Allgemeine und einfache Synthese von Aryl- und Heteroarylacetylenen

Abstract

das leicht aus der Ligandenebene geriickte Metallion und der tetraedrische Methylenkohlenstoff der Ligandenbrucke wurden hierzu beriicksichtigt und unter Annahme einer helicalen Struktur angeordnet. Daraus resultiert ein Hohiraum im Innern des polymeren Molekiils (Durchmesser z 7 A), womit das selektive Adsorptionsvermogen in Einklang ist. So wird Tetrachlormethan rnit einem Durchmesser von 6.88 A noch gut aufgenommen, yahrend 1,3,5-Triethylbenzol rnit einem Durchmesser von 9 A nicht adsorbiert wird.Abb. 2. Hohlraum in einer moglichen Helix-Struktur der Verbindung ( I ) (schematisch).

Ethynylindoles and their derivatives. Methods of synthesis and chemical transformations (review)

“…The transformation of the isoxazolone 23 into the indole 8 probably takes place through the formation of the intermediate carbene 24. This method also proved quite useful for the synthesis of other hetarylacetylenes difficult to obtain by traditional methods [17]. The analogous thermal decomposition of 5-(3-indolylmethylene)-and 5-(2-indolylmethylene)-2,2-dimethyl-1,3-dioxane-4,6-diones 28a-b and 29, formed with high yields by the Knoevenagel reaction of 2(3)-formylindoles 21, 25, and 26 with 2,2-dimethyl-1,3-dioxane-4,6-dione 27 (Meldrum's acid) in benzene at ~20°C for 24 h, gave a series of ethynylindoles 8, 32, and 35 with position 1 of the ring free and substituted.…”

“…MeCOCH 2 OSiMe 2 Bu-t 3-Ethynylindole 8 was synthesized with a high yield by the thermal decomposition of 3-methyl-4-(3-indolylmethylene)-5(4H)-isoxazolone (23) at 700-800°C and pressure 10 −3 -10 −4 mm Hg [17]. The required isoxazolone 23 was obtained with a yield of 90% by the condensation of 3-formylindole (21) with 3-methyl-5(4H)-isoxazolone (22).…”

Falling‐Solid Flash Vacuum Pyrolysis: An Efficient Preparation of Arylacetylenes

“…[2] Thes ynthesis of the p-nitrobenzylidene isoxazolone 9 took an unexpected course.Infact, the product of reaction of 3-methylisoxazolone (4)w ith p-nitrobenzaldehyde was the bis(isoxazolyl)methane derivative 8,which is far too involatile for conventional FVP.However,falling-solid pyrolysis of 8 at 750 8 8Ca fforded 10 in 71 %y ield (Scheme 2). [2] Thes ynthesis of the p-nitrobenzylidene isoxazolone 9 took an unexpected course.Infact, the product of reaction of 3-methylisoxazolone (4)w ith p-nitrobenzaldehyde was the bis(isoxazolyl)methane derivative 8,which is far too involatile for conventional FVP.However,falling-solid pyrolysis of 8 at 750 8 8Ca fforded 10 in 71 %y ield (Scheme 2).…”

“…[2] Thegreat advantage of the FS-FVP method is that multigram quantities can be obtained in af ew hours. [2] Thegreat advantage of the FS-FVP method is that multigram quantities can be obtained in af ew hours.…”

“…The popularity of click chemistry [1] has sparked renewed interest in the synthesis of acetylenes.Flash vacuum pyrolysis (FVP) of 4-methyleneisoxazol-5(4H)-ones 1,r eadily synthesized from 3-methylisoxazolone and aldehydes,gives access to av ariety of alkynes 3 in high yields (Scheme 1). [2] Details of the mechanism of the reaction have been investigated computationally, [3] and it has been found to take place via transient ethynylidenes 2,w hich by 1,2-hydrogen migration afford the acetylenes 3.T his reaction and its reverse,t he acetylene-vinylidene rearrangement, are of considerable theoretical interest. [4] Analogous FVP of 4-aminomethyleneisoxazolones allowed the generation and characterization of ethynylamines RR'NÀCCÀHa nd RNHÀCCÀHa nd ketenimines RÀN=C=CH 2 .…”