Showing papers on "Ylide published in 1982"
69 citations
TL;DR: The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1. DOI:10.1002/anie.198200010 as mentioned in this paper, 1.
Abstract: The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1. DOI:10.1002/anie.198200010
47 citations
TL;DR: In this paper, the Wittig reaction with aldehydes 2 proceeds with high (Z)-stereoselectivity to give (Z)α,β-unsaturated aldehyde acetals 8 which are cleaved under well defined conditions with p-toluenesulfonic acid or with wet silica gel to (Z-α,α, β-unaturated aldhydes 9.
Abstract: (2-Ethoxyvinyl)triphenylphosphonium-bromid (5) last sich mit Natriumamid in das korrespondierende Phosphaallenylid 6 uberfuhren, das Ethanol zum Ylid 7 addiert. 7 wird auch aus 5 mit Natriumethylat erhalten. Die Wittig-Reaktion von 7 mit Aldehyden 2 verlauft mit hoher (Z)-Stereoselektivitat. Die entstehenden (Z)-α,β-ungesattigten Acetale 8 lassen sich unter Einhaltung definierter Bedingungen mit p-Toluolsulfonsaure oder durch feuchtes Kieselgel zu den (Z)-α,β-ungesattigten Aldehyden 9 spalten.
Cumulated Ylides, XII1). A Stereoselective Synthetic Method for (Z)-α,β-unsaturated Aldehydes
(2-Ethoxyvinyl)triphenylphosphonium bromide (5) is converted with sodium amide into the corresponding phosphaallenylide 6 which adds ethanol forming the ylide 7. 7 is also obtained by the reaction of 5 with sodium ethanolate. The Wittig reaction of 7 with aldehydes 2 proceeds with high (Z)-stereoselectivity to give (Z)-α,β-unsaturated acetals 8 which are cleaved under well defined conditions with p-toluenesulfonic acid or with wet silica gel to (Z)-α,β-unsaturated aldehydes 9.
45 citations
TL;DR: In this article, an efficient synthesis of pyrrolizidine and indolizidines was achieved by reacting tetracyclic hexahydro-1, 3, 5-triazines with olefinic and acetylenic compounds in the presence of trimethylsilylmethyl trifluoromethanesulfonate and cesium fluoride.
Abstract: Efficient synthesis of pyrrolizidines and indolizidines has been achieved by reacting tetracyclic hexahydro-1, 3, 5-triazines with olefinic and acetylenic compounds in the presence of trimethylsilylmethyl trifluoromethanesulfonate and cesium fluoride. This reaction was applied to the synthesis of several pyrrolizidine alkaloids, (±)-trachelanthamidine, (±)-supinidine, and (±)-isoretronecanol.
33 citations
TL;DR: Pyrrolidines were obtained by a new trimethylsilyl triflate-catalyzed cycloaddition of an intermediary N-trimethyl-silylated methyleneiminium ylide, a 1,3-dipole, to olefinic and acetylenic dipolarophiles.
32 citations
TL;DR: In this paper, the reaction of Cp(CO) 2 Mn(η 2 -HCCCO 2 Me) (I) with PPh 3 or (Ph 2 PCH 2 ) 2 gives rise to π-σ-rearrangement of the methylpropiolate ligand in I, yielding the phosphonium ylide complexes Cp[CO] 2 Mn − C(CO 2 Me]CHP + Ph 2 R, where R = Ph or CH 2 CH 2 PPh 2
31 citations
TL;DR: In the presence of AgClO4, chloro(η5-cyclopentadienyl)(triphenylphosphine)palladium(II) was treated with triphenyl-phosphonium benzoylmethylid as discussed by the authors.
28 citations
TL;DR: In this paper, the directing effect of oxygen and sulfur in cycloadditions of nitrile oxides to 2,3-dihydrofuran is evaluated at 2.8 and 1.1 Kcal mol -1 respectively.
25 citations
TL;DR: The reaction of the title compound with methyl iodine gives the ylide 3 and the phosphonium salt 4, and the intermediate formation of the phosphoniaalkene 2 is postulated as mentioned in this paper.
21 citations
Abstract: Alkylation of 2-substituted 3-methyl- or 3-ethylbenzothiazolines with Meerwein reagents gave 2-substituted 3,3-dialkylbenzothiazolinium tetrafluoroborates (3). The configuration of two alkyl groups on the nitrogen was assigned by NMR spectra and NOE measurement. In the Stevens rearrangement of 3 with lithium diisopropylamide ethyl group showed a much larger migratory aptitude (Et:Me≥20 :1) than methyl group irrespective of the configuration of 3, and cyclic ammonium ylide with planar π-type carbanion was proposed as an intermediate. 3 suffered nucleophilic attack at the ring sulfur atom by butyllithium to afford a ring-opened ammonium ylide, which collapses to a radical pair to give unusual Stevens rearrangement product, where o-alkylthiophenyl group migrated selectively in preference to alkyl group, because of stabilization by participation of o-alkylthio group.
20 citations
TL;DR: In this article, a half-benzoylated bibenzyl is converted into its O-dimethylprop-2-ynyl derivative by semi-hydrogenation, Claisen rearrangement, and debenzoylation, followed by hydrogenation and hydrogenolysis of the resulting stilbene.
Abstract: Canniprene (10) is synthesised via reaction of a phenolate-anion ylide with a benzyl-protected aldehyde. Benzoylation, followed by hydrogenation and hydrogenolysis of the resulting stilbene, leads to a half-benzoylated bibenzyl which is converted into its O-dimethylprop-2-ynyl derivative. Semi-hydrogenation, Claisen rearrangement, and debenzoylation gives canniprene. In a second synthesis the prenylated (3-methylbut-2-enylated) and benzyl-protected ring-B section is made first and converted by Wittig reaction into a dibenzyl-protected stilbene. The stilbene is reduced and the benzyl groups removed in one step, without affecting the prenyl group, by sodium in butanol: magnesium in methanol is capable of stilbene reduction without debenzylation. This practical synthesis proceeds in 19% overall yield from the dimethylprop-2-ynyl ether of isovanillin (14) and is applicable to isotope-labelling. The use of p-bromophenacyl (PBP) ether and methoxyethoxymethyl (MEM) ether protection as the basis for canniprene synthesis is also considered.Other bibenzyls relevant to the natural products of Cannabis are made and the methylated chroman (37) derived from canniprene is also synthesised.
TL;DR: In this article, N-Iminoquinolinium ylide reacts with perfluoropropene, perfluorbut-2-ene, and perfluoreopyridine in hot dimethylformamide in the presence of potassium carbonate to yield 2-fluoro-3-(trifluoromethyl)pyrazolo[1,5-a]quinoline, 2,3-bis(triffluoroethyl)-3-biophosphamide, and N-(tetrafluoro-4-pyrid
Abstract: N-Iminopyridinium ylide reacts with perfluoropropene (or 2H-pentafluoropropene) and perfluorobut-2-ene (or perfluorobut-2-yne) to provide 2-fluoro-3-(trifluoromethyl)pyrazolo[1,5-a]pyridine and 2,3-bis(trifluoromethyl)pyrazolo[1,5-a]pyridine, respectively; oxidation of these products with aqueous potassium permanganate gives the corresponding pyrazolecarboxylic acids. Perfluoro-(2-methylpent-2-ene) is attacked by N-iminopyridinium ylide to produce 2-(pentafluoroethyl)-3,3-bis(trifluoromethyl)-3,3a-dihydropyrazolo[1,5-a]pyridine, which can be converted via thermal treatment with tetracyanoethylene into a mixture of 2-(pentafluoroethyl)-3-(trifluoromethyl)pyrazolo[1,5-a]pyridine and 5-(dicyanomethylene)-2-(pentafluoroethyl)-3,3-bis(trifluoromethyl)-3,5-dihydropyrazolo[1,5-a]pyridine. N-Iminoquinolinium ylide reacts with perfluoropropene, perfluorobut-2-ene, and perfluoropyridine in hot dimethylformamide in the presence of potassium carbonate to yield 2-fluoro-3-(trifluoromethyl)pyrazolo[1,5-a]quinoline, 2,3-bis(trifluoromethyl)pyrazolo[1,5-a]quinoline, and N-(tetrafluoro-4-pyridyl)iminoquinolinium ylide, respectively.
TL;DR: Two new types of iso-oxacephems have been synthesized in which a phosphonate group replaces either the carboxyl group or C(3) as mentioned in this paper.
Abstract: Two new types of iso-oxacephems have been synthesized in which a phosphonate group replaces either the carboxyl group or C(3). The latter compound exists as a stable trialkoxyphosphonium ylide.
Potassium thioacetate and O2 in DMF are transformed in an autocatalytic, probably sulfur-catalyzed process to CH3COOK and sulfur; the latter two reagents are sufficient to transform the methanesulfonate 7 to the isopenam 15.
TL;DR: A series of 1,4-bis(4-guanylphenylethyl)benzenes, including masked amidines in which the guanyl function is incorporated into a heterocyclic ring, were prepared for screening as potential antitrypanosomal agents.
TL;DR: In this paper, reaction conditions for the chain extension of 2,3 : 5,6-di-O-isopropylidence-D-mannose (1) with a Wittig ylide (2) to give the acyclic manno-octenoate (3) or the C-glycofuranosides (4 and 5) were described.
Abstract: Reaction conditions are described for the chain extension of 2,3 : 5,6-di-O-isopropylidence-D-mannose (1) with a Wittig ylide (2) to give the acyclic manno-octenoate (3) or the C-glycofuranosides (4 and 5) and with the Knoevenagel–Doebner reaction to afford the isomeric gluco-octenoate (6); the isomerisation proved to occur in the latter reaction provides an explanation for an anomaly in the literature and indicates that the C-glycosides (4 and 5) are formed by a Michael-type ring closure rather than via a betaine intermediate.
TL;DR: In this paper, the Wittig reaction between cyclic anhydrides and methoxycarbonylmethylenetriphenylphosphorane, a reaction used for the preparation of enol-lactones, proceeds via an acyclic intermediate acylated phosphorane.
Abstract: It has been established that the Wittig reaction between cyclic anhydrides and methoxycarbonylmethylenetriphenylphosphorane, a reaction used for the preparation of enol-lactones, proceeds via an acyclic intermediate acylated phosphorane for the three classes of anhydrides studied: succinic, maleic and phthalic. The formation of the acyclic intermediate can be irreversible or reversible, depending on the structure of the anhydride. The stereochemistry of the enol-lactones produced is not controlled by the initial reaction of the anhydride with the ylide but either during or after cyclization of the acyclic intermediate. Product formation appears to be under kinetic control with all the anhydrides studied. The influence of substituents in substituted phthalic anhydrides has been investigated.
TL;DR: In this article, the application of the Michaelis-Becker variation to the preparation of unsymmetrical F -methylene bis-phosphonates gives a mixture of both symmetrical and non-symmetric bis -phosphonsates.
TL;DR: In this article, it was shown that pyrolysis of the stable 6H-dibenzo[b,d]thiopyran-5-io(bismethoxycar-bonyl)methanide (7e) gave only the product of insertion of bistethoxycarbonylcarbene into the C(6)−H bond, i.e. the malonate (4e), whereas almost exclusive formation of the ringexpansion product (3f) occurred on pyrolysizing of the 6
Abstract: Reaction of 6-phenyl-6H-dibenzo [b,d]thiopyran (1b) with diphenyldiazomethane (2a) in refluxing benzene affords 6,6,7-triphenyl-6,7-dihydrodibenzo[b,d]thiepin (3b) as major product, together with minor amounts of 6-diphenylmethyl-6-phenyl-6H-dibenzo[b,d]thiopyran (4b). Analogous results are obtained from the reaction of 6H-dibenzo[b,d]thiopyran (1a); however, in this case the yields of the corresponding ring-expansion and insertion products (3a) and (4a) are similar. Copper(II) sulphate-catalysed thermal decomposition of ethyl diazoacetate (2b) in the presence of (1b) yields mainly ethyl 6-phenyl-6H-dibenzo[b,d]thiopyran-6-ylacetate (4d), together with minor amounts of (probably) 6-ethoxycarbonyl-7-phenyl-6,7-dihydrodibenzo[b,d]thiepin (3d), but only the product of insertion of ethoxycarbonylcarbene into the C(6)–H bond, i.e. (4c), is observed from the reaction of (2b) with (1a). Formation of the products (3) and (4) is rationalized in terms of a thermal ylide exchange reaction of the unstable sulphonium ylides (7a–d), initially produced in competition with a Stevens-type rearrangement.In support of the above mechanism, pyrolysis of the stable 6H-dibenzo[b,d]thiopyran-5-io(bismethoxycar-bonyl)methanide (7e) gave only the product of insertion of bismethoxycarbonylcarbene into the C(6)–H bond, i.e. the malonate (4e), whereas almost exclusive formation of the ring-expansion product (3f) occurred on pyrolysis of the 6-phenyl derivative of the ylide (7e).
TL;DR: In this article, a mixture of s -triazolo[1,5-a ]pyridine (IV) and a compound thought to be its dihydro-analogue (V) were isolated following attack on perfluoroacetonitrile by the parent ylide (I); the former product was also prepared by heating 1,2-diamino-pyridinium iodide with trifluoro acetic anhydride.
TL;DR: On 1n, π* -excitation 5, 6-epoxy-2-hydroxy-5, 6dihydro-β-ionone ((E)-4) shows the typical behaviour of a, β-unsaturated γ, δ-EPoxy ketones undergoing primarily C(γ), O-cleavage of the oxiran as mentioned in this paper.
Abstract: On 1n, π* -excitation 5, 6-epoxy-2-hydroxy-5, 6-dihydro-β-ionone ((E)-4) shows the typical behaviour of a, β-unsaturated γ, δ-epoxy ketones undergoing primarily C(γ), O-cleavage of the oxiran. However, 1π, π*-excitation of (E)−4 leads to enol ether 10 which is formed by intramolecular insertion of the hydroxyl group of the ylide c.
TL;DR: The intramolekulare Wittig reaction of the ylide 8b leads to the dihydronaphthacene 9b which can be transformed into the ketol 16 by cis-hydroxylation and pyridinium chlorochromate oxidation as discussed by the authors.
TL;DR: In this article, the ylide complex was determined by X-ray crystallography and a novel migration of Cl from a CH 2 group to Pt. The structure of the Ylide Complex has been determined.
TL;DR: In this article, the coordination properties of phosphorus ylides towards electropositive metals are greatly improved in systems, where the carbanionic charge can be delocalized into the aromatic rings of substituents, as illustrated in the title compounds.
Abstract: Abstract Coordination properties of phosphorus ylides towards electropositive metals are greatly improved in systems, where the carbanionic charge can be delocalized into the aromatic rings of substituents, as illustrated in the title compounds. The ferrocenyl-substituted ylide 2, synthesized from bis(diphenylphosphino)methane and (ferrocenyl)trimethyl-ammonium iodide via the phosphonium salt intermediate 1, is thus easily converted into the alkali complexes 3 a, b on treatment with NaNH2 or KH in tetrahydrofuran, respectively. The intensely coloured products are soluble in a number of organic solvents. NMR spectra of these solutions provide evidence for an interaction between alkali cations and the ferrocenyl rings. - From (C6H5)2CH2P(C6H5)2 and ferrocenylmethyl chloride a di-quaternary salt 4 is obtained, which yields a double-ylide mixture 5 a, b on treatment with base. Hydrolysis of this product affords the ylidic phosphine oxide 6. - The reaction of the ylides 7 and 9 (described previously) with NaNH2, KH or barium metal (in liquid ammonia) leads to the (earth) alkali complexes 8a-c and 10a, b, respectively. With the exception of 8c, but similar to 3a, these materials contain tetrahydrofuran solvate molecules. The 23Na NMR spectrum of 8a and the pronounced quadrupole broadening of the P(III) signals by the alkali cations in the 31P NMR spectra of 8 a, b allow structural suggestions for the solution state as proposed in the formulae. Further treatment of 10b with KH yields a potassium complex 11, characterized, i.a., via a corresponding diquaternary salt 12.
TL;DR: In this paper, a tetravalent sulfur compound, 1,3,6-triphenylimidazo[ 1,2-c]thialvzole, was synthesized, which reacted with N-(p-tolyl)maleimide as both an azomethine ylide and a thiocarbonyl y lide 1, 3-dipole yielding four 1:1 adducts that contained each endo and exo isomers.
Abstract: A novel tetravalent sulfur compound, 1,3,6-triphenylimidazo[ 1,2-c]thialvzole, was synthesized, which reacted with N-(p-tolyl)maleimide as both an azomethine ylide and a thiocarbonyl ylide 1,3-dipole yielding four 1:1 adducts that contained each endo and exo isomers. The cycloadducts of azomethine ylide were found to isomerize into those of thiocarbonyl ylide through a retro 1,3-dipolar cycloaddition reaction. It was offered that this nitrogen-bridged tetravalent sulfur compound was to be designated as a bi-perifunctional compound.
TL;DR: In this article, the principal product of gas phase thermal decomposition of 2-methoxy-2,5,5-trimethyl-Δ3-1,3,4-oxadiazoline (mETHoxyoxa-diazoline) was found to be 1-methylethenyloxy]-ethane (vinyl ether).
Abstract: The principal product of gas phase thermal decomposition of 2-methoxy-2,5,5-trimethyl-Δ3-1,3,4-oxadiazoline (methoxyoxa-diazoline) was found to be 1-methoxy-1-[(1-methylethenyl)oxy]-ethane (vinyl ether). This arises from a selective 1,4-hydrogen shift in the carbonyl ylide intermediate. Fragmentation of the carbonyl ylide is the dominant process in the solution thermolysis of methoxyoxadiazoline. The phase and temperature dependence of this thermolysis is discussed in terms of the probable structure of the carbonyl ylide intermediate.
TL;DR: In this article, the Wittig reaction was used for the synthesis of stilbene, 1,4-diphenylbutadiene, and vitamin A acetate.
Abstract: Dicyano(fluoren-9-ylidene)methane (1a), dicyano(2,7-dibromofluoren-9-ylidene)methane (1b), and ethyl 2-cyano-2-fluoren-9-ylideneacetate (1c) may be cathodically reduced in N,N-dimethylformamide to give dianions which efficiently convert phosphonium salts into ylides. The potentials required are sufficiently modest to allow the electrogeneration of the bases in the presence of several phosphonium salts and of several aldehydes to give a convenient method of carrying out the Wittig alkene synthesis. This method has been explored for the synthesis of stilbene, 1,4-diphenylbutadiene, and vitamin A acetate. The basicity of the dianions varies according to the choice of electrolyte cation (Bu4N+ or Li+). The cations also have a marked effect on the stereochemical course of the reaction and, in particular, mixtures of alkenes are obtained in which the cis-isomer predominates in the presence of lithium ion; in the vitamin A acetate synthesis, the 11 -cis-isomer constitutes 76% of the product. The results are consistent with recent hypotheses concerning the mechanism of the Wittig reaction.
TL;DR: In this paper, the sulfinyl carbanions have been observed to have low reactivity towards neutral transition metal organometallic systems and when reactions do occur they usually involve salt eliminations and formation of complex mixtures containing inter alia organic sulfides, disulfides, freed ligands or their oxides and reduced forms of the organometal reactants.
TL;DR: In this article, a stable, easily prepared reagent which requires only a thermolysis to serve as a convenient in situ source of phosphorus ylide was disclosed, allowing routine olefinations to be achieved with minimal experimental difficulty.