Does carboxyl group interfere with reaction of 2-carboxybenzaldehyde with NaCN/HCl?

The aldehyde group of [2-carboxybenzaldehyde](https://en.wikipedia.org/wiki/2-Carboxybenzaldehyde) reacts with $\ce{NaCN/HCl}$ forming [cyanohydrin](https://en.wikipedia.org/wiki/Cyanohydrin). Does the carboxyl group remain intact? Does it react separately or with the cyanohydrin?


I suspect possible intervention of the lone pair from the $\ce{-CN}$ group to form an aromatic ring. Does it (or something else) happen or not?




@Waylander's suggestion that 3-cyanophthalide [3-oxo-1,3-dihydroisobenzofuran-1-carbonitrile] **6** is expected as the product of the reaction is well-reasoned. This reaction has been reported by Hesse, et al.[[1]](https://onlinelibrary.wiley.com/doi/10.1002/hlca.200390058) The reaction of aldehyde **1** in the presence of sufficient aq. HCl to generate HCN and enough to act as a catalyst for the reaction does not provide **6** directly. The cyanophthalide **6** is not formed under the conditions employed but, seemingly, the cyanohydrin **2**, which was isolated by extraction with ethyl acetate. The crude material was lactonized with dicyclohexylcarbodiimide [DCC] **3** as shown in the steps **2** $\rightarrow$ **6**.


![](https://i.stack.imgur.com/gedU2.jpg)
1. Y. Li, A. Linden, M. Hesse, [*Helv. Chim. Acta*, **2003**, *86*, 579](https://onlinelibrary.wiley.com/doi/10.1002/hlca.200390058).


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