Corresponding aromatic compound 1a–d (1 mmol) and nitromethane 2
(0.244 g, 4 mmol) in PPA (3–4 g) was stirred at 90–95 C for 5–8 h (Table 2). The
reaction mixture was poured in water (30 mL) with intense stirring and then cooled
to 0 C, and sodium nitrite (0.069 g, 1 mmol) was added. The reaction mixture was
stirred at this temperature for 15 min, and benzoic acids 7a–d were precipitated.
The resulting mixture was extracted by CH2Cl2 (1030mL). The solution was evaporated
under vacuum; the residue was purified by crystallization from water.
not sure if you would get delta 8 for doing this or if the reaction itself would protect the molecule
from isomerization.
still delta 8 THCa would be something would it not 
there are other methods on there too.