Myers-Saito and Schmittel Routes to Indeno-Fused Structures

3 CYCLOAROMATIZATION BY Cl-C C -C AND C -C (MYERS-SAITO AND SCHMITTEL) ROUTES TO INDENO-FUSED STRUCTURES 

Quantum-chemical BLYP/6-31G calculation of the relative activation energies for conversion of the enediyne to intermediate 3.531 [ a(C -C ) = 38.7 kcal/mol] and to intermediate 3.534 [ a(C -C ) = 43.2 kcal/mol) indicated a preference for the C -C pathway. This was attributed to the presence of sterically bulky substituents in the acetylenic branches that determine the transition state energy of the Bergman cycloaromatization, as well as for the change in the pathway 

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