1- and 2-fluoroalkyl carboxylates

The 2-fluoroalkyl esters, e.g. FCH2CH2CO2Me are readily accessible by the base-catalyzed acylation of fluorohydrines. A two-step procedure is required to prep. the 1-fluoroalkyl esters: conversion of alk-1-enyl carboxylates ("ene esters") into the 2-bromo-1-fluoroalkyl esters by simultaneous treatment with N-bromosuccinimide and HF followed by the reductive replacement of bromine by tributyltin hydride. Alka-1,3-dienyl carboxylates ("diene esters") undergo 1,4-addn. of bromine and fluorine. The resulting 4-bromo-1-fluoralk-2-enyl carboxylates undergo a substitution reaction with sodium benzenesulfinate to afford the sulfones or oxidn. with DMSO to yield the 4-oxo derivs. 2-Fluoroethanol was added to NaH followed by AcOH to give 2-fluoroacetate. 2-Bromo-1-fluoroethyl acetate (prepn. given) and Bu3SnH were kept at 90 Deg for 1 h to give 1-fluoroethyl acetate. [on SciFinder (R)]