A method for the determination of substitution pattern in coumarins using a lanthanide shift reagent
Abstract
The n.m.r. shift reagent tris-(7,7-dimethyl-1,1,1,2,2,3,3-heptafluoro-octane-4,6-dionato)europium(III)[Eu(fod)3] complexes with the carbonyl oxygen of coumarins so that all shifts can be related to a position for the europium atom in the plane of the ring and on the 3-H side of the CO bond; relatively large shifts are produced for an 8-substituent, and information about other substituent positions can be obtained.