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 8-oxo derivatives 29-30.