At dawn we did not sleep. Contribution to the dawn of functional group translocation: ortho → para 1,3-acyl migration of 2-fluoroacetophenone

Abstract

Abstract Functional Group Translocation (FGT) was defined ( Chem. Soc. Rev. 2026) as a transformation in which the molecular formula, the identity of the functional group, and the carbon framework remain unchanged, while only the bonding position of the functional group is altered, claiming: 1,2-migrations dominate the FGT field, while predictable long-range [1,n] translocations are still rare. The Brief Report throws doubt on the rarity of long-range FGT. We report the ortho → para (1,3)-acyl migration of 2-fluoroacetophenone (2FPhAc), a simple case (not polycyclic aromatic) of Friedel-Crafts acyl rearrangement. Treatment of 2FPhAc with polyphosphoric acid at 220 °C for 30 min gave the following distribution of the constitutional isomers of fluoroacetophenone: 67% 2-fluoroacetophenone (2FPhAc), 0% 3-fluoroacetophenone (3FPhAc), 33% 4-fluoroacetophenone (4FPhAc). The latter was purified by preparative gas chromatography. In spite of the relative low yield of the rearrangement product 4FPhAc, much smaller than that of the starting isomer 2FPhAc, and the very high temperature, for principal reasons, the formation of the rearranged isomer, a long-range (1,3)-acyl migration FGT, widens the scope of Friedel-Crafts acyl rearrangements, including an ortho → para rearrangement.