Structure and stereochemistry of cyclodimers obtained by acid treatment of trans-stilbenes and of N-1,2-diarylethylamides

The reaction of trans-stilbenes and N-1,2-diarylethylamides with ethyl polyphosphate affords indanes and tetralins with three stereogenic centres. The structural and configurational assignment of the cyclodimers is based mainly on the NMR and MS data. A possible transition state for the reaction is discussed.