Adamantane derivatives, nucleophilic substitution

Photostimulated, S r k 1 reactions of carbanion nucleophiles in DMSO have been used to advantage in C—C bond formation (Scheme 1).25-27 Thus, good yields of substitution products have been obtained from neopentyl iodide on reaction with enolates of acetophenone and anthrone, but not with the conjugate base of acetone or nitromethane (unless used in conjunction, whereby the former acts as an entrainment agent).25 1,3-Diiodoadamantane forms an intermediate 1-iodo mono substitution product on reaction with potassium enolates of acetophenone and pinacolone and with the anion of nitromethane subsequent fragmentation of the intermediate gives derivatives of 7-methylidenebicyclo[3.3.1]nonene. Reactions of 1,3-dibromo- and 1-bromo-3-chloro-adamantane are less effective.26... 

Relative reactivity studies of homolytic substitution of monosubstituted benzene derivatives reveal that the 1-adamantyl radical has more pronounced nucleophilic properties than have other, more strained, bridgehead radicals. With benzo-nitrile 21.1) almost exclusive para-substitution is observed, whereas with anisole 0.65) the three possible sites are attacked almost equally. Kinetic studies on the reaction of adamantanethione with adamantane-2-thiol indicate that the rate-controlling chain-propagation step is hydrogen abstraction from the thiol (AdHSH) by the carbon-centred radical AdHSSAd-, and that the main mode of termination involves the diffusion-controlled bimolecular self-reaction of these radicals. ... 

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