The cobalt-catalysed benzannulation of 2-pyridine-substituted enynes gave 2,3-bis(2-pyridyl)styrenes in moderate yields. The reaction with dibromomethane as well as diiodomethane generated the corresponding planar-chiral bispyridinium salts in good yields. On the other hand, the transformations with reagents of the type RCHBr2 to afford diastereomeric products led to the desired conversion. However, these products could not be obtained in pure form.
Key words
benzannulation - cobalt - enynes - pyridines - styrenes