engleski

Novel geometry polynorbornane scaffolds for chromophore linkage and spacing

Several types of carbonyl p-bonds (aldehydes, aryl-fused ring COs) have been shown to act as dipolarophiles in a [4p+2p] reaction with those 1, 3-dipoles formed by the ring-opening of ester-activated cyclobutene epoxides. This new reaction produced cycloadducts incorporating the CO bond into a rigid polyalicyclic scaffold and positioning the attached chromophore stereoselectively, viz single bond attachment with aldehydes, spiro-fusion with ring-ketones. A selection of chromophore-spacer-chromophore dyads have been prepared in which combinations of chromophores (1, 4-dimethoxynaphthalene, 1, 10-phenanthroline, 3, 6-di(4-pyridyl)pyridazine, anthracene, porphyrins) have been separated by up to 7s-bonds (and more in principle) and related one to the other in novel geometrical orientations. Preliminary results involving cyclic a-diones and cyclic triones as 2p-reagents has considerably improved the range of unsymmetrical dyads available using this COCE coupling protocol ; building sequences involving ninhydrin being especially versatile. Other BLOCK methods for the preparation of mixed chromophore dyads have been reviewed and several new norbornene building BLOCKs described.

Carbonyls, cycloaddition, 1, 3-dipole

nije evidentirano