ORGN 159

Our recent research on the intervention of reaction dynamics on dihalocarbene additions to cyclopropenes has prompted us to investigate the mechanisms of dihalocarbene (CX₂; X = Br, Cl) and phenylhalocarbene (PhCX, X = Br, Cl) additions to other strained C-C p- and s-bonds.  Here, we look at additions of the above halocarbenes to cyclooctyne (1), cycloheptyne, and trans-1-methylbicyclo[6.1.0]nonane (3).  In our hands, CX₂ and PhCX additions to cyclooctyne produce halogenated products, even after aqueous workup.  These products appear to be formed as a result of traditional carbene cycloaddition to the alkyne bond (2), with likely post-addition rearrangement.  These results are in agreement with our completed computational investigations which suggest that cyclooctyne is not strained enough for CCl₂ and PhCCl additions to be subject to dynamic effects.  In the area of CX₂ and PhCX additions to strained C-C s-bonds, these carbenes add to parent trans-bicyclo[6.1.0]nonane in very low yields.  Installation of a bridgehead methyl group is expected to increase the nucleophilicity of the substrate's strained trans-fused three-membered ring, thereby promoting addition of CX₂ and PhCX, likely through concurrent central and side bond cleavage to 4.