= Solution
Label the ynone carbons $\mathrm{Ar(OH)-CO-C_\alpha\equiv C_\beta-Ph}$. The N-oxide oxygen adds to the electrophilic $C_\beta$, giving an O-vinylated quinolinium species with an enolate-like nucleophilic $C_\alpha$.
The chain $C_\alpha-C_\beta-O-N-C2_{\rm quinoline}$ is now arranged for rearrangement: form a bond between $C_\alpha$ and quinoline C2 while cleaving N–O and forming the $C_\beta=O$ bond. This can be represented through a cyclic addition/rearrangement intermediate, followed by <proton transfer> and rearomatization. The resulting carbon skeleton is the heteroarylated 1,3-dicarbonyl system
$$
\mathrm{Ar(OH)-CO-CH(quinolin\!-\!2\!-\!yl)-CO-Ph}.
$$
Finally, the ortho phenolic oxygen attacks the distal <carbonyl>. <Cyclodehydration> forms the chromone ring and eliminates water. \b[The product is 2-phenyl-3-(quinolin-2-yl)chromen-4-one]. The original ynone <carbonyl> becomes the chromone 4-one, the phenyl-bearing alkyne carbon becomes C2, and the other alkyne carbon becomes C3 carrying the heteroaryl substituent.
This atom mapping explains both the new C–C bond and the loss of the N-oxide oxygen from the heteroarene; it is not a direct substitution on the phenyl ring.
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