ZEOLITES AS TEMPLATES FOR PREPARATION OF LARGE-RING COMPOUNDS - INTRAMOLECULAR PHOTOCYCLOADDITION OF DIARYL COMPOUNDS

The fluorescence spectra and photocycloadditions of poly(ethylene glyc ol) labeled at the chain terminal with 2-naphthyl groups (N-P-n-N) or one 9-anthryl and one l-naphthyl groups (N-P-n-A) and polymethylene en d-labeled with two 2-naphthyl groups (N-M-n-N) or two 9-anthryl groups (A-M-n-A) included in NaY zeolite have been investigated. At loading levels less than 1 guest molecule per 10 supercages of zeolite, N-P-n- N, N-M-n-N, and A-M-n-A exclusively exhibit intramolecular excimer emi ssion. Selective excitation of the naphthyl moiety in N-P-n-A mainly r esults in emission from the anthryl chromophore and intramolecular exc iplex fluorescence. Irradiation of the above compounds leads to format ion of intramolecular photocyclomers to the exclusion of intermolecula r products. These results are explained in terms of the compartmentali zation of the guest molecules in the supercages of NaY zeolite. Thus, this work demonstrates the utility of micropores of zeolites to promot e the formation of large-ring compounds in synthetically useful quanti ties. Of particular interest is the enhanced formation of the cross-ph otocyclomers of anthracene and naphthalene derivatives (a process not observed in homogeneous solution) in high yields.