Alkynes heterocyclization

Diazoacetic esters, reactions with alkenes, alkynes, heterocyclic and aromatic compounds, 18, 3 26, 2 a-Diazocarbonyl compounds, insertion and addition reactions, 26, 2 Diazomethane ... 

The Reactions of Diazoacetic Esters with Alkenes, Alkynes, Heterocyclic and Aromatic Compounds V. Dave and E. W. Warnhoff, Org. React., 1970,18, 217-402. Reactions of Singlet Oxygen with Heterocyclic Systems H. H. Wasserman and B. H. Lipshutz, Org. Chem., 1970, 40, 429-509. 

Reviews (a) V. Dave and E. W. Wamhoff, The Reactions of Diazoacetic Esters with Alkenes, Alkynes, Heterocyclic and Aromatic Compounds, in W. G. Dauben, ed., Organic Reactions, Vol. 18, Chap. 3, John Wiley Sons, New York, 1970. (b) G. Maas, Top. Curr. Chem., 137, 75 (1987). (c) J. Salaun, Chem. Rev., 89, 1247 (1989). (d) A. Demonceau, A. J. Hubert, and A. F. Noels, Basic Principles in Carbene Chemistry and Applications to Organic Synthesis, in A. F. Noels, M. Graziani, and A. J. Hubert, eds., Metal Promoted Selectivity in Organic Synthesis, p. 237, Kluwer Academic, Dordrecht, 1991. 

The Reactions of Diazoacetic Esters with Alkenes, Alkynes, Heterocyclic, and Aromatic Compounds Vinod Dave and E. W. Warnhoff... 

Keywords Palladium Catalysis Alkyne Heterocycle Carbocycle... 

Ajami D, Rebek J Jr (2008) Reversible encapsulation of terminal alkenes and alkynes. Heterocycles 76(1) 169-176... 

Two moles of diphenylacetylene insert into the benzyl methyl sulfide complex 481 to afford the eight-membered heterocycle 482[440j. The cinnolinium Salt 483 is prepared by the insertion of alkynes into the azobenzene com-plex[44l]. 

The direct combination of selenium and acetylene provides the most convenient source of selenophene (76JHC1319). Lesser amounts of many other compounds are formed concurrently and include 2- and 3-alkylselenophenes, benzo[6]selenophene and isomeric selenoloselenophenes (76CS(10)159). The commercial availability of thiophene makes comparable reactions of little interest for the obtention of the parent heterocycle in the laboratory. However, the reaction of substituted acetylenes with morpholinyl disulfide is of some synthetic value. The process, which appears to entail the initial formation of thionitroxyl radicals, converts phenylacetylene into a 3 1 mixture of 2,4- and 2,5-diphenylthiophene, methyl propiolate into dimethyl thiophene-2,5-dicarboxylate, and ethyl phenylpropiolate into diethyl 3,4-diphenylthiophene-2,5-dicarboxylate (Scheme 83a) (77TL3413). Dimethyl thiophene-2,4-dicarboxylate is obtained from methyl propiolate by treatment with dimethyl sulfoxide and thionyl chloride (Scheme 83b) (66CB1558). The rhodium carbonyl catalyzed carbonylation of alkynes in alcohols provides 5-alkoxy-2(5//)-furanones (Scheme 83c) (81CL993). The inclusion of ethylene provides 5-ethyl-2(5//)-furanones instead (82NKK242). The nickel acetate catalyzed addition of r-butyl isocyanide to alkynes provides access to 2-aminopyrroles (Scheme 83d) (70S593). 

Furans, thiophenes and pyrroles have all been obtained by addition of alkynic dienophiles to a variety of other five-membered heterocycles, as illustrated in Scheme 104. As the alkynic moiety provides carbons 3 and 4 of the resulting heterocycle, this synthetic approach provides an attractive way of introducing carbonyl containing substituents at these positions, especially as many of the heterocyclic substrates are readily generated. Such reactions do... 

Heterocycles which provide the NOC or CNO component synthon Isoxazoles can be prepared by the thermal or photolytic cleavage of a number of heterocycles, such as 1,3,5-dioxazolidone, furazans, furoxans and 1,3,2,4-dioxathiazole 2-oxides, in the presence of a reactive alkene or alkyne. 

NMR, 3, 542 oxidation, 3, 546 phosphorescence, 3, 543 photoelectron spectra, 3, 542 photolysis, 3, 549 reactions, 3, 543-555 with alkenes, 3, 50 with alkynes, 3, 50 with IH-azepines, 3, 552 with azirines, 3, 554 with cyclobutadiene, 3, 551 with cyclopropenes, 3, 550 with dimethylbicyclopropenyl, 3, 551 with heterocyclic transition metal complexes, 7, 28 29... 

The 1,3-dipolar molecules are isoelectronic with the allyl anion and have four electrons in a n system encompassing the 1,3-dipole. Some typical 1,3-dipolar species are shown in Scheme 11.4. It should be noted that all have one or more resonance structures showing the characteristic 1,3-dipole. The dipolarophiles are typically alkenes or alkynes, but all that is essential is a tc bond. The reactivity of dipolarophiles depends both on the substituents present on the n bond and on the nature of the 1,3-dipole involved in the reaction. Because of the wide range of structures that can serve either as a 1,3-dipole or as a dipolarophile, the 1,3-dipolar cycloaddition is a very useful reaction for the construction of five-membered heterocyclic rings. 

The reaction of tnfluoromethyl-substituted A -acyl umnes toward nucleophiles in many aspects parallels that of the parent polyfluoro ketones Heteronucleophiles and carbon nucleophiles, such as enarmnes [37, 38], enol ethers [38, 39, 40], hydrogen cyanide [34], tnmethylsilylcarbomlnle [2,47], alkynes [42], electron-nch heterocycles [43], 1,3-dicarbonyl compounds [44], organolithium compounds [45, 46, 47, 48], and Gngnard compounds [49,50], readily undergo hydroxyalkylation with hexafluoroace-tone and amidoalkylation with acyl imines denved from hexafluoroacetone... 

Cyclotrithiazyl chloride is also a useful reagent in organic chemistry in the fusion of 1,2,5-thiadiazoles to quinones as well as the synthesis of (a) isothiazoles from 2,5-disubstituted furans and (b) bis-1,2,5-thiadiazoles from A-alkylpyrroles (Scheme 8.4). Alkenes and alkynes react readily with (NSC1)3 to give 1,2,5-thiadiazoles, while 1,4-diphenyl-1,3-butadiene gives a variety of heterocyclic products including a bis(l, 2,5-thiadiazole). ... 

Fluorinated alkenes and alkynes are highly activated toward nucleophilic attack and reaction with bifunctional nucleophiles is a fruitful area for the synthesis of heterocycles. A review on perfluoroalkyl(aryl)acety-lenes contains many examples (91RCR501). 

While these reports are mainly concerned with an evaluation of the peculiar structure of the iminophosphenium cation, this species also reveals cycloaddition properties. The cation shows a [2-t-l] cycloaddition behaviour towards alkynes [50]. With iminophosphanes and alkylazides the cations react with the formation of four- and five-membered heterocyclic ring systems [51], as shown for example in Scheme 9. 

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