with hcl 1 n 30 ml and a saturated aqueous solution of nahco 3 30 ml the organic phase was then dried over magnesium sulphate filtered and evaporated to afford the desired intermediate as a colourless oil this was immediately dissolved in dry acetone 10 ml and potassium thioacetate 1 71 g 15 0 mmol was added the reaction was then heated to reflux until none of the mesylate intermediate could be detected by 1 h nmr spectroscopic analysis 12 28 h the mixture was then filtered the filtrate evaporated and the crude purified by flash chromatography following the general procedure outlined above the product was isolated in 74 yield as a colourless oil tlc hexane ch 2 cl 2 7 3 v v r f 0 42 nmr 400 mhz cdcl 3 u03b47 22 7 35 m 5h 4 44 d j 8 0 hz 1h 2 32 s 3h 2 08 2 22 m 1h 1 06 d j 6 5 hz 3h 0 89 d j 6 5 hz 3h 13 c nmr 100 mhz cdcl 3 u03b4194 2 q 141 2 q 127 8 127 7 126 5 54 8 33 1 30 2 20 3 20 1 hrms m z m na calcd for c 12 h 16 onas 231 0820 found 231 0819 following the general procedure the product was isolated in 69 yield as a colourless oil tlc hexane ch 2 cl 2 7 3 v v r f 0 34 1 h nmr 400 mhz cdcl 3 u03b48 09 d j 8 5 hz 1h 7 89 d j 8 0 hz 1h 7 81 d j 8 5 hz 1h 7 61 7 43 m 4h 5 56 q.