Herein, we report a comprehensive theoretical investigation on highly stereospecific monochlorination of adamantylideneadamantane (Ad=Ad) with Cl2 and NCS in CCl4. For the reaction without radical initiators, ion-pair mechanism well rationalizes the unique stereospecificity. It involves three consecutive steps: formation of ion-pair species (Ad=Ad-Cl+/Cl- and Ad=Ad-Cl+/NS-), stereospecific proton abstraction from 4-axial (4-a) position and kinetically preferred intramolecular 4-equatorial (4-e) cyclopropylcarbinyl-homoallylic rearrangement.As to the reaction with the presence of radical initiators, the free radical mechanism fails to explain the experimental results, but the radical cation mechanism works well. In this channel, Ad=Ad+� is formed via one-electron oxidization with the assistance of oxidants like Cl�, NS� and Ad=Ad-Cl+. Then the stereospecific 4-e-Ad=Ad+ formed by hydrogen loss from 4-e position of Ad=Ad+� interacts with chloride anion and gives the final product.

Mechanism on remarkably stereospecific monochlorination of adamantylideneadamantane

247th National Meeting (2014)

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