv methanol or water with substoichiometric FeCl3), were successfully
Silicon-DirectedNazarov Reactions II. Preparation and Cyclization of ?-Silyl-substituted Divinyl Ketones
作者:Todd K. Jones、Scott E. Denmark
DOI:10.1002/hlca.19830660802
日期:1983.12.14
Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones. Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring. The observed effects of substituents
A Pauson−Khand-Type Reaction between Alkynes and Olefinic Aldehydes Catalyzed by Rhodium/Cobalt Heterobimetallic Nanoparticles: An Olefinic Aldehyde as an Olefin and CO Source
作者:Kang Hyun Park、Il Gu Jung、Young Keun Chung
DOI:10.1021/ol049765s
日期:2004.4.1
Co/Rh (Co:Rh = 2:2) heterobimetallic nanoparticles derived from Co(2)Rh(2)(CO)(12) react with alkynes and alpha,beta-unsaturated aldehydes such as acrolein, crotonaldehyde, and cinnamic aldehyde and release products resulting from [2 + 2 + 1]cycloaddition of alkyne, carbon monoxide, and alkene. alpha,beta-Unsaturated aldehydes act as a CO and alkene source. These reactions produce 2-substituted cyclopentenones
Asymmetric [2+2+1] cyclopentannulation of olefins. Ring expansion of 2-N-methyl-N-tosyl-cyclobutanone
作者:Florence Mahuteau-Betzer、Léon Ghosez
DOI:10.1016/s0040-4020(02)00694-4
日期:2002.8
factors which have been analyzed. Treatment of these oxiranes with a stoichiometric amount of lithium iodide in refluxing tetrahydrofuran gave excellent yields of monocyclic or fused cyclopentenones 4 resulting from a β-elimination of N-methyl-N-tosylamide from a primarily formed cyclopentanone. The ring-expansion was totally selective but for oxiranes attached to a bicyclo[4.2.0]octanone system. In all