β-phenethylamines are oft-encountered structural motifs in biologically active compounds,1 including dopamine receptor agonists,2 various enzyme inhibitors,3 and are particularly prevalent in small-molecule therapeutics for central nervous system disorders,2b, 4 opioid receptor drugs,5 and analgesics.6 Fragment-based drug discovery campaigns,3a which rely on elucidation of quantitative structure–activity relationships, demand modular synthetic methods to diversify all the constituent...