J. Org. Chem., Vol. 55, No. 11, 1990 3703 example, the chemical shifts of carbon C-5 are about 122 ppm for the 4-nitro isomers and 139 ppm for the 5-nitro isomers, whereas chemical shifts for carbon C-4 are 145 ppm for the 4-nitro and 133 ppm for the corresponding 5-nitro compounds. As can be seen from Table 11, the I3C chemical shift values for 3a-e are in exactly the same range, 122.0-122.7 ppm for the C-5 carbon and ...
