2,2,4-Trimethyl-1,2,3,4-tetrahydroquinoline is a reagent in the synthesis of tetrahydroquinoline sensitizers used for dye-sensitized solar cells. 2,2,4-Trimethyl-1,2,3,4-tetrahydroquinoline is also a reagent in the preparation of tetra- and pentacyclic derivatives of phenothiazinium photosensitizers which are used as photoantimicrobial agents.