= Solution
The alcohol first attacks CDI, forming an activated O-carbonylimidazole derivative. Its departure gives the resonance-stabilized propargyl/allenyl cation
$$
\mathrm{Ar-C^+(CF_3)-C{\equiv}C-Ph
\leftrightarrow Ar-C(CF_3)=C=C^+(Ph)}.
$$
The ortho amino nitrogen attacks the \b[central carbon of the allenyl system], closing the five-membered indole ring. Electron redistribution and loss of the N-H proton establish the indole aromatic system while leaving a <carbene> at the original distal, phenyl-bearing alkyne carbon.
For atom tracking, the original carbinol carbon becomes indole C3, the proximal alkyne carbon becomes C2, and the distal $\mathrm{C(Ph)}$ becomes the exocyclic <carbene>. Attack at the distal alkyne carbon would make a six-membered ring and cannot give the displayed skeleton. This carbene-based rearrangement has a primary experimental precedent.<Rapid assembly of substituted dihydrocycloheptapyrroloindoles by Lisa F. Frey and colleagues>{ref}
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