Table 1. Proton NMR data for PPBF and methylated analogs.

Designation	R	a [6H]	b [2H]	c [3H]	d [3H]	e [3H]	f [3H]	Aromatic
PPBF	NA	1.49	2.95	2.56	2.33	2.14	NA	Complex [5H]
4-methyl PPBF	para-CH3	1.49	2.96	2.56	2.30	2.14	2.34	7.07, 6.91 [4H]
3-methyl PPBF	meta-CH3	1.49	2.96	2.57	2.31	2.14	2.36	7.15, 7.03, 6.92, 6.78
2-methyl PPBF	ortho-CH3	1.50	2.98	2.57	2.31	2.15	2.36	7.23, 7.13, 7.05, 6.76

¹H chemical shifts (ppm) for PPBF analogs were measured in deuterated chlorofom at 24.8°C. The spectrum of PPBF was characterized by the appearance of signals consistent with the 2,2,4,6,7-pentamethyl-dihydrobenzofuran nucleus linked to an isolated and otherwise unsubstituted phenyl ring. In particular, there was a resonance for the pair of 2,2 methyl groups (1.49 ppm; singlet; 6H), three additional resonances for the 4-, 6-, and 7-methyl groups (2.56, 2.33, 2.14 ppm; singlets; 3 × 3H) and a complex multiplet of aromatic signals (7.02-7.35 ppm) partially obscured by the residual CHCl₃ resonance at 7.26 ppm, consistent with the isolated phenyl ring. NA, not applicable. R refers to the position at any methyl substitutions on the phenyl ring.