Bicyclo 3.3.0 octane-3-ones

Nucleophilic addition of ester-derived enolate to the bicyclo[3.3.0]octan-2-one system of diacetone glucos-3-ulose usually occurs at the convex jS-face of the carbonyl (as for other nucleophiles), except for senecioate-derived enolate (from 3-methyl cro-tonate) for which a-attack in diethylether solvent is in contrast to the jS-face attack in THF the reason for this anomalous behaviour is not clear. 

Consider now bicyclooctanones. Of the nine possible species, there are three for which the desired thermochemistry is available in the literature bicyclo[2.2.2]octanone116117, and the cis- and trans-bicyclo[3.3.0]octan-2-ones, species 40a, 40b and 40c, respectively. We find the following 539 values 119, 137.2 5.3 and 140.1 ... 

Bicyclononanones are represented by cis- and traws-hexahydro-2-indanone, 41a and 41b, which like the above bicyclo[3.3.0]octan-2-ones are fused cyclopentanones. The values of 39 are 122.5 2.4 and 117.8 2.7 kJ mol-1. Another example is bicyclo[3.3.1]nonan-9-one126 (41c), for which 639 equals ca 112 kJmol-1. 

Bicyclic ketones are prepared by cycloadditions of methylenecyclopropanes with cyclic a,P-unsatu-rated carbonyl compounds. c J-Bicyclo[3.3.0]octan-2-ones (50), (51) and (52) are obtained in good yields by phosphine-nickel(0)-catalyzed cross coupling reactions of 2-cyclopentenone with methylenecyclopropanes in the presence of 0.1-1 equiv. of triethylborane as a Lewis acid (equations 18 and 19 and... 

C14H1sBrNfiO, 2,6-Dimethyl-3,4-dioxo-2,3,4,6,7,8-hexahydropyrid-azino[4,3-c]pyridazine-4-[p-bromophenylhydrazone], 46B, 250 Cl4H1fiBrNO, 3-(p-Bromobenzyl)-l-aza-bicyclo[3.3.0]octan-2-one, 45B, 269... 

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