Reductive dimerization of telluro- and selenoxanthone

By treating an equimolar mixture of telluroxanthone and selenoxanthone with Zn powder in boiling HO Ac and concentrated HCl (100 1.25) for 1 h, a reductive dimerization takes place giving the dimerized prodncts in the ratio 21 35 in addition to telluroxanthene and selenoxanthene.  

The observed distribution of the products, compared to the statistical distribution 25 25 50, clearly indicates that the Te/Te bridged B is preferred over the Se/Te bridged C, and Se/Se bridged A, while C is preferred over A. 

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