Steric effects in enyne-allene thermolyses: Switch from the Myers-Saito reaction to the C2-C6-cyclization and DNA strand cleavage

Article abstract of DOI:10.1016/0040-4039(96)01758-3

The thermal reaction of enyne-allenes 1 with large substituents (tert.-butyl, trimethylsilyl) at the acetylene terminus leads to C²-C⁶ cyclization products presumably via an intermediate benzofulvene biradical, whereas with a hydrogen substituent the expected Myers-Saito cycloaromatization product is formed. Effective DNA strand scission can be observed when no intramolecular pathway is available.