Cyclopropanes Substituted with Phenyl Aryl Groups

2 Cyclopropanes Substituted with Phenyl(Aryl) Groups 

The reduction of 1-methyl-2,2-diphenylcyclopropane 42 and one of its enantiomers, (+)-(R) 2, with Na/NHj to give 1,1-diphenylbutane 43 and l,l-diphenyl-2-methyl-propane 44 in a — 5.5 1 ratio over a wide concentration range has been studied by Walborsky and Pierce M ). 

The role of the phenyl groups (and similarly of the carbonyl groups in 33, 37,39, cis-40 and trans-41) is to accept an electron to give the short-lived radical anion 45. ESR experiments have so far failed to demonstrate the existence of45 48), and of the 

The predominant formation of 43 from 42 via 1,2-bond cleavage of 45 to give 46 is expected on the basis that the trimethylene radical anion 46 would be predicted to be more stable than the trimethylene radical anion 47. This argument is based on the reasonable assumption that in 46 there is more negative charge on the carbon atom bearing the two phenyl groups otherwise the isomer 47 should be more stable. 

It seemed unlikely that, instead of the radical anions 46 and 47, the corresponding l,3- dianions had been formed directly from their common cyclopropane dianion precursor. This, however, has not been rigorously excluded by means of these experiments. 

---