L-Octyn

Acetylenic compounds have been described for inhibition in acid solutionsTypical inhibitors include 2-butyne-l,4-diol, l-hexyne-3-ol and 4-ethyl-l-octyne-3-ol. 

Ethyl S,4-deaadienoate (1). A 300-mL, round-bottomed flask equipped with a reflux condenser is charged with 12.1 g (0.096 mol) of l-octyn-3-ol (Note 1), 100 g (0.616 mol) of triethyl orthoacetate (Note 2), and 0.24 g (3.2 mmol) of propionic acid. The solution is heated at 140-150°C in an oil bath. Every 2 hr, the ethanol produced is removed under reduced pressure with a rotary evaporator, and then 10 g (0.062 mol) of triethyl orthoacetate and 0.024 g (0.32 mmol) of propionic acid are added. The mixture is heated until the starting material is consumed (6-8 hr) (Note 3). Excess triethyl orthoacetate is removed under reduced pressure (Note 4). The residue is distilled under reduced pressure to give 15.4-17.2 g (82-91t) of 1 (Note 5) as a clean oil, bp 80-85°C (0.3 mm). 

A molybdenum oxychloride-based catalyst system, MoOCl4- -Bu4Sn-EtOH, is more active than Mods ones. " In the polymerization of 1-chloro-l-octyne by the oxychloride-based catalyst, propagation rate is improved to be faster and MWD of the formed polymer is smaller. This ternary catalyst also induces living polymerization of... 

Asymmetric reduction of a, -acetylenic ketones 2 Detailed directions for reduction of l-octyne-3-one to (R)-l-octyne-3-ol with this reagent are available. This method has been used to reduce 10 other acetylenic ketones in >70% ee. 

Other hyperbranched polymers showed similar absorption and luminescence properties. Upon photoexcitation, the hb-PA solutions emitted deep-blue to blue-green lights, whose intensities were higher than that of poly(l-phenyl-l-octyne), a well-known highly emissive polyene. The PL efficiencies of the polymers varied with their molecular structures. Polymers hb-P(38-VI), hfo-P(45-V), hb-P(48-VI), M>-P(50-VI), fcfo-P(50-VII) and hb-P(59-VI) exhibited (P values higher than 70%, with hfc-P(50-VII) giving the highest value of 98%. 

The successful result of Murai et al. [49] is shown in (Eq. 26). When 1-trimethylsilylpropyne is used, the desired coupling product is obtained in excellent yield and the regiochemical and stereochemical outcome is perfect [49]. The E isomer is the predominant product. This result indicates that the addition of C-H bonds to the C-C triple bond proceeds with syn selectivity. In the case of the reaction with 1-trimethylsilyl-l-octyne, stereoselectivity is slightly decreased. This suggests that the small difference in steric bulkiness between methyl and hexyl groups affects the stereoselectivity. 

C. Excess 1 is destroyed by adding 22 mL (0.3 mol) of freshly distilled propionaldehyde and stirring for 1 hr at room temperature. Liberated a-pinene is then removed by vacuum (Note 7). Tetrahydrofuran, 200 mL, is added, followed by 150 mL of 3 M aqueous NaOH. Hydrogen peroxide (150 mL, 30%) is added dropwise (CAUTION Note 8). Oxidation is complete in 3 hr at 40°C. The reaction mixture is transferred to a separatory funnel and extracted with three 50-mL portions of ethyl ether. The ether layers are combined and dried with copious amounts of anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to give an oil. Distillation at 60-65°C (3.0 mm) yields 31 g (0.245 mol) of l-octyn-3-ol, 86% yield (Note 9). The distillation pot residue is a thick oil consisting for the most part of cis-l,5-cyclo-octanediol. An NMR lanthanide shift study showed the alcohol to be 93% (R) and 7% (S), 86% ee, (Note 10 and 11). 

This is the most convenient stage to remove a-p1nene since a-pinene and l-octyn-3-ol have similar boiling points, making separation by distillation difficult. Application of a 0.05-mm vacuum while the flask is warmed to 40°C for several hours will remove most of the a-pinene (0.4 mol, -63.5 ml.). Because of the volume of a-pinene, cold traps in the vacuum system may become plugged therefore the traps will have to be emptied several times. This provides a convenient method to recover liberated (t)-a-pinene. 

Optically pure (+)-l-octyn-3-ol may be obtained by recrystallization of the half acid phthalate with (+)-a-methylbenzyl amine (Aldrich Chemical Company). The half acid phthalate salt Is made by heating equal molar amounts of l-ocytn-3-ol and phthalic anhydride. This half acid phthalate derivative... 

Is a waxy solid which does not lend itself to recrystallization. Attempts to form crystalline salts of the phthalate derivative with achiral alkyl amines only lead to waxy solids or thick oils. The phthalic amine salt made with racemic l-octyn-3-ol requires 3-4 recrystal 1 Izations from methylene chloride to resolve enantiomers. The first recrystallization may take several days, with successive recrystal 1Izations becoming easier. If the 86% ee l-octyn-3-ol is used to make the phthalic amine salt only one facile recrystalHzation is needed to provide optically-pure alcohol. The pure amine salt melts at 132-134°C. The enantiomeric purity of the salt may be determined by NMR by observing the ethynyl hydrogen doublets at 6 2.48 (minor) and 2.52 (major) (CDClj solvent). 

The most popular methods of preparing optically active l-octyn-3-ol involve asymmetric reduction of l-octyn-3-one with optlcally-active alcohol complexes of lithium aluminum hydride or aluminum hydride. These methods give optical purities and chemical yields similar to the method reported above. A disadvantage of these metal-hydride methods is that some require exotic chiral alcohols that are not readily available in both enantiomeric forms. Other methods include optical resolution of the racemic propargyl alcohol (100 ee) (and Note 11) and microbial asymmetric hydrolysis of the propargyl acetates (-15% ee for l-heptyn-3-ol)... 

Cuprous bromide and l-octyn-3-ol were used as supplied by the Aldrich Chemical Company, Inc. Dioxane was dried over sodium/benzophenone and distilled, and diisopropylamine was distilled from barium oxide. 

One of the syntheses mentioned there started with 3-pyrazolidinone 236, which was protected as the benzyloxycarbonyl derivative 237 in order to obtain selective N-alkylation at position 8 yielding compound 238 after removal of the protecting group. Addition of the resulting amine 238 to l-octyne-3-one 239 formed the enone 240 with the complete diazaprostanoid skeleton. Katalytic... 

Carbometalation of silylalkynes. In the presence of this nickel-aluminum catalyst, methylmagnesium bromide adds to 1-trimethylsilyI-l-octyne (1) to give the cis-addition product 2, which isomerizes slowly to 3, The use of ethylmagnesium bromide results in reduction mainly to cis-1 -trimethylsilyl-1 -octene. The products 2 and 3, as expected, react with a variety of electrophiles to give di- and trisubstituted... 

Among silicon-containing acetylenes, 3-(trimethylsilyl)-l-octyne and its homologs are converted to high-molecular-weight polymers36 (Table 11). The MoCls-cocatalyst and Mo(CO)6—CC —hv systems afford the highest MW s. On the other hand, 1-silyl-acetylenes such as l-(trimethylsilyl)acetylene and l-(dimethylphenylsilyl)acetylene afford partly toluene-insoluble polymers 34,35), and Mn of the soluble fractions is no more than ca. 1 x 104. 

Chloro-l-alkynes (e.g., CICsCR R = n-Bu, n-C6H13, n-CgH17) polymerize with Mo catalysts in high yields. These monomers do not polymerize at all with W catalysts. As an example, Table 12 includes some results on the polymerization of 1-chloro-l-octyne 45). Both MoCls—cocatalyst and Mo(CO)6—CCI4—hv give polymers with Mw of 5 x 103-1 x 10 , while MoCls alone is less efficient. 

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