7237(27) This type of mechanism was also suggested by Romans, et al.,2 for the oxidation of tetramethylhydrazine with iodine.

Cyclic 1,4-semidiones (radical anions of A2-1,4-diones) have been prepared in the cyclopentane, cyclohexane, and cycloheptane systems and detected by esr spectroscopy. Conformational preference and mobility have been detected in the 1,4-semidiones derived from A8x9-1,5-diketohydrindan and 1,6-diketodecalin systems. Examples of valence isomerization are reported in the preparation of 1,4-semidiones from eucarvone, A3-2-acetoxycaren-5-one, 2.3-benzocyclohept-4-enone, and pentacyclo[6.2.2.027.04.'0.0j.9]dodecane-3,6-dione.

27) A. de Meljere has discovered radical chlorination with tert-butyl hypochlorite to be a useful route to Introduction of chlorine at the C-1 bridgehead position of bicyclo[2.2.2]octane and blcyclo[3.3.2]decane systems to which at least one cyclopropane unit has been fused, such as trlshomobarrelene, trlshomobullvalene, and tricyclo[3.2.2.0s•4] nonane. A. de Meljere, O. Schallner, and C. Weitemeyer, Angew. Chem., Int. Ed. Engl., 11, 56 (1972), and a private communication. (28) Photochlorinatlon of norbornane with tert-butyl hypochlorite in CCI4 gives 1-chloro, 7-chloro, and a mixture of exo-and erxfo-2-chloronorbornane In a ratio of 1.6:2.2:96.2, T. D. Zlebarth, unpublished observation.(29) For a discussion and suggestive evidence supporting a colinear transition state for hydrogen atom transfer reactions, see

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