2,2 dimethylchroman 4 one 2 2,2-Dimethylchroman-4-ones 2 Article 2 Aryl 3-methyl-2-butenoate esters 2 Thermal 6π-electrocyclic reaction 2 aryl 3 methyl 2 butenoate ester 2 chemical reaction 2 chroman derivative 2 cyclization 2 cyclohexane 2 ester derivative 2 oxa-Michael cyclization 2 photo fries rearrangement 2 photo-Fries rearrangement 2 photochemistry 2 priority journal 2 reaction analysis 2 unclassified drug 2