Activation of a dienediyne model of neocarzinostatin chromophore through an acid mediated solvolysis. Evidence for a new cyclization mode of enyne[3]cumulenes

Article abstract of DOI:10.1016/0040-4039(93)88101-N

When treated with 0.1 equiv. of triflic acid, a solution of the Z-configurated dienediyne 19 in a 2:3 mixture of tert-BUSH and CH ₂Cl₂ furnished the brightly yellow enyne[3]cumulene 20 through a S_N-reaction. 20 reacted at room temperature through a Saito-Myers cyclization to the substituted styrenes 31 and 24 and through an unprecedented cycloisomerization to the anthracene 25.