Amines photodimerization

While the photodimerization of bis(l-naphthylmethyl) ether was acknowledged somewhat earlier 39), the photodimers were first characterized and the quantum yield of the dimerization determined by Todesco et al. U2). Both the syn- and anti-photodimers were formed in roughly equal amounts, and the quantum yield for formation of the anti-dimer was independent of solvent. However, the quantum yields for formation of the syn-dimer and for excimer fluorescence were found to vary with solvent such that their sum was independent of solvent. The fact that irradiation of l,3-bis(l-naphthyl)-1-propanol yields only the syn-photodimer 113> indicates that the conformational properties of oxygen are largely responsible for anii-dimerization in the ether compound. The possibility of photodimerization was unfortunately not considered in the fluorescence studies of protonated bis (1-naphthylmethyl) amine 115>, l,3-bis(4-methoxy-l-naphthyl) propane 116>, and meso-bis( 1 -(1 -naphthyl-ethyl) ether 13). 

Ring formation takes place in the photodimerization of unsaturated ethers and amines, such as phenyl vinyl ether and vinyl carbazole (Eq. 32). 

Paquette s work at Upjohn generated many examples of photodimerization and also subsequent reactions of the photoproducts, primarily hydrogenation, lithium aluminum hydride reduction, and quatemization of the resulting amines to give 90 and related products (Figure 29). Much of this chemistry can be found in the patent... 

Figure 29. Photodimerization products are transformed to amines and quaternary ammonium salts, several of which were discovered to have bioactivity at Upjohn.

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