[CH3:1][C:2]1[CH2:7][CH2:6][C@H:5]([C:8]([OH:10])=O)[CH2:4][CH:3]=1.C1(C)C=CC=CC=1.[O-]P([O-])([O-])=O.[K+].[K+].[K+].C(Cl)(=O)C([Cl:29])=O>ClCCl.CN(C)C=O>[CH3:1][C:2]1[CH2:7][CH2:6][CH:5]([C:8]([Cl:29])=[O:10])[CH2:4][CH:3]=1
(1S)-4-Methyl-cyclohex-3-enecarboxylic acid (209 mg, 1.5 mmol), azeotropically dried by evaporation from toluene, was treated with potassium phosphate tribasic (383 mg, 1.8 mmol), suspended in dichloromethane (4 mL) and treated with dimethylformamide (2 drops). The reaction mixture was cooled to 0° C. and treated dropwise with oxalyl chloride (0.3 mL, 3.2 mmol). The reaction mixture was allowed to warm to ambient temperature while stirring for 2 h. After filtering the solids, the solution was concentrated, treated with hexanes and concentrated again to afford 4-methyl-cyclohex-3-enecarbonyl chloride (S) as a light yellow oil which was used immediately in the next step.
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