P(NMe2)3-Mediated Umpolung Alkylation and Nonylidic Olefination of α-Keto Esters
A commercial phosphorus-based reagent (P(NMe2)3) mediates umpolung alkylation of methyl aroylformates with benzylic and allylic bromides, leading to either Barbier-type addition or ylide-free olefination products upon workup. The reaction sequence is initiated by a two-electron redox addition of the tricoordinate phosphorus reagent with an α-keto ester compound (Kukhtin-Ramirez addition). A mechanistic rationale is offered for the chemoselectivity upon which the success of this nonmetal mediated C-C bond forming strategy is based.
Wang, Sunewang Rixin,Radosevich, Alexander T.
p. 3810 - 3813
(2015/08/18)
Synthesis of dineophyltin dihydride and stereoselective hydrostannation of alkynes and (E)-trisubstituted alkenes
This paper reports the synthesis of dineophyltin dihydride (3) following two procedures. The four steps synthesis starting from benzyl chloride and Sn was shown to be more convenient than the two step direct alkylation of SnCl 4. The study of the free radical hydrostannation of mono- and disubstituted acetylenes with hydride 3 shows that they are stereoselective and that the stereoisomers obtained in higher proportion are stable and easily separated by column chromatography. Some preliminary studies on the chemical reactivity of the new divinylsubstituted dineophyltin compounds in Stille reactions are also informed. Radical hydrostannatation of (E)-trisubstituted ethylenes with 3 did not succeed probably due to steric factors. The preparation of dineophyltin bromohydride (27) is also reported. Radical addition of 27 to methyl (E)-2,3-disubstituted propenoates leads to mixtures of the corresponding erythro and threo adducts in diastereomeric excesses (d.e.) in the range of 74-90%.
Zú?iga, Adriana E.,Fidelibus, Pablo M.,Mandolesi, Sandra D.,Podestá, Julio C.
experimental part
p. 1547 - 1555
(2011/06/17)
Palladium-catalyzed cross coupling reaction of benzyl bromides with diazoesters for stereoselective synthesis of (E)-α,β-diarylacrylates
(Chemical Equation Presented) A Pd-catalyzed cross-coupling reaction of benzyl bromides with α-aryldiazoesters is described, and E-α,β-diarylacrylates were obtained in good yields and excellent E-to-Z selectivity (>20:1).
Yu, Wing-Yiu,Tsoi, Yuk-Tai,Zhou, Zhongyuan,Chan, Albert S. C.
supporting information; experimental part
p. 469 - 472
(2009/07/11)
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