Reductive Coupling of Allylic Esters with Carbonyl Compounds Mediated by the Mischmetall/[SmI2/Pd0cat.′]cat. System
作者:Sédami Médégan、Florence Hélion、Jean-Louis Namy
DOI:10.1002/ejoc.200500291
日期:2005.11
“two-stage catalysis” has been carried out using SmI2 and Pd(PPh3)4 in catalytic amounts together with mischmetall (an alloy of the light lanthanides) as a co-reductant. A catalytic scheme that takes into account previously reported reactions of SmI2/Pd0cat. and mischmetall/SmI2,cat. systems is proposed. It has also been shown that palladium complexes catalyse the addition of organolanthanide species
Nickel-catalyzed efficient umpolung allylation of ketones with allyliccarbonates in the presence of zinc powder is developed, which accommodates a variety of allylic and ketone substrates. Although chiral ligand is necessary for the transformation, no enantioselectivity was observed. Nickel-catalyzed efficient umpolung allylation of ketones with allyliccarbonates in the presence of zinc powder is developed
Synthesis of Tetrahydrofurans by Cyclization of Homoallylic Alcohols with Iodine/Iodine(III)
作者:Ramon S. Vasconcelos、Luiz F. Silva、Athanassios Giannis
DOI:10.1021/jo102413u
日期:2011.3.4
Tetrahydrofuran derivatives can be obtained by cyclofunctionalization of homoallylicalcohols bearing a terminal double bound by using [hydroxy(tosyloxy)iodo]benzene (HTIB, Koser’s reagent) in the presence of a catalytic amount of I2 (20 mol %) in MeOH under mild conditions. This transformation is an overall5-endo-trig cyclization, which occurs by two different pathways. The first is a 4-exo-trig
Organomanganese (II) reagents XX: Manganese mediated Barbier and Reformatsky like reactions an efficient route to homoallylic alcohols and β-acetoxyesters
作者:Gérard Cahiez、Pierre-Yves Chavant
DOI:10.1016/s0040-4039(00)70700-3
日期:1989.1
Allylic halides and α-bromoesters react with manganese metal in ethyl acetate; THF can also be used as solvent if a catalytic amount of zinc chloride is added to the reaction mixture. When the reaction is performed in the presence of various aldehydes or ketones, excellent yields of 1,2-addition products are obtained in preparative conditions.
Selectivity in Lewis acid-mediated fragmentations of peroxides and ozonides: application to the synthesis of alkenes, homoallyl ethers, and 1,2-dioxolanes †
作者:Patrick H. Dussault、Hyung-Jae Lee、Xuejun Liu
DOI:10.1039/b001391i
日期:——
Fragmentation of dialkyl peroxides and ozonides is strongly influenced by the choice of Lewis acid. TiCl4 promotes C–O ionization (SN1 reaction) of tertiary peroxides while SnCl4 and BF3·OEt2 promote O–O heterolysis (Hock reaction). The cationic intermediates are trapped with allyltrimethylsilane to afford allylated alkanes and homoallyl ethers. In the absence of a nucleophile, ozonides (1,2,4-trioxolanes) invariably undergo O–O heterolysis. However, the combination of allyltrimethylsilane and SnCl4 results in formation of 1,2-dioxolanes via trapping of intermediates derived from SN1 ionization.