A solution of N-isopropylcyclohexylamine (0.30 g) in dry tetrahydrofuran (5 ml) was stirred under argon and cooled to -78°. This was treated with a 2.5 M solution of n-butyl lithium in hexane (0.85 ml) and stirred for 10 minutes. A solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (9) (0.50 g) in tetrahydrofuran (5 ml) was added and after 5 minutes the anion was quenched by addition of methyl iodide (0.12 ml). After a period of 10 minutes the reaction vessel was transferred to an ice bath and a further 10 minutes later the reaction was neutralized by addition of acetic acid (0.16 ml). The solvent was then stripped off and the residue partitioned between ethyl acetate and brine. The ethyl acetate solution was separated, washed with brine and dried over sodium sulphate. The product was subjected to careful column chromatography on silica gel 60 eluting with cyclohexane/ethyl acetate mixtures grading from 1:1 to 3:7. This gave 4-allyl-3-methyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (38) (0.10 g, 19%); νmax (CHCl3) 3000, 1735 and 1610 cm-1. Running closely behind this was recovered starting phosphorane (9) (0.17 g. 33%).
