| The non-4(E)-en-6-yn-1-ol 16 can regiospecifically and stereoselectively add tri-n-butyltin hydride. The 7-tri-n-butylstannyl-4,6-nonadien-1-ols 20a (4E,6Z) and 20b (4E,6E) can be separated by liquid chromatography and stereospecifically hydrolyzed to the 4,6-nonadien-1-ols 15a, (4E,6E), and 15b, (4E,6Z).;6-(Ethyl-3-(1-trimethylsiloxypropan-3-yl)-1,2-dioxane, 11, is readily desilylated by fluoride ion, but the peroxide is not cleaved readily by base. Sensitized photolysis leads to chalcogran, 8, in 16% yield. Catalytic hydrogenation of 6-ethyl-3-(1-trimethylsiloxy-propan-3-yl)-1,2-diox-4-ene, 27, under slightly acidic conditions, followed by desilylation under thermal conditions leads to chalcogran formation in 16% yield. The second most abundant product is speculated to be 1-ethyl-2,9-dioxabicyclo 4.2.1 nonane, 43.;The synthesis of 5-methyl-5-octenal, 14, is reported. The hydrogen peroxide-boron trifluoride cyclization will occur even with 30% hydrogen peroxide, but over-oxidation and secondary rearrangements of 1-methyl-6-ethyl-7,8-dioxabicyclo- 3.2.1 octane, 13, prevents its isolation. Only exo-brevicomin, 6, was identified by 300 MHz NMR in the crude reaction.;Trimethylsilyl iodide cleavage of THF followed by a Wittig reaction offers a quick route to the silylated 4,6-nonadien-1-ols 22b (4Z,6E) and 22a (4E,6E). Both 22a and 22b yield the cis-endoperoxide, 27 when reacted with singlet oxygen. Platinum oxide catalyst in base-washed ethyl acetate allows hydrogenation of 6-ethyl-3-(1-trimethyl-siloxypropan-3-yl)-1,2-diox-4-ene, 27, to 6-ethyl-3-(1-trimethylsiloxypropan-3-yl)-1,2-dioxane, 11. |
