Equivalent Of Dimethyl Acetylenedicarboxylate Research Articles

Reactions of 3а,6a-diaza-1,4-diphosphapentalene with activated acetylenes

The reaction of cyclohexane-annulated 3 a,6a-diaza-1,4-diphosphapentalene (DDP) with di-tert-butyl acetylenedicarboxylate (DBAD) affords the 1,3-dipolar cycloaddition product of the acetylene moiety to the phosphorus and sp2-carbon atoms of DDP in 90% yield. No individual products were isolated in the reaction of DDP with dimethyl acetylenedicarboxylate (DMAD). In the three-component DDP–DMAD–carbazole system (1: 2: 1), a product was generated in 73% yield via successive reactions, including the 1(P),3(C)-dipolar cycloaddition of DMAD to DDP, the addition of the second equivalent of DMAD to the three-coordinate phosphorus atom of the intermediate, and the NH addition of carbazole at the unsaturated C=C bond of the second DMAD moiety. The structures of the reaction products were established by X-ray diffraction.

Heterometallic complexes with cube-type [MTi3N4] cores containing Group 10 metals in a variety of oxidation states.

Treatment of [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] (1) with one equivalent of [Ni(cod)2] (cod = 1,5-cyclooctadiene) in toluene at 60–80 °C and subsequent addition of diphenylacetylene, trans-stilbene or triphenylphosphane afforded the nickel(0) complexes [LNi{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (L = PhCCPh (2), PhCH≡CHPh (3), PPh3 (4)). The nickel(II) complex [I2Ni{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (5) was prepared by analogous addition of iodine to the solution obtained from the heating of 1 and [Ni(cod)2]. Treatment of 1 with one equivalent of [Pd(dba)2] (dba = dibenzylideneacetone) in toluene at room temperature led to the palladium(0) complex [(dba)Pd{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (6). Compound 6 reacted immediately with chloroform-d1 to give the palladium dichloride derivative [Cl2Pd{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (7), which was prepared by treatment of 1 with [PdCl2(cod)] at room temperature. Addition of iodine to a toluene solution of 6 afforded the analogous palladium(II) derivative [I2Pd{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (8). Complex 6 reacted with two equivalents of dimethylacetylenedicarboxylate (dmad) to give the metallacyclopentadiene palladium(II) complex [{(MeOOC)4C4}Pd{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (9) via oxidative coupling. The treatment of 1 with [Pt(nbe)3] (nbe = norbornene) in toluene at room temperature gave the platinum(0) complex [(nbe)Pt{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (10). Compound 10 reacted with excess iodine to afford the platinum(IV) ionic derivative [I3Pt{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}]2(I3)(I5) (11) via an intermediate platinum(II) complex [I2Pt{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (12). The X-ray crystal structures of 5, 8, 9 and 11 have been determined.

Transition Metal Complexes of Bulky, Electron-Rich N-Phosphanyl-Substituted N-Heterocyclic Carbenes (NHCP Ligands). Small Bite Angle Four-Membered (κ-C,κ-P) Chelate Structures

Bulky, electron-rich N-phosphanyl-substituted N-heterocyclic carbenes (NHCP ligands: EtCNP 3, MesCNP 5a, DippCNP 5b) are potential ligands for strained, very small bite angle four-membered transition metal chelate complexes with (κ-C,κ-P) metal coordination. Various compounds of this type have been synthesized and were fully characterized inter alia by X-ray crystallography. Reactions of isolated NHCP species 3, 5a, and 5b with appropriate metal precursors furnished a series of (κ-C,κ-P)-coordinated four-membered NHCP chelate complexes for the metals of the nickel triad and for ruthenium. The cis-dimethyl Pd(II) complex (MesCNP-κC,κ-P)PdMe2 (8) reacted at room temperature with acceptor-substituted alkenes such as fumaronitrile and maleic anhydride to yield the corresponding η2-olefin complexes 9 and 10 with reductive elimination of ethane. Palladacyclopentadiene complex 11 was formed by addition of two equivalents of dimethyl acetylene dicarboxylate to complex 8 via alkyne–alkyne coupling.

Investigations on the Coupling of Ethylene and Alkynes in [IrTp] Compounds: Water as an Effective Trapping Agent

The reaction of the bis(ethylene) complex [Tp(Me(2) )Ir(C(2)H(4))(2)] (1) (Tp(Me(2) ): hydrotris(3,5-dimethylpyrazolyl)borate) with two equivalents of dimethyl acetylenedicarboxylate (DMAD) in CH(2)Cl(2) at 25 degrees C gives the hydride-alkenyl species [Tp(Me(2) )IrH{C(R)=C(R)C(R)=C(R)CH=CH(2)}] (2, R: CO(2)Me) in high yield. A careful study of this system has established the active role of a number of intermediates en route to producing 2. The first of these is the iridium(I) complex [Tp(Me(2) )Ir(C(2)H(4))(DMAD)] (4) formed by substitution of one of the ethylene ligands in 1 by a molecule of DMAD. Complex 4 reacts further with another equivalent of the alkyne to give the unsaturated metallacyclopentadiene [Tp(Me(2) )Ir{C(R)=C(R)C(R)=C(R)}], which can be trapped by added water to give adduct 7, or can react with the C(2)H(4) present in solution generating complex 2. This last step has been shown to proceed by insertion of ethylene into one of the Ir--C bonds of the metallacyclopentadiene and subsequent beta-H elimination. Complex 1 reacts sequentially with one equivalent of DMAD and one equivalent of methyl propiolate (MP) in the presence of water, with regioselective formation of the nonsymmetric iridacyclopentadiene [Tp(Me(2) )Ir{C(R)=C(R)C(H)=C(R)}(H(2)O)] (9). Complex 9 reacts with ethylene giving a hydride-alkenyl complex 10, related to 2, in which the C(2)H(4) has inserted regiospecifically into the Ir--C(R) bond that bears the CH functionality. Heating solutions of either 2 or 10 in CH(2)Cl(2) allows the formation of the allyl species 3 or 11, respectively, by simple stereoselective migration of the hydride ligand to the Calpha alkenyl carbon atom and concomitant bond reorganization of the resulting organic chain. All the compounds described herein have been characterized by microanalysis, IR and NMR spectroscopy, and for the case of 3, 7, 7CO, 8NCMe, 9, 9NCMe, and 10, also by single-crystal X-ray diffraction studies.

Synthesis of polycyclic nitrogen‐containing heterocyclic: One pot formation of 1,6‐naphthyridine ring system by reaction of amino‐cyano‐methylthio‐heterocycles with dialkyl acetyeledicarboxylates

AbstractReaction of 3‐amino‐3‐methylthio‐2‐cyanoacrylonitrile (1) with excess dimethyl acetylenedi‐carboxylate(DMAD) in the presence of potassium carbonate in dimethyl sulfoxide gave a novel tricyclic heterocycle, hexamethyl lH‐1,4,7‐triazaphenalene‐2,3,5,6,8,9‐hexacarboxylate (5a). When one equivalent of DMAD was used in this reaction, dimethyl 4‐amino‐3‐cyano‐2‐methylthiopyridine‐5,6‐dicarboxylate (3a), a key intermediate of 5a, was obtained.

Syntheses, Structures, and Reactions ofC-Methoxycarbonyl-Functionalized Small- and Medium-Sized P-Heterocycle Complexes

Thermal ring-opening of [{2-bis(trimethylsilyl)methyl-3- phenyl-2H-azaphosphirene-ĸP}pentacarbonyltungsten(0)] (8a) in the presence of dimethyl acetylenedicarboxylate (DMAD) led to the 2,3-bifunctionalized 1H-phosphirene complex 9a and the 4-phenyl-substituted 2H-1,2-azaphosphole complex 10a, the latter as a by-product. If a small amount of benzonitrile was added, complex 10a was obtained as the main product, along with a small amount of the decomplexed 2H-1,2-azaphosphole 11, which could not be isolated. Reaction of complex 10a with elemental sulfur furnished the corresponding PV sulfide 13. When the ring-opening of complex 8a was performed in the presence of two equivalents of DMAD and two equivalents of dimethyl cyanamide, we obtained the 4-dimethylamino-substituted 2H-1,2-azaphosphole complex 10b, together with the diastereomeric Δ3-1,3,2-oxazaphospholene complexes 14a,b. On reaction of [{2-pentamethylcyclopentadienyl-3-phenyl-2H-azaphosphirene-ĸP}pentacarbonyltungsten(0)] (8b) and DMAD in toluene, the corresponding 1H-phosphirene complex 9b was only formed as a transient species and the P-coordinated P,C-cage compound 15 was the final product. Using benzonitrile as solvent, the 4-phenyl-substituted 2H-1,2-azaphosphole complex 10c was obtained, together with the 7-aza-1-phosphanorbornadiene complex 16, the latter through partial decomposition of 10c coupled with rearrangement and a Diels–Alder reaction; the ratio 10c/16 was found to depend strongly on the molar ratio of complex 8b to DMAD. A cycloaddition reaction of the 2,3-bifunctionalized 1H-phosphirene complex 9a with 2,3-dimethylbutadiene furnished the bicyclic phosphirane complex 19, along with a small amount of the noncoordinated bicyclic phosphirane 20. Reaction of complex 9a with diethylamine yielded the phosphirane complex 21 as a 1,2-addition product, the diorganophosphane complex 22 through ring-opening of 9a, and the 3,4-functionalized 1,2-dihydro-1-phosphet-2-one complex 23 through an unprecedented ring-expansion reaction; the products 21, 22, 23 were formed in a ratio of ca. 1:1:1. The structures of the 1H-phosphirene complex 9a, the 4-dimethylamino-substituted 2H-1,2-azaphosphole complex 10b, the bicyclic phosphirane complex 19, the phosphirane complex 21, and the 1,2-dihydro-1-phosphet-2-one complex 23 have been determined by single-crystal X-ray diffraction analysis.

Methoxy-(2-trimethylsilyl)ethoxycarbene. Reactions with Michael acceptors, with hydroxylic compounds, and with miscellaneous functional groups

Methoxy-(2-trimethylsilyl)ethoxycarbene reacts with two equivalents of dimethyl acetylene dicarboxylate, methyl propiolate, phenyl acetylene, or phenyl isocyanate without rearrangement of the carbene group. N-Phenylmaleimide captures the carbene with 1:1 -stoichiometry. The structure of the product implies that a migration of the trimethylsilylethyl group from oxygen to carbon accompanies that reaction. A mechanism for that complex rearrangement is proposed. Phenol and tert-butyl alcohol afford the orthoformates expected from overall insertion of the carbene into the OH bond. Key words: dialkoxycarbene, insertion into O—H, C—H bonds, rearrangement, N-phenylmaleimide, dialkoxyoxadiazoline.

Synthesis of the Novel Tricyclic Heterocycle, 1H-1,4,7-Triazaphenalene, Pyridine-containing Ring System: Hexamethyl 1H-1,4,7-Triazaphenalene-2,3,5,6,8,9-hexacarboxylate

The reaction of 3-amino-3-methylthio-2-cyanoacrylonitrile (1) with excess dimethyl acetylenedicarboxylate(DMAD) in the presence of potassium carbonate in dimethyI sulfoxide gave a novel tricyclic heterocycle, hexamethyl IH-1,4,7-triazaphenalene-2,3,5,6,8,9-hexacarboxylate (5). When one equivalent of DMAD was used in this reaction, dimethyl 4-amino-3-cyano-2-methylthio-pyridine-5,6-dicarboxylate (3), a key intermediate of 5, was obtained

Reactions of 5-cyano-1,4-diphenylpyridazino[4,5-a]indolizines with dimethyl acetylenedicarboxylate: regioselective formation of 1:2 Michael type adducts

Reactions of 5-cyano-1,4-diphenylpyridazino[4,5-a]indolizines with dimethyl acetylenedicarboxylate afforded the 1:2 adducts regioselectively and, unexpectedly, in a Michael fashion rather than in a 1,3-dipolar manner. The structure of the products was established by X-ray crystallography. Regiospecific formation of the observed product 3 can be explained by the higher nucleophilicity of the nitrogen at the 2 position than at the 3 position of the 5-cyano-1,4-diphenylpyridazino[4,5-a]indolizine 1 owing to the contribution of a resonance structure 5 to the hybrid. This favors two successive Michael additions to two equivalents of dimethyl acetylenedicarboxylate affording the observed 1:2 adducts 3.

Synthesis and Structure of a 1λ5,4λ5‐Diphosphapentalene

The diphosphapentalene 3 melts at 194°C without decomposition. Compound 3 is formed in 71% yield by reaction of two equivalents of dimethyl acetylenedicarboxylate (1) with 2. The surprising stability of 3 is due to ylide structures.

ChemInform Abstract: Synthesis of Benzo(ij)cycl(3.3.2)azines via a Palladium‐Mediated Cyclization Reaction.

AbstractTreatment of the dimeric Pd complex (I) with one equivalent of dimethyl acetylenedicarboxylate (II) yields a derivative which is produced by alkyne insertion into the Pd‐C bonds of (I).

ChemInform Abstract: Azaindolizines. Part 7. 7‐Azaindolizines, Their Reactivity and Reaction with Dimethyl Acetylenedicarboxylate.

AbstractCycloaddition reaction of the 7‐azaindolizines (I) with two equivalents of dimethyl acetylenedicarboxylate (II) gives modest yields of the pyrridopyrrolopyridazines (III).

ChemInform Abstract: Reactions of Elemental Sulfur and Selenium with Dimethyl Acetylenedicarboxylate, Methyl Propiolate and Benzyne.

AbstractReaction of selenium with 2 equivalents of dimethyl acetylenedicarboxylate (I) produces the selenophentetracarboxylate (II).

A New Route to Some Novel Phosphole Derivatives

Abstract Previous work has shown that the unstable five co-ordinate phospholes (1; R=alkoxy, R′=alkyl) produced in the reaction of trialkyl phosphites with a two molar equivalent of dimethyl acetylenedicarboxylate can be converted into the novel phospholes (2; R=alkoxy) by treatment with hydrogen bromide at low temperature. We have now shown that a similar approach can be used to generate the phospholes (2; R=alkyl, aryl) by using dialkyl alkylphosphonites or dialkyl arylphosphonites rather than trialkyl phosphites. However, the reduced stability of the phosphorane intermediates (1; R=alkyl, aryl, R′=alkyl) relative to those produced in the trialkyl phosphite reactions means that these trapping reactions are difficult to carry out successfully.