[29885-95-8] · C9H10F3NO2 · N-Methylanilinium Trifluoroacetate · (MW 221.20)
Alternate Name: N-MATA.
Physical Data: mp 66.5 °C.
Solubility: insol pentane; sol THF; very sol MeCN.
Form Supplied in: crystalline white salt.
Analysis of Reagent Purity: elemental analysis.
Preparative Method: prepared from commercial grade Trifluoroacetic Acid and N-methylaniline (1:1) in dry Et2O under a nitrogen atmosphere with cooling in an ice-bath.1c
Purification: by sublimation and drying in a desiccator under vacuum at rt.
Handling, Storage, and Precautions: nonhygroscopic; not deliquescent; can be weighed in the air and stored for months under an inert atmosphere.
Ketones of various types form a-methylene ketones by direct methylene transfer from formaldehyde in the presence of N-MATA (eq 1).1,3,4
Both paraformaldehyde and trioxane can be used as the source of formaldehyde, but, with the latter, low yields of methylene ketones are sometimes obtained.3 With cyclohexanone, cyclopentanone, or aldehydes, preformation of the iminium intermediate [CH2=
Linear methyl ketones react at both the a- and a´-positions to give a mixture of regioisomeric methylene ketones (eq 4),1b as well as some divinyl ketone as a side product.
The reaction is not applicable to g- or d-lactones, or strained cyclic ketones such as norcamphor or cyclobutanone.1a,c
Deoxynucleoside methyl- and phenylphosphoramidites2 and also phosphorothioamidites5 are effectively activated by N-MATA for condensation with other suitably protected nucleosides to give deoxydinucleoside phosphates (eq 5).2 Phosphorodithioates5 or oligonucleotides (over 95%) have also been prepared in this manner using a polymer silica gel support.2
In the synthesis of deoxydinucleoside phosphorodithiolates, however, N-MATA causes excessive detritylation and the most satisfactory activator in this process is pyridinium tetrafluoroborate.5
Valerij A. Nikolaev
St. Petersburg State University, Russia