Catalytic Enantioselective Three-Component Hetero-[4+2] Cycloaddition/Allylboration Approach to α-Hydroxyalkyl Pyrans: Scope, Limitations, and Mechanistic Proposal
作者:Xuri Gao、Dennis G. Hall、Michael Deligny、Annaick Favre、François Carreaux、Bertrand Carboni
DOI:10.1002/chem.200501197
日期:2006.4.3
hetero-[4+2] cycloaddition/allylboration reaction between 3-boronoacrolein, enol ethers, and aldehydes to afford alpha-hydroxyalkyl dihydropyrans. The key substrate, 3-boronoacrolein pinacolate (2) was found to be an exceptionally reactive heterodiene in the hetero-[4+2] cycloaddition catalyzed by Jacobsen's chiral Cr(III) catalyst 1. The scope and limitations of this process were thoroughly examined
Microwave-Assisted Convenient Synthesis of<i>α</i>,<i>β</i>-Unsaturated Esters and Ketones<i>via</i>Aldol-Adduct Elimination
作者:Pathi Suman、Rayala Nageswara Rao、Bhimapaka China Raju
DOI:10.1002/hlca.201200526
日期:2013.8
Various fluorinated 3‐oxo ester/1,3‐diketones were reacted with carbonyl compounds, in presence of piperidine and under microwave irradiation, to afford (E)‐α,β‐unsaturated esters and ketones in good yields. The systematic study reveals that the reaction proceeded through the formation of aldol adduct. The method provides a new and simple way for C,C bond formations.
The diastereoselective synthesis of β-substituted α-hydroxyphosphinates was achieved by hydrophosphinylation of α-oxy aldehydes and α-amino aldehydes with ethyl allylphosphinate catalyzed by lithium phenoxide.
A variety of terminal alkenes are produced in excellent yields by the rhodium(I)-catalyzed methylenation of aldehydes using TMSCHN2 and PPh3 [Eq. (1)]. These mild reaction conditions allowed the conversion of enolizable substrates and the chemoselective methylenation of aldehydes over ketones. TMS=trimethylsilyl.
Stereoselective 1,4-addition of Grignard reagents to chiral γ-alkoxy-α,β-unsaturated ketones
作者:Jerzy Raczko
DOI:10.1016/s0957-4166(97)00520-x
日期:1997.11
Copper-catalyzed conjugate addition reactions of Grignardreagents to γ-alkoxy-α,β-unsaturated ketones, derived from mandelic acid, have been studied. Diastereoselectivity is strongly dependent on the nature of the γ-alkoxy protection group. Bulky silyl protection gives poor stereoselectivities, whereas the ketone bearing benzyloxymethylene (BOM) protection reacts with excellent yields and stereoselectivities