Stereochemistry of photosolvolysis of (–)-1-phenylethyltrimethylammonium iodide in water and in methanol, and nucleophile capture ratios during photosolvolysis of some benzylammonium salts

Abstract

The photosolvolysis of (–)-1-phenylethyltrimethylammonium iodide in water or methanol is characterised by extensive racemisation accompanied by some net configurational inversion, a result similar to that generally observed in thermal solvolysis via ion-pairs at chiral secondary centres. Recovered quaternary salt from the photolysis in water is only slightly if at all racemised, while likewise there is no observable epimerisation at nitrogen in recovered benzylammonium salts following photolysis in methanol of suitable derivatives of camphidine, trans-decahydroquinoline, and 4-phenylpiperidine. A strong preference for formation of the methyl ether rather than the alcohol is exhibited on either photochemical or thermal solvolysis of 1-p-methoxyphenylethyltrimethylammonium iodide in aqueous methanol, but nucleophile capture ratios during photosolvolysis of simple benzyltrimethylammonium salts in this mixed solvent system are much lower.