The reaction of N-isopropylallenimine (1) with several organic azides has been examined. Phenyl azide gives a mixture of triazole 3 and amidine 7. p-Toluenesulfonyl azide reacts with 1 to give only amidine 11; likewise tertbutyl and ethyl azidoformate give 12 and 13, respectively. Reaction of 12 with dry HCl gives N-isopropyl-P-lactamimide (14). The formation of the amidines and triazole 3 is rationalized in terms of triazoline intermediates.We have recently reported on the highly strained l-azaspiropentane s t r u c t~r e .~~~ This novel heterocyclic system was obtained by photochemical decomposition of triazoline precursors derived from thermal cycloaddition of phenyl azide t o methylenecyclopropanes (see eq 1). We now report on our attempts to extend this synthetic sequence to allenimine 1 in hopes of effecting conversion to a 1,4-diazaspiropentane (2).N-Isopropylallenimine (1) reacts slowly with phenyl azide to yield l-phenyl-5-(N-isopropylaminomethyl)-1,2,3-triazole (3) as the major product. The NMR of 3 shows, among other features, a sharp singlet for the aliphatic methylene group and a one-proton singlet a t 6 7.66 for the triazole ring proton. The uv spectrum of 3 displays a maximum a t 228 nm, supporting assignment as a &substi-tuted l-phenyl-1,2,3-triazole. Substitution at the 4 position of the triazole ring is known to shift the uv maximum of the parent l-phenyl-1,2,3-triazole (4) (248 nm) to longer wavelength, whereas substitution at the 5 position causes a shift to shorter ~a v e l e n g t h .~ l3C NMR confirms the 5-substituted l-phenyl-1.2,3-triazole structure for 3; the chemical shifts of the triazole and phenyl carbons of 3 and 4 are listed in Table I. The C-5 carbon of the triazole ring in 3 is shifted downfield 14.5 ppm relative to 4, indicating substitution a t that position, whereas the C-4 carbon experiences only a slight upfield shift. An important indicator of substitution a t the 5 position of 3 is the ca. 4.5-ppm downfield shift of the phenyl ortho carbons relative to 4. This is an effect seen in 5-substituted t r i a~o l e s ,~ presumably resulting from steric interaction between the substituents. Table I I3C Spectra of Triazolesa Compd C -4 c-5 N-Ph o-Ph m-Ph b-Ph 3 133.3 136.3 136.6 124.7 129.3 129.3 4 134.0 121.7 136.6 120.2 129.4 128.4 a Chemical shifts in parts per million relative to internal Mersi.An authentic sample of 3 was obtained by independent synthesis. Phenyl azide reacts with N-isopropylpropargylamine to yield a 60:40 mixture of 4-and 5-(N-isopropylaminornethyl)-l-phenyl-1,2,3-triazole (5 and 3). Each of the NMR signals of the major isomer appears a t lower field than the corresponding one of the minor isomer. The triazole ring protons are particularly characteristic of th'is, appearing at 6 7.85 for 5 and S 7.66 for 3. A sample of pure 3 was obtained by column chromatography and shown to be identical with the product obtained from the reaction of 1 with phenyl azide. The formation of 3 is rationalized by the addition of phenyl azide to 1 to give triazoline 6 as shown in...
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