Larger rings transannular effects

For larger rings, 8c and 8d, the differences in chemical shifts of jp-carbons are about 1 p.p.m. The larger deshielding of the jp-carbons of 8b can be explained in terms of the diamagnetic anisotropy effect of the transannularly positioned diacetylene group, which was estimated by Roberts and coworkers , in addition to the ring strain effect. 

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