Stereoselective Synthesis of Medium-sized Cyclic Compounds through the Intramolecular Michael-type Reaction Utilizing Alkyne-Hexacarbonyldicobalt Complex Formation

  title={Stereoselective Synthesis of Medium-sized Cyclic Compounds through the Intramolecular Michael-type Reaction Utilizing Alkyne-Hexacarbonyldicobalt Complex Formation},
  author={Kennichi Inaba and Jun Takaya and Nobuharu Iwasawa},
  journal={Chemistry Letters},
Alkyne–hexacarbonyldicobalt complexes having silyl enol ether and electron-deficient alkene moieties on opposite ends were treated with MeAlCl2 in the presence of 2,6-di-t-butylpyridine in CH2Cl2 t... 
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Experimental studies suggest that the dehydrotropylium-Co(2)(CO)(6) ion is weakly aromatic, and its homodesmotic-reaction-based stabilisation energy and its NICS(1) value suggest that this ion was generated by the action of HBF or BF(3)⋅OEt(2).


A general approach to medium ring alkynes by using metathesis of cobalt hexacarbonyl containing dienes.
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Stereoselective synthesis of eight-membered cyclic ethers by tandem Nicholas reaction/ring-closing metathesis: a short synthesis of (+)-cis-Lauthisan.
Key steps in such synthesis were the ether linkage formation by intermolecular Nicholas reaction, RCM of the suitable acyclic dienyl ether and montmorillonite K-10 induced isomerization of the complexed cycloalkyne.
Stereoselective synthesis of cycloheptanone derivatives via an intermolecular [5 + 2] cycloaddition reaction.
A cycloaddition reaction of a new five-carbon unit was developed on the basis of a dicobalt hexacarbonyl propargyl cation species that can be easily converted into various kinds of cycloheptanone derivatives.
Complexation-Initiated Intramolecular Diels-Alder Reaction.
A complexation-initiated intramolecular Diels-Alder reaction was demonstrated for the first time and seven-membered ring formation was apparently favorable in this system.
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Reductive decomplexation of acetylenebiscobalthexacarbonyl is best achieved with tri-n-butyltin hydride. Instead of this toxic reagent, sodium hypophosphite monohydrate has proved to be a safe,
6-Bromomethyl-4H-1,3-dioxin: a versatile bromomethyl vinyl ketone equivalent for heterocycle and carbocycle construction.
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