1‐ and 2‐fluoroalkyl carboxylates

The 2‐fluoroalkyl esters (1–4) of carboxylic acids are readily accessible by the base‐catalyzed acylation of fluorohydrines. A two‐step procedure is required to prepare the 1‐fluoroalkyl esters (10–14, 16): conversion of alk‐1‐enyl carboxylates („ene esters”︁) into the 2‐bromo‐1‐fluoroalkyl esters 5–9, 15, 17–19 by simultaneous treatment with N‐bromosuccinimide and hydrogen fluoride followed by the reductive replacement of bromine by tributyltin hydride. Alka‐1,3‐dienyl carboxylates („diene esters”︁) undergo 1,4‐addition of bromine and fluorine. The resulting 4‐bromo‐1‐fluoroalk‐2‐enyl carboxylates 20–25 undergo a substitution reaction with sodium benzenesulfinate to afford the sulfones 26–28 or oxidation with dimethyl sulfoxide to yield the 4‐oxo derivatives 29–30.