Acetylenic carbinols

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Another approach is based on the rearrangement of an acetylenic carbinol formed between ben2aldehyde and acetylene. 

The simplest method for the addition of a 2-carbon fragment to a 17-keto steroid while retaining an oxygen function at C-17 is via reaction with acetylene or a substituted acetylene e.g., ethoxyacetylene, chloroacetylene). Since the resulting acetylenic carbinol (which is usually obtained in excellent yield) can in turn be hydrated, reduced, rearranged, and oxidized, this reaction offers considerable synthetic possibilities. 

S-acetoxy-20-keto-17 a-pregnanes via acetylenic carbinols, 200 Preparation of 20,21-bis-oxygenated pregnanes by side-chain oxygenation of pregnanes... 

The palladium-catalyzed reaction of o-iodoanilides with terminal acetylenic carbinols provides a facile route to the synthesis of quinolines using readily available starting materials (93TL1625). When o-iodoanilide 126 was stirred with acetylenic carbinol 127 in the presence of bis-triphenyl phosphine palladium(ll) chloride in triethylamine at room temperature for 24 h, the substituted alkynol 128 was obtained in 65% yield. On cyclization of 128 with sodium ethoxide in ethanol, 2-substituted quinoline 129 was obtained in excellent yield. 

Hydrogenation of acetylenic carbinols is sometimes accompanied by isomerization to the ketone. In the case of 13, the isomerization to 15 was most pronounced when hydrogenations proceeded very slowly as when impure 13 was used (39). 

The transformations of compounds which are precursors for vitamin A and carotenoids have a special position among the rearrangements of the conjugated polyenes. Numerous isomerizations such as cw-fraws-isomerization, the dehydration of polyunsaturated acetylenic carbinols etc. were utilized to prepare the various carotenoides (e.g. /1-carotene, lycopene, cryptoxanthin, zeaxanthin) (for reviews, see References 146 and 147). However, one of these rearrangements turned out to be a considerable hindrance for the synthesis of target products. 

The reagent 78 was found to be highly effective in the asymmetric reduction of a-acetylenic ketones (89). Acetylenic carbinols were prepared in 75 to 90%... 

Scheme 13) (102). The acetylenic carbinol 94 was obtained in a 93% yield with 84% optical purity. 

The coupling reaction of acetylenic carbinols was also extended to the thiophene series (80). The diacetylenic glycols were of particular interest, since they provide convenient synthetic routes to bifunctional compounds difficult to prepare by other means. The coupling reaction, which took place, could be represented as follows ... 

These studies were extended to the a,/ and y-hydroxy-a,/ -acetylenic acids (61a), (81). We found that the direct carbonation of the sodium salts of thienylacetylenes or of acetylenic carbinols was of no avail even under pressure using various solvents. Small amounts of 2-thenoic acids were isolated only. However, a, -acetylenic acids as well as the... 

This preparation illustrates a general and convenient way of oxidizing secondary alcohols to ketones. The novel feature of the reaction is represented by acetone solvent which affects markedly the properties of the oxidizing agent. The reaction is very rapid (if not instantaneous), and the yields are high, the reagent rarely attacking unsaturated centers. The procedure is applicable to acetylenic carbinols, allyl and other unsaturated alcohols, and saturated carbinols. The main limitation is the low solvent power of acetone. 

Synonyms Ethynol carbinol acetylene carbinol propiolic alcohol 2-propyn-l-ol 2-propynyl alcohol... 

A highly efficient synthesis of l-alkylidene-13-dihydroisobenzofurans and 3-alkylidene isobenzofuran-l(3//)-ones (phthalides) through Pd-Cu-catalysis using acetylenic carbinols as synthons was reported <99SL456>. 

Reduced yields of acetylenic carbinols are often caused by deprotonaiion of the carbonyl compound ... 

In the Favorski reaction [8], etbyne is coupled with a carbonyl compound in the presence of powdered alkali hydroxide suspended in an organic solvent, in which the acetylene has good solubility. Some acetylenic carbinols, derived from ketones, can be obtained in high yields by introducing acetylene at atmospheric pressure. The active intermediate possibly is a metal acetylide formed in low concentration. 

Ethoxyacetylene has proved to be a useful reagent for the conversion of ketones to acetylenic carbinols... 

Acetoxy-20-keto-17a-pregnanes via Acetylenic Carbinols.165 A mixture of 1.9 g of 17a-ethynylestradiol diacetate, 2.1 g of A-bromoacetamide, 2 g of anhydrous sodium acetate, 10 ml of water and 100 ml of acetic acid is left at... 

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