Aromaticities of Five Membered Heterocycles through Dimethyldihydropyrenes Probe by Magnetic and Geometric Criteria

Table 2

¹H NMR chemical shifts (calculated) of dihydropyrenes and nonaromatic reference models, % aromaticities of five membered heterocycles, calculated through (5).

Entry	Heterocycles	DHP	δ	Nonaromatic reference	δ	% bond fixation	% aromaticity
1		1	−6.29
2	Benzene	3	−1.91		−5.45	53.9	100
3	Pyrrole	12	−3.31	14	−5.62	34.3	63.6
4	Thiophene	18	−4.16	28	−6.08	26.9	49.5
5	Oxazole	20	−4.8	29	−5.88	15.4	28.6
6	Isoxazole	21	−3.51	30	−5.65	31.6	58.9
7	Thiazole	22	−4.59	31	−5.98	19.6	36.3
8	Isothiazole	23	−3.99	32	−6.05	31.5	58.5
9	Pyrazole	24	−2.52	33	−5.89	48.1	89.2
10	Imidazole	25	−3.81	34	−5.51	25.6	49.6
11	Oxadiazole	26	−3.59	35	−5.63	30.5	56.6
12	Triazole	27	−2.91	36	−5.83	44.9	83.3