INVESTIGATION OF THE PHOTO-FRIES REARRANGEMENTS OF 2 2-NAPHTHYL ALKANOATES BY EXPERIMENT AND THEORY - COMPARISON WITH THE ACID-CATALYZED REACTIONS

A detailed investigation of the photochemistry of a-naphthyl acetate ( 1a) and 2-naphthyl myristate (1b) has been conducted under a variety o f conditions. Factors related to the reactions such as temperature and solvent type have been explored. The results, most easily interpreted by photo-Fries type processes, are contrasted with those from the Lew is-acid catalyzed (dark) Fries reactions of 1a. They are also compared to the predictions of semiempirical and ab initio calculations using 2-naphthyl propanoate (1c) and species derived from it as models. Unsu ccessful triplet sensitization experiments with benzophenone and calcu lations point to the excited singlet states of 1 as the immediate prec ursor to the acyl/2-naphthoxy radical pairs that recombine to form ket o intermediates 2, reform 1, or diffuse apart and eventually yield 2-n aphthol (4); enolization of 2 results in the isolated rearrangement pr oducts, n-acyl-2-naphthols (n-3). Static and dynamic fluorescence stud ies provide some insights into the nature of the lysis process. Irradi ation of a mixture of appropriately labeled derivatives of 1 led to no ne of the expected ''cross-over'' products, indicating that the interm ediates 2 arise from recombination of radical pairs from the same pare nt molecule. Irradiation of 1b in ethanol and 1-octanol provides no ev idence for the intermediacy of dodecylketene and supports out-of-cage mechanisms as the exclusive source of 4. There are indications of subt le solvent effects and a conformational dependence on the distribution of photoproducts.