2C-Bu, also known as 4-butyl-2,5-dimethoxyphenethylamine, is a serotonin receptor modulator of the phenethylamine and 2C families. It is the 2C analogue of the DOx derivative DOBU.
2C-Bu was not included in Alexander Shulgin's book PiHKAL (Phenethylamines I Have Known and Loved) and its properties and effects in humans are unknown.
2C-Bu is a potent and high-efficacy serotonin 5-HT<sub>2A</sub> receptor partial agonist, with an of 3.9 to 29nM and an of 71 to 93%.
2C-Bu follows 2C-D, 2C-E, and 2C-P in the homologous series of 4-alkylated 2C derivatives. Higher homologues of 2C-Bu including 2C-Am and 2C-Hx are also known and have been characterized.
2C-Bu has several notable skeletal isomers, including 2C-iBu, 2C-tBu, and 2C-sBu. 2C-iBu and 2C-tBu are both active and produce hallucinogen-type effects in animals and/or humans. This is in spite of 2C-tBu being predicted to be inactive and DOTB (the DOx analogue of 2C-tBu) being inactive as a hallucinogen in animals and humans. 2C-iBu may have reduced hallucinogenic potency than other 2C drugs and is being developed as a potential anti-inflammatory medication.
2C-Bu was said by Daniel Trachsel and colleagues in 2013 to be completely unknown. Subsequently, the drug was characterized in 2025.
2C-Bu is a controlled substance in Canada under phenethylamine blanket-ban language.