71060-35-0Relevant academic research and scientific papers
Studies on asymmetric conversion of arenes to functionalized cyclohexenones via chiral auxiliary-promoted nucleophilic additions to arene-chromium complexes
Pearson, Anthony J.,Gontcharov, Alexander V.,Woodgate, Paul D.
, p. 3087 - 3088 (1996)
Reactions of alkoxyarene-chromium tricarbonyl complexes, having chiral alkoxy groups, with isobutyronitrile anion, followed by standard work-up produces substituted alkoxycyclohexadienes with diastereomeric excesses of up to 76%. Conversion to cyclohexeno
Asymmetric Conversion of Arenechromium Complexes to Functionalized Cyclohexenones: Progress toward Defining an Optimum Chiral Auxiliary
Pearson, Anthony J.,Gontcharov, Alexander V.
, p. 152 - 162 (2007/10/03)
An investigation into the asymmetric synthesis of 5-substituted cyclohexenones via nucleophile addition to (alkoxyarene)chromium tricarbonyl complexes is described. Diastereoselectivity during the nucleophile addition step was achieved using alkoxy substituents derived from terpenoid substrates as chiral auxiliaries. Selectivities as high as 24:1 were obtained when 2-phenylisoborneol was used as the chiral auxiliary and as high as 17:1 using 3,3-(ethylenedioxy)isoborneol. The absolute stereochemistry of the major products was assigned by Mosher's method, after their conversion to the corresponding cyclohexenol. A study of the temperature dependence of the nucleophile addition to alkoxytoluene complexes revealed a thermodynamic preference for addition ortho to the ether substituent.
ADDITION OF CARBON NUCLEOPHILES TO ARENE-CHROMIUM COMPLEXES
Semmelhack, M.F.,Clark, G.R.,Garcia, J.L.,Harrison, J.J.,Thebtaranonth, Y.,et. al
, p. 3957 - 3965 (2007/10/02)
The electrophilic reactivity of arenes coordinated to the chromium tricarbonyl unit has been developed into several distinct methods for coupling carbon nucleophiles with aromatic rings.Addition of the nucleophile produces stable η-cyclohexadienyl chromium complexes which can be oxidized to induce loss of the endo hydrogen and the metal, overall nucleophilic substitution for hydrogen.Alternatively, the intermediate can be protonated and the resulting cyclohexa-1,3-diene can be detached from the chromium, effecting nucleophilic addition with reduction of one double bond.If a halogen (F, Cl) is present as a ring substituent, and if the nucleophile can migrate about the arene ligand, then loss of halide can occur parallel with classical nucleophilic aromatic substitution for halogen in electron-deficient haloarenes.With substituted arenes, the regioselectivity of addition becomes important and is often very high.Particularly useful are strong resonance donor substituents (RO-, R2N-, F-) where selectivity for meta attack is high.Indole provides an excellent example of selective activation, as the six-membered ring complexes selectively and is then susceptible to nucleophilic substitution, predominantly at the 4 and 7 positions.Substitution for halogen is a somewhat limited process and depends upon the nature of the nucleophile.Very reactive nucleophiles add to unsubstituted positions and are often slow to isomerize to the ipso position from which loss of halide can occur.
