Guided by theoretical predictions, the rotational spectrum of fluoroiodomethane, CH(2)FI, has been recorded and assigned. Accurate values are reported for the ground-state rotational constants, all quartic, sextic, and two octic centrifugal-distortion constants. The hyperfine structure of the rotational spectrum was thoroughly investigated using a Fourier-transform microwave spectrometer and the Lamb-dip technique in the millimeter-/submillimeter-wave region, thus allowing the accurate determination of the complete iodine quadrupole-coupling tensor and of the diagonal elements of the iodine spin-rotation tensor. Relativistic effects turned out to be essential for the accurate theoretical prediction of the dipole moment and quadrupole-coupling constants and were accounted for by direct perturbation theory and a spin-free four-component treatment based on the Dirac-Coulomb Hamiltonian. The relativistic corrections to the dipole moment amount to up to 34% and to the iodine quadrupole-coupling tensor to about 15-16% of the total values.
Fluoromethylation. Fluoroiodomethane can react with var-ious nucleophiles (phenols, benzoic acid derivatives, amines,amides, and thiol derivatives) to give the correspondingfluoromethylated products (eq 3).2,3However, reproducibilityproblems have been observed since some of the fluoromethylatedproducts are unstable.
Fluoromethyl radical can be generated from the photolysis of
fluoroiodomethane.
6
In the presence of alkenes, multiple addition
products are obtained. However, the selectivities observed are not
high enough to be synthetically useful.
A palladium-mediated Suzuki–Miyaura-type fluoromethyl-
ation has been developed by rapid trapping of fluoroiodomethane
with an excess amount of pinacol phenylboronate ester (eq 4).
7
Fluoromethylation with [
18
F]fluoromethyliodide is of interest
in radiochemistry for the preparation of [
18
F]-labeled pharma-
ceuticals. The latter are used for positron emission tomography
(PET) due, in particular, to the longer half-life of fluorine-18
relative to carbon-11 (109.8 min vs. 20.4 min). A number of novel
Fluoromethyl radical can be generated from the photolysis offluoroiodomethane.6In the presence of alkenes, multiple additionproducts are obtained. However, the selectivities observed are nothigh enough to be synthetically useful.A palladium-mediated Suzuki–Miyaura-type fluoromethyl-ation has been developed by rapid trapping of fluoroiodomethanewith an excess amount of pinacol phenylboronate ester (eq 4).7Fluoromethylation with [18F]fluoromethyliodide is of interestin radiochemistry for the preparation of [18F]-labeled pharma-ceuticals. The latter are used for positron emission tomography(PET) due, in particular, to the longer half-life of fluorine-18relative to carbon-11 (109.8 min vs. 20.4 min). A number of novel PET tracers have been prepared (eq 5) by fluoromethylation with[18F]fluoromethyliodide.8–11
Preparation of Fluorophosphonium Salts En Route toTerminal Fluoroalkenes. Fluoroiodomethane reacts with triph-enylphosphine to form the stable phosphonium salt A, whichcan undergo a dehydrohalogenation with n-butyllithium in THFat −78◦C (eq 6). The in situ generated phosphorane B can thenreact with aldehydes and ketones to give the terminal monofluoro-alkenes.1,12–14While the reaction proceeds efficiently (52–80%yield for the aldehydes), a mixture of trans and cis isomers areobtained with low selectivity.
Synthesis of Rhenium α-Fluoromethyl Complex. The
strongly nucleophilic carbonylmetallate Na
+
[(CO)
5
Re]
−
was
treated with fluoroiodomethane to afford the first rhenium
α-fluoromethyl complex in 73% yield (eq 7).
15
Synthesis of Rhenium α-Fluoromethyl Complex. Thestrongly nucleophilic carbonylmetallate Na+[(CO)5Re]−wastreated with fluoroiodomethane to afford the first rheniumα-fluoromethyl complex in 73% yield (eq 7).15
