2-Propynylic acetates

Silver trifluoroacetate is a suitable catalyst for various cationic rearrangements involving multiple carbon-carbon bonds [49 5(1] In the presence of silver trifluoroacetate, 2 propynyl acetates rearrange to the butadienyl acetates to give dienes that are useful in Diels-Alder reactions [49] (equation 22)... 

Butadienyl acetates. These useful Diels-Aldcr dienes (2) can be obtained by isomerization of 2-propynylic acetates (1) with this silver salt or with PdCl2. The substrates (1) rearrange to allcnyl acetates (3) with CuCl. ... 

Reactions with 1-propynylic acetates. R2CUL1 reacts with 2-propynylic acetates to give allenes as major products (equation I). 

Nilsson and Hacksell isolated 2,5-dimethyl-4-phenyloxazole 245 (Ri = CH3, R2 = CeHs) as the only product from methylation of N-(l-phenyl-2-propynyl)acet-amide 244 (Ri = CH3, R2 = CeHs). The authors found that propargyl amides could be cyclized to 2,5-disubstituted and 2,4,5-trisubstituted oxazoles (Scheme 1.67). Thus a propargyl alcohol 243 was converted to the corresponding amide 244 in... 

Example 1-Propynyl acetate has nn = 1.4187 and density = 0.9982 at 20°C the molecular weight is 98.102. From the Lorentz and Lorenz equation,... 

Particularly significant results have been obtained in the oxidative carbonylation of simple and functionalized alkynes. Thus, the PdI2/KI-catalyzed oxidative carbonylation of simple alkyl- or arylacetylenes, as well as of propy-nyl alcohol and propynyl acetate, carried out in alcoholic solvents under mild conditions (15-25 atm of CO, 4-9 atm of air, 25-80 °C), led to the formation of maleic derivatives (together with small amounts of fumaric derivatives) and 5,5-dialkoxyfuran-2(5H)-ones, in high yields and with unprecedented catalytic efficiencies for this kind of reaction (up to ca. 4000 mol of product... 

Diastereoselective cleavage of propynyl acetals of enantiomeric pure diols with organocopper(I) reagents leads to alkoxyallenes with high diastereomeric purity, in which the chiral auxiliary is included... 

Liang et al. reported a PtCla-catalyzed transformation of 3-(2-alkyl)phenyl-propynyl acetate 130 to prepare naphthalenyl acetate 131 (Scheme 50) [45]. The electrophihc Pt-allene complexes formed in situ worked as hydride acceptors. Mechanistically, the Pt(Il)-promoted [l,3]-OAc shift leads to the formation of platinum-activated allenyl ester 1, which undergoes a [l,5]-hydride shift to form 1,3,5-hexatriene II. A subsequent bir-electrocyclic ring closure affords intermediate... 

The alkynylation of estrone methyl ether with the lithium, sodium and potassium derivatives of propargyl alcohol, 3-butyn-l-ol, and propargyl aldehyde diethyl acetal in pyridine and dioxane has been studied by Miller. Every combination of alkali metal and alkyne tried, but one, gives the 17a-alkylated products (65a), (65c) and (65d). The exception is alkynylation with the potassium derivative of propargyl aldehyde diethyl acetal in pyridine at room temperature, which produces a mixture of epimeric 17-(3, 3 -diethoxy-T-propynyl) derivatives. The rate of alkynylation of estrone methyl ether depends on the structure of the alkyne and proceeds in the order propar-gylaldehyde diethyl acetal > 3-butyn-l-ol > propargyl alcohol. The reactivity of the alkali metal salts is in the order potassium > sodium > lithium. 

Significantly, silylcuprates react with carbamates with syn stereoselectivity59, similar to their reactions with organocuprates62, whereas other nucleofugal groups, such as acetate or methanesulfonate, are displaced in an anti fashion23,27,57. Thus, both enantiomeric (or epimeric) allenes can be obtained from the same propynyl alcohol precursor. 

Dimetbyl-l, 2-tellurazole1 1.7 g (15 mmol) of hydroxylamine O-sulfonic acid are dissolved in 5 ml of water, the solution is cooled to 0°, and 1.23 g (15 mmol) of methyl propynyl ketone are added to the vigorously stirred solution under nitrogen. The solution is stirred for 35 min and 2.5 g (30 mmol) of sodium acetate and 25 ml (l 5 mmol) of a 0.6 molar aqueous solution of potassium telluride are added to the solution over 20 min. The resultant solution is allowed to warm to 20 and is then stirred for 4 h. The reaction mixture is extracted 4 times with 20 ml portions of ethyl acetate and the extract is dried with anhydrous sodium sulfate, filtered, and evaporated to dryness. The residue is sublimed at 70°/0.001 torr and the sublimate recrystallized from acetone yield 0.3 mmol (10%) m.p. 111 . 

Efficient biochemical processes were developed for the preparation of the two optically active pyrethroid insecticides by a combination of enzyme-catalyzed reactions and chemical transformations. These are based on the findings that a lipase from Arthrobacter species hydrolyzes the acetates of the two important secondary alcohols of synthetic pyrethroids with high enantioselectivity and reaction rate. The two alcohols are 4-hydroxy-3-methy1-2-(2 -propynyl)-2-cyclopentenone (HMPC) and a-cyano-3-phenoxybenzyl alcohol (CPBA). The enzyme gave optically pure (R)-HMPC or (S)-CPBA and the unhydrolyzed esters of their respective antipodes. 

For the production of various pyrethroid insecticides the (S)-4-hydroxy-3-methyl-2-(2-propynyl)-2-cyclopenten-l-one was required. Arthrobacter lipase hydrolysed only the P-enantiomer of the racemic acetate and, after extraction, the mixture of the alcohol and acetate were submitted to methanesulfonyl chloride and triethylamine. The thus-obtained acetate/mesylate mixture was hydrolysed/ inverted yielding 82% of (S)-4-hydroxy-3-methyl-2-(2-propynyl)-2-cyclopenten-l-one with an ee of 90% (Scheme 6.17 B). The procedure was also proved to work with other secondary alcohols and instead of the mesylate a Mitsunobu inversion could be applied [35]. 

C-H bond fission and the production of ethynyl radicals. Butadiyne and vinyl acetate are formed when the T -shaped ethyne dimer is irradiated at 193 nm in argon or xenon. The dynamics of the photodissociation of propyne and allene have been studied. The H2 elimination from propyne is a minor route for propyne dissociation and the major path identified in this study is loss of the alkyne hydrogen. A study of the photodissociation dynamics of allene and propyne has been reported and this work has demonstrated that allene gives rise to a propargyl radical while propyne yields the propynyl radical. Other research has examined the photodissociation of propyne and allene by irradiation at 193 nm. ... 

Geranyl butyrate Vetiveryl acetate Propynyl guaethol... 

A solution containing 100 mg (3.5 mmol) of o-(3-phenoxy-l-propynyl)-a-diazoacetophe-none 2.9b in 300 mL of methylene chloride was irradiated under an Argon atmosphere with a 450 W Hanovia lamp equipped with an Uranium filter sleeve for 20 min. Removal of the solvent under reduced pressure left a dark red oil which was subjected to silica gel chromatography using a 5% ethyl acetate/cyclohexane mixture as the eluant. The major product isolated from the column contained 63 mg (70%) of 7-hydroxy-6ff-benzo[b]-naphtho[l,2-d]pyran 2.9c as a white solid, mp 148 - 149 °C. 

Fig. 14.8. Chemical diagrams a diethylstilbestrol b f-pseudo-diethylstilbestrol, EPD c Z-pseudo-diethylstilbestrol, ZPD d /rows-tamoxifen e medroxyprogesterone acetate f 17a,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione (R5020) g 1 lyS-(4-(dimethyl-amino)phenyl)-l7J8-hy-droxy-17a-(l-propynyl)estra-4,9-dien-3-one (RU38486) h flutamide i l7j8-hydroxy-17a-methyl-4,9,1 l-estratrien-3-one...

To a flame-dried test tube equipped with a magnetic stirring bar was added 2-(2,3-pentadienyl)-2-(3-trimethylsilanyl-2-propynyl)malonic acid diethyl ester (477a, 41 mg, 0.13 mmol) and toluene (0.5 mL). The test tube was evacuated and charged with N2 (this step was repeated 3 times) and [Rh(CO)2Cl]2 (2.5 mg, 6 x 10" mmol) was added. The mixture was stirred at room temperature for 1 h under N2 atmosphere (1 atm). The solvent was removed in vacuo and the residue was purified by flash chromatography (Si02, hexanesrethyl acetate=9 l) to afford 478a as a colorless oil (18.3 mg, 45%). ... 

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