= Solution
The product is \b[N-\[5-(2-chloroacetyl)-2,3-dihydrobenzofuran-6-yl\]acetamide], with an aromatic $-\mathrm{COCH_2Cl}$ <substituent> at position 5. Substitution of one aromatic <hydrogen> by $\mathrm{C_2H_2ClO}$ gives the stated molecular formula. This positional assignment also agrees with the isolated intermediate reported in the original process study.<Process Development to Synthesize SGD-11275 Utilizing a Pd-Catalyzed Acetamide Arylation and Gallium-Mediated Friedel-Crafts Acylation by Tristan M. McGinnis and others>[Experimental section, N-(5-(2-chloroacetyl)-2,3-dihydrobenzofuran-6-yl)acetamide]{ref}
<GaCl3> activates <chloroacetyl chloride> by Lewis-acid coordination and chloride abstraction, represented by the acylium/contact-ion-pair limit $\mathrm{ClCH_2CO^+}$. The position-5 aromatic $\pi$ bond attacks the acyl <carbon>, giving a <Wheland intermediate>. Removal of the <proton> at that <carbon> restores <aromaticity>. Product–Lewis-acid coordination is reversed on work-up. The carbon-bound chlorine survives; the chlorine on the acyl <carbon> is the leaving group.
\Image[/past-exam-of-the-chemistry-b-course-of-the-university-of-cambridge/2025/paper-1-acylation.png]
{title=Position-5 chloroacetylation product and electron flow in Friedel-Crafts acylation}
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