Mechanism of formation of carbene complexes by reaction of cis-[PdCl2(PPh3)(CNR)] with secondary amines

A kinetic study is reported for the reactions of secondary aromatic amines p-YC₆H₄NHR (Y = MeO, Me, H; R = Me, Et) with the isocyanide complexes cis-[PdCl₂(p-XC₆H₄NC)(PPh₃)] (X = Me, H, Cl) leading to the carbene derivatives cis-[PdCl₂ {C(NH-p-C₆H₄X)NR-p-C₆H₄Y} (PPh₃)] in 1,2-dichloroethane at 25°C. A stepwise mechanism is proposed which involves a direct nucleophilic attack of the entering amine on the isocyanide carbon followed by proton transfers to the final carbene complexes. These take place both intramolecularly in a four-membered cyclic transition state and by the agency of one further amine molecule serving as a proton acceptor-donor in a six-membered transition state. Competition experiments with primary amines and trends in rate parameters are discussed to support the mechanism.     

Metallocenyl cations : III. Cymantrenyl carbenium ions containing one phosphine ligand

A number of carbinols, cyclopentadienylmanganese tricarbonyl derivatives of general formula (CO)₂LMnC₅H₄C(OH)RR′ (I) (L = PPh₃ or P(isoC₃H₇)₃, R and R′ = H, Me, Et, Ph) have been synthesised. In solution, in the presence of CF₃COOH they form stable secondary and tertiary carbenium ions, stabilised by the (CO)₂LMnC₅H₄ group. IR spectra and ¹H and ¹³C NMR spectra of the carbenium ions were recorded. Substitution of a tertiary phosphine for a carbonyl group sharply increased the stability of the α-cymantrenylcarbenium ions.     

Spectres de vibration de composes organiques des elements de la colonne IVB : VIII. Derives organometalliques a liaison germanium—azote: Trialkylgermyl-et bis(trialkylgermyl)-amines

We have examined in the 3600–100 cm^?1 region the IR and Raman spectra of three bis(trialkylgermyl)amines (R₃Ge)₂NR′ (R = Me, Et; R′ = H, C₆H₅), of three dialkyl(trialkylgermyl)amines R₃GeNR′₂ (R = Me, Et; R′ = Me, n-Bu) and of two triethylgermylpyrazoles:

Assignments are discussed for the characteristic vibrations of these derivatives.     

Efficient Iminophosphorane‐Mediated Preparation of Benzofuro[3,2‐d]pyrimidin‐4(3H)‐ones and Unexpected Ring Opening Products

The carbodiimides 4 , obtained from aza‐Wittig reactions of iminophosphorane 3 with aromatic isocyanates, reacted with secondary amines, phenols or alcohols in the presence of catalytic amounts of K₂CO₃ or sodium alkoxide to give 2‐substituted benzofuro[3,2‐d]pyrimidin‐4(3H)‐ones 6 . However, when 2,2′‐iminobis[ethanol] was used, the unexpected ring opening product 7 was formed instead of 6 . Reaction of 4 with primary amines RNH₂ (R=Et, Pr, Bu, etc.) gave guanidine intermediates 8 , which were further treated with EtONa to give only one regioisomer 9 via a base catalyzed cyclization. However, another regioisomer 11 was obtained when NH₃ or ‘small’ amines RNH₂ (R=Me, NH₂) were used in the absence of EtONa via a spontaneous cyclization of 8 .     

Darstellung,Eigenschaften und Reaktionsverhalten von 2-(Dimethylaminomethyl)phenyl- und 8-(Dimethylamino)naphthylsubstituierten Lithiumhydridosilylamiden – Bildung von Silaniminen durch Lithiumhydrideliminierung

Preparation, Properties, and Reaction Behaviour of 2-(Dimethylaminomethyl)phenyl- and 8-(Dimethylamino)naphthylsubstituted Lithium Hydridosilylamides – Formation of Silanimines by Elimination of Lithium Hydride The hydridosilylamines Ar(R)Si(H)–NHR′ ( 2 a : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = CMe₃; 2 b : Ar = 2-Me₂NCH₂C₆H₄, R = Ph, R′ = CMe₃; 2 c : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = SiMe₃; 2 d : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = CMe₃; 2 e : Ar = 8-Me₂NC₁₀H₆, R = Ph, R′ = CMe₃; 2 f : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = SiMe₃) have been synthesized from the appropriate chlorosilanes Ar(R)SiHCl either by reaction with the stoichiometric amount of Me₃CNHLi ( 2 a , 2 b , 2 d , 2 e ) or by coammonolysis in liquid NH₃ with chlorotrimethylsilane in molar ratio 1 : 3 ( 2 c , 2 f ). Treatment of 2 a–2 f with n-butyllithium in equimolar ratio in n-hexane resulted in the lithiumhydridosilylamides Ar(R)Si(H)–N(Li)R′ 3 a–3 f . The frequencies of the Si–H stretching vibration and ²⁹Si–¹H coupling constants in the amides are smaller than in the analogous amines indicating a higher hydride character for the hydrogen atom of the Si–H group in the amides compared to the amines. Results of NMR spectroscopic studies point to the existence of a (Me₂)N → Si coordination bond in the 8-(dimethylamino)naphthyl-substituted amines and amides. The amides 3 a–3 c are stable under refluxing in m-xylene. At the same conditions 3 d and 3 e eliminate LiH and the silanimines 8-Me₂NC₁₀H₆(R)Si=NCMe₃ ( 4 d : R = Me, 4 e : R = Ph) are formed. The amides 3 a–3 d und 3 f react with chlorotrimethylsilane in THF to give the corresponding N-substitution products Ar(R)Si(H)–N(SiMe₃)R′ 6 a–6 d and 6 f in good yields. 4 d is formed as a byproduct in the reaction of 3 d with chlorotrimethylsilane. In n-hexane and m-xylene these amides are little reactive opposite to chlorotrimethylsilane. 6 a–6 d and 6 f are obtained in very small amounts. In the case of 3 d besides the N-substitution product 6 d the silanimine 4 d is obtained. In contrast to chlorotrimethylsilane the amides 3 a and 3 f react well with chlorodimethylsilane in m-xylene producing 2-Me₂NCH₂C₆H₄(H) SiMe–N(SiHMe₂)CMe₃ ( 7 a ) and 8-Me₂NC₁₀H₆(H)SiMe–N(SiHMe₂)SiMe₃ ( 7 f ).     

Vinylacetylene chemistry

It is shown that heating vinylacetylenic piperidols I with phosphorus oxychloride in pyridine solution gives dienynes II, the structure of which is determined, in the case of II (R=H), by means of IR spectra and PMR. Hydration of the dienynes II (R=H, Me) in the presence of mercuric sulfate in methanol solution gives -methoxyketones III (R=H, Me). It is also shown that III and aqueous solutions of ammonia or primary amines give the bicyclic piperid-4-ones IV. In the synthesis of IV (R=H, R₁ = i-Pr, Bu) imines V are obtained, which on hydrolysis give piperidones IV (R = H, R₁ = i-Pr, Bu). When the ß-methoxyketone III (R = H) is heated with 5% sulfuric acid in the presence of mercuric sulfate, chroman-4-one is formed.     

Studies of phosphazenes. Aminolysis reactions of pentachloro(2′, 2′, 2′-triphenyl-phosphazen-1′-yl) cyclotriphosphazene,N3P3Cl5(NPPh3)

The reactions of pentachloro(2′, 2′, 2′-triphenylphosphazen-1′-yl)cyclotriphosphazene, N₃P₃Cl₅(NPPh₃), with primary and secondary amines have been investigated using diethyl ether, methyl cyanid or benzene as the solvent. The structures of the products obtained, N₃P₃Cl_5minus;nR_n(NPPh₃) [n = 1, R = NHMe, NHBu^t, NMe₂, NC₅H₁₀, NEt₂; n = 2, R = NMe₂, NC₅H₁₀, NEt₂; n = 3, R = NMe₂, NHBu^t; n = 5, R = NMe₂] are elucidated by ¹H and ³¹P NMR spectroscopy. The ? NPPh₃ substituent exerts a pronounced geminal directing influence on incoming secondary amino nucleophiles; compounds containing a ≡ PCl(NPPh₃) group are not formed at the bis and subsequent stages of chlorine replacement. The reactions that involve primary amines follow the pattern established for the analogous reactions of hexachlorocyclotriphosphazene. The effect of solvent and possible mechanism(s) are discussed.     

Pt-Sn/γ-Al2O3-catalyzed highly efficient direct synthesis of secondary and tertiary amines and imines

Versatile syntheses of secondary and tertiary amines by highly efficient direct N‐alkylation of primary and secondary amines with alcohols or by deaminative self‐coupling of primary amines have been successfully realized by means of a heterogeneous bimetallic Pt–Sn/γ‐Al₂O₃ catalyst (0.5 wt % Pt, Pt/Sn molar ratio=1:3) through a borrowing‐hydrogen strategy. In the presence of oxygen, imines were also efficiently prepared from the tandem reactions of amines with alcohols or between two primary amines. The proposed mechanism reveals that an alcohol or amine substrate is initially dehydrogenated to an aldehyde/ketone or NH‐imine with concomitant formation of a [PtSn] hydride. Condensation of the aldehyde/ketone species or deamination of the NH‐imine intermediate with another molecule of amine forms an N‐substituted imine which is then reduced to a new amine product by the in‐situ generated [PtSn] hydride under a nitrogen atmosphere or remains unchanged as the final product under an oxygen atmosphere. The Pt–Sn/γ‐Al₂O₃ catalyst can be easily recycled without Pt metal leaching and has exhibited very high catalytic activity toward a wide range of amine and alcohol substrates, which suggests potential for application in the direct production of secondary and tertiary amines and N‐substituted imines.     

Neue Aminometallane des Aluminiums und Galliums

New Aminometalanes of Aluminum and Gallium The reaction of secondary amines R′RNH with trimethyaluminum leads to the formation of dimeric aminoalanes [RR′NAlMe₂]₂ ( 1 ) (R = 2,6-Me₂C₆H₃, R′ = SiMe₂(2,4,6-Me₃C₆H₂)) and 2 (R = Ph, R′ = SiMe₃). Using a different stoichiometric ratio, a monomeric aminoalane [RR′N]₂AlMe ( 3 ) (R = Ph, R′ = SiPh₂Me) is obtained, having an aluminum atom of coordination number three due to the steric demand of the substituents. The synthesis of the corresponding aminogallanes 4 , 5 and 6 is achieved by reaction of lithium amides LiNRR′ (R = Ph, 2,6-iPr₂C₆H₃; R′ = SiMe₃, SiMe₂iPr) with dimethylgalliumchloride, Me₂GaCl, in n-hexane. The formation of the dimeric species is in 1 through carbon while that in 2 and 3 is formed through nitrogen. The X-ray single crystal structure analysis of 1 , 2 , 3 and 4 are reported.     

Ruthenium-catalysed synthesis of tertiary amines from alcohols

Secondary amines have been converted into tertiary amines by reactions with primary alcohols. A catalytic system of [Ru(cymene)Cl₂]₂ with dppf has been shown to be effective for this transformation for a range of primary alcohols and secondary amines. The methodology has been applied to the one pot synthesis of Piribedil and other piperazine and morpholine-containing products.     

Diorganotin(IV) and triorganotin(IV) derivatives of diphenic acid

The diorganotin(IV) and triorganotin(IV) derivatives R₂SnA (R = Me, n-Pr, n-Bu, n-Oct) and (R₃Sn)₂A [R = Me, Ph, cyclohexyl (Cyh); A = an anion of diphenic acid] have been prepared and characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopies. Tetrahedral tin forms a part of a diphenate cyclic ring in the diorganotin complexes with unidentate carboxylates, which have further been used for the synthesis of cyclic acid anhydrides. The soluble dinuclear triorganotin complexes (Me, Ph) possess symmetrically bonded carboxylates while the less soluble compound (Cyh₃Sn)₂A has two asymmetrically bonded carboxylates. All have a trigonal bipyramidal structure with R₃Sn units remote from each other.     

Alcoholate Complexes of Nickel(II) Chloride

Alcoholate complexes of nickel chloride with the general formula, NiCL₂ · ROH (R = CH₃, C₂H₅, i-C₃H₇, n-C₄H₉, t-C₄H₉, t-C₅H₁₁, n-C₆H₁₃ and n-C₈H₁₇), synthesized either by the reaction of anhydrous nickel chloride with alcohols or by the replacement of methanol from NiCL₂ · MeOH with higher alcohols, depict interesting differences when R is a secondary or tertiary alkyl group instead of a primary group. A study of the magnetic susceptibility, thermogravimetric measurement, electron spin resonance and electronic reflectance spectra has been carried out to throw light on the structure of these derivatives.     

Über Cyanatverbindungen und deren reaktives Verhalten. XXI. Reaktionsverhalten von Niob(V)- und Tantal(V)-thiocyanat gegenüber N-Donatoren

Cyanate Compounds and their Reactivity. XXI. Reactivity of Niobium(V) and Tantalum(V) Thiocyanates to N-Donators M₂(NCS)₁₀ reacts with ammonia or primary and secondary aliphatic amines to complexes of the types [M(NCS)(NH₂)₂NH]_x, [M(NCS)₃(NHR)₂ H₂NR], or [M(NCS)₃(NR′₂)₂ HNR′₂], with N-heterocyclic amines in a first step to [M(NCS)₅L]-complexes and in a further step through a redox mechanism to [M(NCS)₄L₂] complexes. [M(NCS)₅(CH₃CN)] mCH₃CN reacts with ammonia, or primary amines in acetonitrile over acetamidine and amidinolytic cleavage of M-NCS bonds to complexes of the type [M(NCS)_a(NC(NHR″)CH₃)_b(CH₃C(NH)NHR″)]_x. The prepared compounds are characterized by analytical data, derivatographic measurements, and IR or visible absorption spectra (M = Nb, Ta; x = 2; R = n-C₄H₉; R′ = C₂H₅; L = pyridine or 4-methyl-pyridine; m = 0, 1, 2; a = 1 or 4; b = 4 or 1; R″ = H, n-C₄H₉).     

Steric effects in palladium-catalysed amination of aryl triflates and nonaflates with the primary amines PhCH(R)NH2 (R=H, Me)

A systematic study of the effects of aryl triflate and nonaflate structure on the yield of amination with the primary amines PhCH(R)NH₂ (R=H, Me) under palladium catalysis has been carried out. High throughput screening indicated that a catalyst composed of X-Phos/Pd₂(dba)₃/1,4-dioxane was optimal based on a model reaction of Ar(OR_f) [R_f=Tf (SO₂CF₃), Nf (SO₂(CF₂)₃CF₃)] with PhCH₂NH₂. Comparisons of the reactivity of various ArOTf and ArONf [Ar=4-MePh, 2-naphthyl, 1-naphthyl, 2-PhC₆H₄] indicated that both ortho substitution in the aryl electrophile and at the α-position on the amine are detrimental to the coupling particularly when they occur in combination. Despite being formally a monodentate ligand use of X-Phos leads to only small degrees of racemisation when using (R)-PhCH(Me)NH₂ (typically resulting in a reduction from 97 to 86-94% ee for the amine stereocentre).     

Darstellung und oxidative Derivatisierung von Dialkylthiophosphiten

Preparation and Oxidative Derivatisation of Phosphonothionic Esters The kind of the amine used influences decisively course and rate of the reaction of trialkyl phosphites, (RO)₃P (R = Me, Et, Ph) with H₂S in the presence of different amines (Et₃N, Et₂NH, Et₂NPh, pyridine). Phosphonothionic esters, (RO)₂P(S)H (R = Me, Et, Bu), are obtained in over 80% yield by using pyridine as base and an alkali alcoholate as catalyst. The oxidative derivatisation of phosphonothionic esters by means of CCI₄ and protic (4-nitrophenol, 2,4,5-trichlorophenol, ammonia, piperidine, phenylhydrazine) or anionic nucleophiles (F^?, NCS^?, NCO^?, CN^?, N₃^?) (Atherton-Todd reaction) yields thiophosphoric acid derivatives (RO)₂P(S)Nuc (R = Me, Et, Bu: Nuc = 4-nitrophenoxy, PhNHNH; R = Me, Et: Nuc = 2,4,5-trichlorophenoxy, F, NCS, N₃; R = Me: NH₂, C₅H₁₀N; R = Et: Nuc = CI, CN) and in some cases the dealkylated products (RO)P(Nuc)SO^? (R = Me; Nuc = CI, F, NCS, CN). The phosphazenes (EtO)₂P(S)? N = PPh₃ and (MeO)₂P(S)? N ? P(OEt)₃, up to now unknown in literature, were obtained by treating thiophosphoryl azides with PPh₃ or P(OEt)₃, resp.     

L'hydrolyse acide des diazocétones alcoylées: Formation d'ions α-acylcarbonium secondaires

Hydrolysis of secondary diazoketones CH₃? CO? CN₂? R (R ? Me, Et, isopropyl) by aqueous perchloric acid is characterized by rate-determining protonation demonstrated by solvent isotope effects kD₂O/kH₂O = 0,4–0,6 and by the intervention of general acid catalysis. The product determining step, yielding keto-alcohols and keto-olefines, is independent of added nucleophiles; this is interpreted as resulting from the intermediate formation of (more or less free) αhyphen;ketocarbonium is ions. The hydride shift observed wih III (R = isopropyl) supports this interpretation. The difference between hydrolysis of primary and of secondary diazoketones is discussed.     

Characterization of bis(alkylamine)mercury cations from mercury nitrate surfaces by using an ion trap secondary ion mass spectrometer

Mercury-cyclohexylamine (R-NH₂, where R = c-C₆H₁₁) ions having the composition Hg(R-NH)₂H⁺ can be formed by exposing the surface of Hg(NO₃) _{n = 1,2} salts to gaseous primary amines and then sputtering the surface with a primary ion beam (ReO ₄ ^? ). The resultant ions can be stabilized and detected using an ion trap secondary ion mass spectrometer (IT-SIMS) instrument, which provides collisional stabilization that facilitates their observation. Isolation of the Hg(R-NH)₂H⁺ ions followed by collisional activation produces daughter ions corresponding to (C₆H₁₀NH₂)⁺ and Hg(R-NH)⁺. These assignments were supported by deuterium labeling experiments, which resulted in the formation of Hg(R-NH)(R-NH-d ₁₁)H⁺ and Hg(R-NH)₂H⁺. The existence of the Hg(R-NH)₂ compounds on the surface was verified using Raman spectroscopy, which showed a strong absorption at 590 cm^?1 that corresponded to Hg-N stretching. Analogous ions could be formed with n-hexylamine, but no Hg-bearing ions were formed when starting with a secondary or a tertiary amine. This indicates that only primary amines will react with Hg-nitrate surfaces in this manner. Hg-amine ions could not be formed starting with other Hg salts: chloride, iodide, thiocyanate, sulfate, and oxide. These results suggest that surface derivatization using amines, coupled with an IT-SIMS instrument, may offer an approach for determining inorganic metal speciation on surfaces.     

Palladium Complexes Based on Ylide-Functionalized Phosphines (YPhos): Broadly Applicable High-Performance Precatalysts for the Amination of Aryl Halides at Room Temperature

Palladium allyl, cinnamyl, and indenyl complexes with the ylide-substituted phosphines Cy₃P⁺−C⁻(R)PCy₂ (with R=Me ( L1 ) or Ph ( L2 )) and Cy₃P⁺−C⁻(Me)PtBu₂ ( L3 ) were prepared and applied as defined precatalysts in C−N coupling reactions. The complexes are highly active in the amination of 4-chlorotoluene with a series of different amines. Higher yields were observed with the precatalysts in comparison to the in situ generated catalysts. Changes in the ligand structures allowed for improved selectivities by shutting down β-hydride elimination or diarylation reactions. Particularly, the complexes based on L2 (joYPhos) revealed to be universal precatalysts for various amines and aryl halides. Full conversions to the desired products are reached mostly within 1 h reaction time at room temperature, thus making L2 to one of the most efficient ligands in C−N coupling reactions. The applicability of the catalysts was demonstrated for aryl chlorides, bromides and iodides together with primary and secondary aryl and alkyl amines, including gram-scale applications also with low catalyst loadings of down to 0.05 mol %. Kinetic studies further demonstrated the outstanding activity of the precatalysts with TOF over 10.000 h⁻¹.     

Synthesis and characterization of pentagonal bipyramidal organotin(IV) complexes of 2,6-diacetylpyridine Schiff bases of S-alkyl- and aryldithiocarbazates

New organotin(IV) complexes with empirical formula Sn(SNNNS)R₂, where SNNNS is the dianionic form of 2,6-diacetylpyridine Schiff bases of S-methyldithiocarbazate (H₂dapsme) or S-benzyldithiocarbazate (H₂dapsbz) and R = Ph or Me, have been prepared and characterized by IR, UV-Vis, NMR and Mössbauer spectroscopic techniques and conductance measurements. The molecular structures of the Sn(dapsme)R₂ (R = Ph and Me) have been determined by single crystal X-ray diffraction techniques. Both complexes have a distorted pentagonal-bipyramidal geometry in which the tin is coordinated by a dinegatively charged pentadentate chelating agent via pyridine nitrogen, two azomethine nitrogens, and two thiolate sulfurs. The five donors (N₃S₂) provided by the Schiff base occupy the equatorial plane close to a pentagonal planar array while the carbanion ligands occupy axial sites.     

CpIr-catalyzed N-alkylation of amines with alcohols. A versatile and atom economical method for the synthesis of amines

A versatile and highly atom economical catalytic system consisting of [Cp^∗IrCl₂]₂/NaHCO₃ (Cp^∗=pentamethylcyclopentadienyl) for the N-alkylation of amines with primary and secondary alcohols as alkylating reagents has been developed. For example, the reaction of equimolar amounts of aniline and benzyl alcohol in the presence of [Cp^∗IrCl₂]₂ (1.0 mol % Ir) and NaHCO₃ (1.0 mol %) in toluene at 110 °C gives N-benzylaniline in 94% yield. The present catalytic system is applicable to the N-alkylation of both primary and secondary amines, and only harmless water is produced as co-product. A wide variety of secondary and tertiary amines can be synthesized with high atom economy under mild and less-toxic conditions. One-pot sequential N-alkylation leading to tertiary amines bearing three different substituents is also described.