4-Isopropenyl-2-cyclohexanone

The syntheses of nootkatone (356) and a-vetivone (357) have been described in full, van der Gen et have used a different approach to generate the requisite 2-methyl-4-isopropylidene(isopropenyl)cyclohexanone for further elaboration by Robinson annotation. They have found that ring-opening of (-i-)-cis-3-methylnopinone (358), derived from ( —)- -pinene, with sulphuric and... 

When certain cyclodipeptides are used as catalysts for the enantioselective formation of cyanohydrins, an autocatalytic improvement of selectivity is observed in the presence of chiral hydrocyanation products [80]. A commercial process for the manufacture of a pyrethroid insecticide involving asymmetric addition of HCN to an aromatic aldehyde in the presence of a cyclic dipeptide has been described [80]. Besides HCN itself, acetone cyanohydrin is also used (usually in the literature referred to as the Nazarov method), which can be activated cata-lytically by certain lanthanide complexes [81]. Acetylcyanation of aldehydes is described with samarium-based catalysts in the presence of isopropenyl acetate cyclohexanone oxime acetate is hydrocyanated with acetone cyanohydrin as the HCN source in the presence of these catalytic systems [82]. 

Rearrangement Reaction. The copolymers were dissolved in freshly distilled DMF or cyclohexanone (ca. 10% solids) and heated under reflux while a dry nitrogen stream was passed through the solution. After 1.5 hrs of reaction, only a trace amount of amine was detectable in the distillate. The solution was allowed to cool, and the isopropenyl isocyanate copolymers were then isolated by pouring the thermolyzed polymer solution into a large excess of non-solvent. The polymers were filtered, washed, redissolved in chloroform, and then analyzed. 

In contrast, dimethylsulfoxonium methylide [(CH3)2S" (0)CH2 ] reacts with a,P-unsaturated ketones such as R-(-)-5-isopropenyl-2-methylcyclohex-2-en-l-one [R-(-)-carvone] to produce the cyclopropane product of conjugate addition (Scheme 9.57), 4-isopropenyl-l-methylbicyclo[4.1.0]heptan-2-one, and addition to 4-t-butyl-cyclohexanone produces the product resulting from equatorial attack (exclusively) (Scheme 9.58). 

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