NMR study,theoretical calculations for assignment of the Z‐ and E‐isomers,and kinetics investigation of stable phosphorus ylides involving a 2‐mercapto‐4,6‐dimethyl pyrimidine

In the present work, NMR, theoretical, kinetics, and mechanism investigations were undertaken for a one‐pot condensation reaction between 2‐mercapto‐4,6‐dimethyl pyrimidine and dialkyl acetylenedicarboxylates in the presence of triphenyphosphine containing novel stable phosphorus ylides 4a–c . Herein, theoretical calculations have been employed for assignment of the most stable isomers (Z or E) of phosphorus ylides 4a,c by natural population analysis, atoms in molecules methods, and CHelpG keyword, in which E‐ 4(a, c) are more stable forms as the majors. The ¹H, ¹³C, and ³¹P NMR data of these ylides are consistent with results obtained from theoretical calculations. In addition, kinetic investigation of new ylides was undertaken by ultraviolet spectrophotometry. Useful information was obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates), and also the concentration of reactants on the rate of reactions. The proposed mechanism was confirmed according to the obtained results and a steady‐state approximation, and the first step (k₂) of the reaction was recognized as a rate‐determining step on the basis of the experimental data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:462–474, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20632     

Scope and limitations of cyclopropanations with sulfur ylides

The rates of the reactions of the stabilized and semistabilized sulfur ylides 1a-g with benzhydrylium ions (2a-e) and Michael acceptors (2f-v) have been determined by UV-vis spectroscopy in DMSO at 20 °C. The second-order rate constants (log k(2)) of these reactions correlate linearly with the electrophilicity parameters E of the electrophiles 2 as required by the correlation log k(2) = s(N + E), which allowed us to calculate the nucleophile-specific parameters N and s for the sulfur ylides 1a-g. The rate constants for the cyclopropanation reactions of sulfur ylides with Michael acceptors lie on the same correlation line as the rate constants for the reactions of sulfur ylides with carbocations. This observation is in line with a stepwise mechanism for the cyclopropanation reactions in which the first step, nucleophilic attack of the sulfur ylides at the Michael acceptors, is rate determining. As the few known pK(aH) values for sulfur ylides correlate poorly with their nucleophilic reactivities, the data reported in this work provide the first quantitative approach to sulfur ylide reactivity.     

Synthesis and dynamic 1H NMR study around the carbon–carbon double bond in the new stable phosphorus ylides derived from the reaction between hexamethyl phosphorous triamide and dimethyl acetylenedicarboxylate in the presence of NH‐heterocyclic compounds

New and stable phosphorous ylides are obtained from a simple and efficient one‐pot three‐component reaction between hexamethyl phosphorous triamide and dimethyl acetylenedicarboxylate in the presence of NH‐heterocyclic compounds in excellent yields at an ambient temperature. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group. Dynamic effects are observed in the ¹H NMR spectra that are attributed to the restricted rotation around the carbon–carbon double bond. The experimental rotational energy barrier (Δ G^#) and other activation parameters on the basis of the ¹H NMR study for the rotational interchangeable process of major and minor isomers in ylides 4a–d are reported. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:131–137, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20761     

A Facile,One-Pot Synthesis of Azoic Compounds and Anthraquinone Derivatives Containing Dialkyl Phosphoryl Moieties in Multicomponent Reactions

Protonation of the reactive 1:1 intermediates produced in the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates by 1-amino-anthraquinone or 1,5-diphenylcarbazone as a core dye leads to vinyl phosphonium salts, which undergo Michael addition with conjugate base of NH compounds to produce stable phosphorus ylides as novel dyes in fairly good yields. These ylides can exist in two geometrical isomers (Z) and (E) for 3, because the negative charge of the ylide moiety of these compounds are strongly conjugated with the adjacent carbonyl group. Rotation around the carbon–carbon double bond is slow in the (Z) and (E) geometrical isomers on the NMR time scale at ambient temperature. These compounds are assigned by their IR, ¹H, ¹³C NMR spectral data as well as their mass spectroscopic data.     

Synthesis of New Stable Phosphorus Ylides and 1,4‐Diionic Organophosphorus Compound from a Reaction between Hexamethyl Phosphorous Triamide and Dimethyl Acetylenedicarboxylate in the Presence of CH‐Acids

A simple and efficient one‐pot three‐component reaction between hexamethyl phosphorous triamide and dimethyl acetylenedicarboxylate (DMAD) in the presence of CH‐acids, such as acetylacetone, 1,3‐indandione, dibenzoylmethane, anthrone, and N,N‐dimethylbarbituric acid, has been studied. In all cases, new and stable phosphorus ylides are obtained in excellent yields. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond, resulting from conjugation of the ylide moiety with the adjacent carbonyl group. From the reaction of N,N‐dimethylbarbituric acid with DMAD in the presence of hexamethyl phosphorous triamide, a 1,4‐diionic organophosphorus compound is obtained. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:84–89, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21067     

Immonium ylides derived from halocarbenes in the synthesis of nitrogen-containing compounds

Reactions of halocarbenes with imines, ketenimines, and aromatic azaheterocycles, which proceed through the corresponding azomethine ylides, keteneimine ylides, and cycloimmonium ylides, are reviewed. New routes for the synthesis of halo- and nitrogencontaining compounds using the transformations of halosubstituted immonium ylides are discussed.The paper is based on an invited lecture at the fifth Conference on Carbene Chemistry (Moscow, September 16–18, 1992).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 646–654, April, 1993.     

Tetraphenylcyclopentadienylides

The properties of a number of heteronium tetraphenylcyclopentadienylides with a variety of hetero-atoms are reported, including their UV spectra, basicities, and reactivities towards aldehydes and nitrosobenzene. These properties are very dependent on the identity of the hetero-atoms; with elements of either Group V or Group VI of the periodic table the dipolar and nucleophilic character of the ylides increases and their stability decreases as one descends the periodic table.     

An Efficient One-Pot Synthesis of 2,3-Dialkyl-1,1-Diethyl-1-(Acetylamino)-3-(1,1,1-Triphenylphosphanilidene)-1,1,2,3-Propanetetracarboxylates and Their Temperature-Dependent NMR Spectra

Abstract

Stable crystalline phosphorus ylides of 1,1-diethyl 2,3-dimethyl 1-(acetylamino)-3-(1,1,1-triphenylphosphanilidine)-1,1,2,3-propanetetracarboxylates were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of diethyl acetamidomalonate as a CH-acid. These stable ylides exist in solution as a mixture of two geometrical isomers (E and Z) as a result of restricted rotation around the carbon–carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group on the nuclear magnetic resonance (NMR) time scale at ambient temperature. The dynamic effects in the ylide moieties were investigated by ¹H NMR spectra.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Study of the reaction of 4-chloromethylene-2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylcyclohexa-2,5-dien-1-one with the P(III) acids esters

The main stable products of the reactions 4-chloromethylene-2,6-di-tert-butylcyclohexa-2,5-dien-1-one with triethyl phosphite and ethyl diphenylphosphinite are the phosphorylated phosphorus ylides, 3,3′,5,5′-tetra-tert-butylstilbenequinone, and biphosphorylated sterically hindered phenols.     

Regioselektive 1,3-dipolare Cycloadditionen von Thiocarbonyl-yliden mit 1,3-Thiazol-5(4H)-thionen

Regioselective 1,3-Dipolar Cycloadditions of Thiocarbonyl Ylides with 1,3-Thiazole-5(4H)-thiones The thiocarbonyl ylides 13 and 1,3-thiazol-5(4H)-thiones 1 undergo a smooth reaction to yield spirocyclic 1,3-dithiolanes 14 – 16 (Schemes 4–6). The 1,3-dipolar cycloadditions occur in a regioselective manner, but the orientation of the thiobcnzophenone-S-methylide ( 13b ) differs from that of the cycloalkane thione-S-methylides 13a and 13c . Whereas the 1,3-cycloadduct with 13b is formed in accordance with frontier-orbital considerations, the inverse orientation in the reactions with 13a and 13c most likely is the result of steric hindrance in the transition state. The thiocarbonyl ylides have been prepared in situ from the corresponding 2,5-dihydro-1,3,4-thiadiazoles 12 . The more stable aliphatic precursors 12a and 12c undergo decomposition at 50°, the unstable 12b at ?30°.     

Phosphorus-ylides: powerful substituents for the stabilization of reactive main group compounds

Phosphorus ylides are 1,2-dipolar compounds with a negative charge on the carbon atom. This charge is stabilized by the neighbouring onium moiety, but can also be shifted towards other substituents thus making ylides strong π donor ligands and hence ideal substituents to stabilize reactive compounds such as cations and low-valent main group species. Furthermore, the donor strength and the steric properties can easily be tuned to meet different requirements for stabilizing reactive compounds and for tailoring the properties and reactivities of the main group element. Although the use of ylide substituents in main group chemistry is still in its infancy, the first examples of isolated compounds impressively demonstrate the potential of these ligands. This review summarizes the most important discoveries also in comparison to other substituents, thus outlining avenues for future research directions.

The application of ylide substituents as strong donor ligands for the stabilization of reactive main group compounds with unusual properties and reactivities is discussed.     

Cascade reactions of nitrogen-and phosphorus-containing ylides with methyl diazoacetate and in situ generated diazocyclopropane

Reactions of pyridinium or phosphorus ylides with diazo esters are multistep processes. The first step is covalent bonding between the ylide C atom and the terminal N atom. This is followed by elimination of the ylide-forming molecule and successive addition of one or two ylide fragments. Depending on the nature of the starting reagents, this type of transformations leads to novel polyfunctional phosphorus ylides or, with pyridinium ylides, to polyalkyl 3,4(4,5)-diazaalkadienetri-or tetracarboxylates. A reaction of the in situ generated diazocyclopropane with methyl triphenylphosphoranylideneacetate stops at the first step, giving a cyclopropylazo-containing ylide. Reactions of the latter with acyl chlorides yield six-membered heterocyclic betaines with a triphenylphosphonium substituent. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 108–113, January, 2006.     

Utilisation d'ylides du phosphore en chimie des sucres. XV. Synthèse de sucres à insaturation terminale

Treatment of 3-O-benzyl-1, 2-O-isopropylidene-3-O-methyl-α-D -xylo-pentodialdlo-1,4-furanose and 2,5-anhydro-3,4-O-isopropylidene-aldehydo-D -ribose with moderately stable and stable phosphonium ylides led to the corresponding terminal-unsaturated sugars obtained as a mixture of cis and trans isomers. The cis:trans ratios were determined by ¹H-NMR. and (or) GLC. They showed that steric factors play an important role in the control of the stereochemistry of these reactions.     

Silica-Gel–Catalyzed Conversion of Stabilized Phosphorus Ylides to Benzo[e][1,3]Thiazocin Derivatives

The reaction between triphenylphosphine, dialkylacetylenedicarboxylates, and N-benzoyl thiourea derivatives leads to intermediates such as vinyltriphenylphosphonium salts, which undergo Michael addition to produce the highly functionalized phosphorus ylides containing alkyl groups in excellent yields. Using silica gel as a catalyst, the conversion of the stabilized phosphorus ylides to benzo[e][1,3]thiazocin derivatives in solvent free conditions at 90°C in fairly high yields is achieved.     

Reversible C ⇆ N migration of the ethoxycarbonyl group in the reactions of pyridinium and isoquinolinium ylides derived from malonic ester with isocyanates

Pyridinium and isoquinolinium ylides ( 7 and 12 ) derived from malonic ester react in an unusual manner with isocyanates giving the new pyridinium ylide ( 9 ) and the new isoquinolinium ylide ( 14 ). C → N Migration of the COOEt group takes place at room temperature, but, at an elevated temperature, reverse N → C migration of the COOEt group proceeds and ylides 9 and 14 are reconverted into the starting ylides 7 and 12 , respectively. © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:36–45, 2002; DOI 10.1002/hc.1104     

Electrocyclic Ring Opening Reactions of Ethylene Oxides

Substituents capable of stabilizing negative charge endow ethylene oxides with the ability to undergo electrocyclic ring opening at the CC bond; heating or irradiation generates small equilibrium concentrations of carbonyl ylides which can engage in 1,3-dipolar cycloadditions. Apart from the normal conrotatory mode of ring opening, predicted by the Woodward-Hoffmann rules, the disrotatory process, forbidden by orbital symmetry, also appears to occur in the case of α-cyano-cis-stilbene oxide. Kinetic studies on α-cyano-trans -and -cis-stilbene oxide permit construction of the energy profile for electrocyclic ring opening to give the stereoisomeric carbonyl ylides and for their recyclization and rotation.     

Studies on the Aromatic Dihalocarbonyl Ylides and Their Deoxygenation

The deoxygenation reaction of heptanones, cycloheptanone, cycloheptatrienone or substituted cycloheptatrienone with dihalo-carbene results in carbon monoxide and corresponding halides. The yield of CO produced by 2 , 4 , 6-triphenylcycloheptatrienone is 2.6-3.5 times as high as that produced by the saturated heptanones. The structures, energies, charge distributions, bond orders, and other relative parameters of the dihalocarbonyl glides were calculated by using the SCF-MNDO method. The obtained data reveal that the ylides from cycloheptatrienone have aromatic structure and are different from those produced from saturated cycloheptanone. The reactivities of the dihalocarbonyl ylides are discussed. It is proposed that this aromatic structure should be responsible for the high yield of CO from the reaction of cycloheptatrienone with dihalocarbene.     

Transition-Metal Free Catalytic Synthesis of Trifluoromethyl Indolines by [4+1] Cycloaddition of Trifluoromethyl Benzoxazinones with Sulfur Ylides

Stereoselective catalytic synthesis of 3-trifluoromethyl indolines through the [4+1] cycloaddition of benzoxazinones and sulfur ylides in a transition-metal-free manner was developed. In the presence of a catalytic amount of sodium hydride, aza-ortho-quinone methide intermediates were formed from trifluoromethyl benzoxazinones through decarboxylation after the first nucleophilic attack of sulfur ylides, which progressed to a second nucleophilic attack of sulfur ylides, resulting in the [4+1] cycloaddition. The key for this catalytic transformation is the dual attack of sulfur ylides on substrates. This unique transition-metal-free protocol is applicable to the synthesis of non-fluorinated vinyl-, ethynyl- or methyl-substituted indolines. The synthesis of 3-trifluoromethyl indoles was also achieved described under stoichiometric conditions.     

New Tandem Reactions of Metal Carbenoids. Intermolecular Formation of Azomethine Ylide from Methyl 2-Diazo-2-phenylacetate and Schiff Base: Intramolecular 1,3-Dipolar Cycloaddition

Rhodium acetate-catalyzed decomposition of methyl 2-diazo-2-phenylacetate in the presence of substituted N-methylbenzylideneamines possessing an activated alkenyl fragment (dipolarophile) in the side chain gives products of intramolecular cycloaddition of intermediate Z,E- and E,Z-azomethine ylides. The cycloaddition is regioselective, and the products are hexahydrochromeno[4,3-b]pyrrole derivatives. The stereoselectivity of the process depends on the temperature. In the temperature range from 20 to 80°C, the major stereoisomer is that with cis junction of the tetrahydropyran and pyrrolidine rings. N-Phenylazomethine ylides generated from methyl 2-diazo-2-phenylacetate and alkyl 4-[2-(phenyliminomethyl)phenoxy]-2-butenoates at 40°C undergo cyclization to aziridines at a higher rate, as compared to the rate of cycloaddition to the internal dipolarophile. N-Phenylazomethine ylides generated by thermolysis of the corresponding aziridine or by the “deprotonation” method react with equal regio- and stereoselectivity to give intramolecular cycloaddition products, hexahydrochromeno[4,3-b]pyrrole derivatives with trans-fused tetrahydropyran and pyrrolidine rings. Analysis of the experimental and calculation data suggests preference of the endo transition state in the cycloaddition of the examined azomethine ylides.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 939–949.Original Russian Text Copyright © 2005 by Khlebnikov, Novikov, Bespokoev, Kostikov, Kopf, Starikova, Antipin.     

Preparation and Some Reactions of 1H-1,4-Benzothiazine Ylides (= 1H-1,4-Benzothioniaazin-4-ide)

A series of fifteen 1H-1,4-benzothiazine ylides were obtained by alkylation of the corresponding 4H-1,4-benzothiazines 1 . Ylides of type 2g–r showed slight [1,2] rearrangements upon thermolysis besides main dealkylation to 1 and olefin production. The ylides of this type underwent redox reactions when treated with hydrazine hydrate alone, giving 3,4-dihydro-2H-1,4-benzothiazines mainly, while ylides of type 2a–f failed to react.