Esterification between carboxylic acid and alcohol^ab.

^aPath A reaction conditions: 1 (0.5 mmol), 2 (0.6 mmol), I₂ (0.5 mmol), KH₂PO₂ (0.5 mmol) and anhydrous sodium sulfate (0.4 g) at 25 Hz in mixer mill, using two stainless steel balls (ϕ = 1.2 cm, Φ_MB = 0.036) in 50 mL stainless steel vial. Yield based on 1.

^bPath B reaction conditions: 1 (0.5 mmol), 2 (0.6 mmol), KI (0.75 mmol), P(OEt)₃ (0.5 mmol) and anhydrous sodium sulfate (0.4 g) at 25 Hz in mixer mill, using two stainless steel balls (ϕ = 1.2 cm, Φ_MB = 0.036) in 50 mL stainless steel vial.

^c1 (2.0 mmol).

^d2 (1.8 mmol).