Addition of Cl<sub>2</sub>C:  to (−)-<i>O</i>-Menthyl Acrylate under Sonication−Phase-Transfer Catalysis. Efficient Synthesis of (+)- and (−)-(2-Chlorocyclopropyl)methanol MasunoMakoto N. YoungDouglas M. HoepkerAlexander C. SkepperColin K. MolinskiTadeusz F. 2005 Dichlorocyclopropanation of (−)-<i>O</i>-menthyl acrylate under conditions of phase-transfer catalysis (CHCl<sub>3</sub>, KOH, tetramethylammonium bromide), with sonication, gives excellent yields (85−94%) of the corresponding dichlorocyclopropanecarboxylate ester compared to thermal conditions (90 °C, 56%). No diastereoselectivity was observed, but one isomer was isolated pure by fractional crystallization. The measured kinetic isotope effect (initial rate (CHCl<sub>3</sub>)/rate (CDCl<sub>3</sub>) ∼1.7) suggests deprotonation of CHCl<sub>3</sub> as the rate-limiting step.