Spiro decanones

Organobis(cupratesY, spiroannelation.16 1,4-Dilithiobutane, prepared from 1,4-dichlorobutane and lithium in ether at 0°, on reaction with copper thiophenoxide (2 equiv.) forms a biscuprate, formulated as 1 for convenience. This dimetallic reagent adds to 3-halo-5,5-dimethyl-2-cyclohexenones (2) to form the spiro-[4.5]decanone 3 in yields as high as 96%. Cuprates prepared from other Cu(I) sources are less efficient, as is the cuprate prepared from di-Grignard reagents... 

Intramolecular cyclization of allylsilanes." An intramolecular version of the Sak-urai reaction (7, 371 11, 529-530) provides a route to functionalized spiro(4,5]decanones. For cyclization of 1 to 2, ethylaluminum dichloride is the preferred Lewis acid activator. The diastereoselectivity depends on the temperature and the solvent. 

This reaction was reinvestigated with cw-l,7-dimethyltricyclo[4.4.0.0 ]decan-3-one (30) as a model compound. The reduction with lithium to the spiro[4.5]decanone product occurred predominantly with inversion of configuration at the jS-carbon atom. However, the ratio of inversion to retention depends on the reaction temperature and the amount of alcohol added. Both higher temperature and more alcohol increased the proportion of the retention product. 

The influence of alkyl substituents on the direction of cleavage in a series of 1-methyl-tricyclo[4.4.0.0 ]decan-3-ones 39 has been studied. In the absence of an additional substituent, the formation of the brominated spiro[4.5]decanone compound 41 was slightly favored. 

In a different approach to the spiro[4,5]decane ring system, Naegeli " has synthesized decanones of the type (228) by way of cationic cyclizations of appropriate a,/8-unsaturated ketones, e.g. (227). 

Further investigations of the approach to spiro[4,5]decanones based on reductive cleavages of the cyclopropane rings in tricyclo[4,4,0,0, ]decanones have been forthcoming/ and the potential for oxycyclopropane derivatives in synthesis is very well demonstrated in a synthesis of j8-vetivone (230) from the /3-oxycyclopropyl ketone (229)/ ... 

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