Catalyses Lindlar

The synthesis of (Z)-2-methoxy-5-hexadecenoic acid (10) was done in a similar fashion, but it first required the preparation of (Z)-4-pentadecenal. In this case, the aldehyde was made starting with commercially available 1-dodecyne that was coupled with 2-(2-bromoethyl)-l,3-dioxolane and n-BuLi in tetrahydrofuran-hexamethylphosphoramide, resulting in the expected 2-(3-tetradecyne)-1,3-dioxolane, Fig. (13). Subsequent catalytic hydrogenation using Lindlar s catalyst afforded the expected 2-(3-tetradecenyl)-l,3-dioxolane. The dioxolane was removed with 5% HC1 in acetone-water (1 1), and the equilibrium favored (Z)-4-pentadecenal. Addition of trimethylsilyl cyanide to (Z)-4-pentadecenal under triethylamine catalysis as described by Mukaiyama for other shorter-chain analogues [36] resulted in 2-trimethylsilyloxy-5-hexadecenonitrile. Under basic conditions the... 

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