Demethylation of 3-methoxy-4,5-dioxyphenylethylamine by heating with conc. HCl in a closed ampoule.
K. Hahn, Ber., 71, 2141 (1938) someone can try to find that.
and i've just scanned an article about purification of nicotinic acid by sublimation and decarboxylation it to pyridine by 1,5 hours of heating it at 320°C with CaO 1:1.2 in an ampoule.