[13412-55-0] · C20H15NO · Triphenylacetonitrile N-Oxide · (MW 285.36)
Physical Data: mp 152-153 °C.2
Solubility: sol benzene, dioxane.
Form Supplied in: colorless solid; not commercially available.
Analysis of Reagent Purity: IR 2280, 1320 cm-1; the corresponding isocyanate, the primary decomposition product, has a strong band at 2250 cm-1.
Preparative Methods: usually prepared2,3 by treatment of silver fulminate with triphenylmethyl chloride. The compound is reported4 to be readily available from triphenylacetaldehyde oxime by treatment with bromine in an NaOH/H2O/CCl4 mixture at 0 °C, but no experimental details are provided.
Purification: recrystallization from a minimum amount of benzene.
Handling, Storage, and Precautions: if the reagent is being prepared from silver fulminate, extreme caution should be exercised due to the shock sensitivity. Unlike other nitrile oxides, which are usually generated in situ, triphenylacetonitrile oxide is a fairly stable solid. Upon heating it rearranges to triphenylmethyl isocyanate. Introducing a 3- or 4-trifluoromethyl group dramatically increases the proclivity towards rearrangement.2
Like other nitrile oxides (see Acetonitrile N-Oxide) this reagent is useful for 1,3-dipolar cycloaddition reactions. Alkenes give 3-triphenylmethyl-D2-isoxazolines containing a labile Ph3C group which may be used to trigger other events. For example, photolysis of 3-triphenylmethyl-D2-isoxazolines fragments the heterocycle, presumably by homolysis of the Ph3C-C bond (eq 1).4 The triphenylmethyl group of 3-triphenylmethyl-D2-isoxazolines is also the key to a novel preparation of cyclic ethers (eq 2).5 The regiochemistry of dipolar cycloadditions of nitrile oxides containing bulky substituents has been studied.6
Dallas K. Bates
Michigan Technological University, Houghton, MI, USA