Aza-di-7T-methane rearrangements

Specific imine derivatives of otherwise reluctant (see preceding section) 3.T-unsaturated aldehydes and ketones are again photochemically reactive and cyclize in high yields when irradiated in the presence of a triplet sensitizer, they undergo the aza-di-7T-methane rearrangement, typical examples of which are shown for (31) —> (32) (R = alkyl or phenyl). ... 

I, 743,1987 (b) Armesto, D., Horspool. W. M., Langa, R, and Perez-Ossorio, R., Substitution effects on the aza-di-7t-methane rearrangement of imines, /. Chem. Soc., Perkin Trans. 2, 1039,1987 (c) Armesto, D., Horspool, W.M., and Langa, R, The aza-di-Jt-methane rearrangement of l-aryl-4,4-dimethyl-6,6-diphenyl-2-azahexa-2,5-dienes. The influence of substituents on the N-benzyl group, /. Chem. Soc., Perkin Trans. 2, 903, 1989 (d) Armesto, D., Horspool, W.M., Mancheno, M.J., and Ortiz, M.J., Chemically efficient aza-di-Jt-methane photoreactivity with novel stable derivatives of P,y-unsaturated compounds, /. Chem. Soc., Perkin Trans. 1, 2325, 1992, and papers cited in Reference 37. 

Despite the large number of studies carried out on the DPM and ODPM rearrangements since the discovery of the DPM reaction in 1967 by Zimmerman et al., it was necessary to wait 10 years before the reaction was extended to other 1,4-unsaturated systems, particularly to CN double bond derivatives. The first example of a l-aza-di-7t-methane rearrangement (1-ADPM) was reported by Nitta et al. in a study of the photoreactivity of highly constrained tricyclic oximes. However, the reaction was limited to... 

The di-7t-methane rearrangement has also been observed in other 1,4-unsaturated systems, such as nitrogen-containing compounds.630,642 The corresponding aza-di-n-methane triplet-sensitized (sens) rearrangement of the ( , /-unsaturated imine 91 produces, inefficiently ( 0.01), a single product, cyclopropylmethanimine (92), which can subsequently be easily converted to an aldehyde by acid hydrolysis (Scheme 6.36).661... 

Within the area of SET-promoted di-7t-methane reactions, recent studies have shown that irradiation of 1-aza-1,4-dienes, such as 32, and the 1,4-diene 34, using AW-dimethylaniline (DMA) as electron-donor sensitizer, leads to production of the corresponding cyclopropane derivatives 33 and 35 resulting from 1-ADPM and DPM rearrangements, respectively, in reactions that take place via radical-anion intermediates (Sch. 11) [25]. 

McClure, C.K., Link, J.S., and Kiesshng, A., The oxa-di-7t-methane photochemical rearrangement of quinuchdinones, 1- and 2-aza-3-carboxybicyclo[2.2.2]oct-2-ene-5-ones Application to the synthesis of pyrrohzidine alkaloids. Abstract no. ORGN 480,221" ACS Meeting, San Diego, CA, 2001. 

---