Formation of Quaternary Stereogenic Centers by NHC-Cu-Catalyzed Asymmetric Conjugate Addition Reactions with Grignard Reagents on Polyconjugated Cyclic Enones
The copper‐catalyzedconjugateaddition of various Grignard reagents to polyconjugated enones (dienone and enynone derivatives) is reported. The catalyst system, composed of copper triflate and an NHC ligand, led to the unusual selective formation of the 1,4‐addition products. This reaction allows for the creation of all‐carbon chiral quaternary centers with enantiomeric excesses up to 99 %. The remaining
Carbonyl transposition on organoselenium compounds
作者:João V. Comasseto、Wai L. Lo、Nicola Petragnani
DOI:10.1016/s0040-4020(97)00454-7
日期:1997.6
Carbonyl conjugated vinylic selenides undergo 1,3 and 1,5-carbonyl transposition sequences through organometallic reagents addition reactions followed by acid hydrolysis.
羰基共轭乙烯基硒化物通过有机金属试剂加成反应进行1,3和1,5-羰基转座序列,然后进行酸水解。
Chemoselective Additions of Chloromethyllithium Carbenoid to Cyclic Enones: A Direct Access to Chloromethyl Allylic Alcohols
作者:Vittorio Pace、Laura Castoldi、Wolfgang Holzer
DOI:10.1002/adsc.201301042
日期:2014.5.26
Chloromethyllithium carbenoid has been chemoselectively added to cyclicenones (5‐, 6‐ and 7‐membered systems, including two natural products) to provide chloromethyl allylic alcohols. Under the optimized reaction conditions neither concomitant (n+1) homologation nor conjugateaddition or Simmons–Smith‐like cyclopropanation takes place. The presence of LiBr is estimated to play a dual role, namely
β,γ‐Unsaturatedaldehydes with all‐carbon quaternary or tertiary α‐centers were rapidly assembled from ketones through a unique synthetic operation consisting of 1) C1 homologation, 2) Lewis acid mediated epoxide–aldehyde isomerization, and 3) electrophilic trapping. The synthetic equivalence of a vinyl oxirane and a β,γ‐unsaturatedaldehyde is the key concept of this previously undisclosed tactic
Heterogeneous versus Homogeneous Copper(II) Catalysis in Enantioselective Conjugate-Addition Reactions of Boron in Water
作者:Taku Kitanosono、Pengyu Xu、Shū Kobayashi
DOI:10.1002/asia.201300997
日期:2014.1
reported for the conjugateaddition of boron. Heterogeneous cat. 1 also gave high yields and enantioselectivities with some substrates and also gave the highest TOF (43 200 h−1) for an asymmetric conjugate‐additionreaction of boron. In addition, the catalyst systems were also applicable to the conjugateaddition of boron to α,β,γ,δ‐unsaturated carbonyl compounds, although such reactions have previously