Electronic Factors in Photo-BC

The substituted naphthalene structures for the products were assigned on the basis of mass-spectral analysis and their conversion to naphthalene upon hydrogenolysis. The yields for the cyclic products were low, most likely due to the lack of suitable H-donor in these experiments. 

SCHEME 30.1 First report of photochemical Bergman cyclization. 

SCHEME 30.2 Photochemical Bergman cyclization of aromatic enediynes. 

Generally, reactions can be accelerated via transition state stabilization or reactant destabilization, which for enediynes can be investigated by varying the electronic nature of substituents at either the ene or aUcynyl end or by inducing ring strain. 

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