Fig. 2: Construction of phosphine-containing 1,1,3-trisubstituted cyclobutane scaffolds^a,b.

^aConditions A: 0.2 mmol BCB 1, 1.2 equiv. diphenyl phosphine, and 10 mol% CuCl in 2.0 mL THF at 60 °C for 24 h. ^bIsolated yield. ^c1.0 mmol scale.