Abstract
Radical‐Type Cyclisation of Dienes, 111. – Radical‐Type Cyclisation of (R)‐( – )‐Carvone – On the Influence of Charge‐ Transfer Interactions on the Optical RotationUnder the conditions of radical cyclisation, a 1:1 diastereomeric mixture of (1R,2S,5R,R)‐(+)‐ (2a) and (1R.2S,5R,6S)‐(+)‐6‐methoxy‐2,6‐dimethylbicyclo[3.2.1]octan‐3‐ones (2b) is obtained from (R)‐(‐)‐carvone in 70% yield. the configuration fo 2a and 2b were confirmed by X‐ray structure analyses of their hydrazones 2d and 2e. The regio‐ and stereoselectivity of the radical cyclisation of 1 to 2a and 2b are discussed. The high value of the specific rotation [‐555] of 2d is traced back to charge‐transfer interactions between the endo‐standing methoxy group at C‐6 as electron donor and the dinitrophenyl‐hydrazone group as electron acceptor.
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