An NHC-Stabilized H2GeBH2 Precursor for the Preparation of Cationic Group 13/14/15 Hydride Chains

The synthesis, characterization and reactivity studies of the NHC-stabilized complex IDipp ⋅ GeH₂BH₂OTf ( 1 ) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) are reported. Nucleophilic substitution of the triflate (OTf) group in 1 by phosphine or arsine donors provides access to the cationic group 13/14/15 chains [IDipp ⋅ GeH₂BH₂ERR¹R²]⁺ ( 2 E=P; R, R¹=H; R²=^tBu; 3 E=P; R=H; R¹, R²=Ph; 4 a E=P; R, R¹, R²=Ph; 4 b E=As; R, R¹, R²=Ph). These novel cationic chains were characterized by X-ray crystallography, NMR spectroscopy and mass spectrometry. Moreover, the formation of the parent complexes [IDipp ⋅ GeH₂BH₂PH₃][OTf] ( 5 ) and [IDipp ⋅ GeH₃][OTf] ( 6 ) were achieved by reaction of 1 with PH₃. Accompanying DFT computations give insight into the stability of the formed chains with respect to their decomposition.     

1,3,4-Oxa- und 1,3,4-Thia-diphospholane aus Diphosphorsubstituierten 2-Oxa- und 2-Thia-propanen

1,3,4-Oxadiphospholanes and 1,3,4-Thiadiphospholanes from Diphosphorus-substituted 2-Oxa- and 2-Thia-propanes The synthesis of phosphonates and phosphinates of the type (RO)₂(O)PCH₂ZCH₂P(O)(OR)₂, R¹(RO)(O)PCH₂ZCH₂P(O)(OR)₂ and R¹(RO)(O)PCH₂ZCH₂P(O)(OR)R¹ (with Z = O, S; R = Et, Prⁱ; R¹ = Me, Ph) is reported. Acyclic diphosphanes, R¹(H)PCH₂ZCH₂P(H)R² (with Z = O, S; R¹ = R² = H, Me, Ph; R¹ = H, R² = Me), and 1,3,4-Oxadiphospholanes as well as 1,3,4-Thiadiphospholanes are obtained from the esters by reduction.     

η2-Phosphasilene transition metal complexes – a novel building block for hetero-multimetallic complexes

Compound η²-((R₃Si)₂Si=PH)–Pt(dmpe) was synthesized by trapping the transient phosphasilene, (R₃Si)₂Si=PH. Novel hetero-bi- and tri-metallic complexes derived from η²-((R₃Si)₂Si=PH)–Pt(dmpe) containing Pt with Li, Zn, Hg and Ag metals were synthesized and characterized by multi- nuclear NMR spectroscopy and X-ray crystallography. The synthesis of η²-((R₃Si)₂Si=PH)–Pt(dmpe), and its bonding character are discussed; a 1,2-silyl shift from silicon to phosphorus (a ‘Brook-type’ rearrangement) within the coordination sphere of a Pt complex is also reported.     

A New Synthesis of 3-Aryl-5-Arylmethylene-2(5H)-Furanones

A recent report about the synthesis of di and tri-substituted 2 (5H)-furanones starting from bromoaldehydes and potassium phenyl-acetate¹ prompts us to report our own studies on the preparation of 3-aryl-5-arylmethylene-2 (5H)-furanones (or butenolides) 1. We have earlier reported² a general method for the synthesis of 1 from phenylpropargyl aldehyde, 2 and arylacetic acids. Although several methods have been reported for the synthesis of the parent compound 1 (R = R₁ = Ph)^3–6, these methods have not been extended to other substituted furanones. Saikachi and Taniguchi⁷ prepared 1 (R = 5-nitro-2-thenyl, R₁ = 2-thenyl and 2-furyl) in 16–17% yields.     

Synthesis of 4‐(trihalomethyl)dipyrimidin‐2‐ylamines from β‐alkoxy‐α,β‐unsaturated trihalomethyl ketones

The synthesis of a novel series of twelve 4‐(trihalomethyl)dipyrimidin‐2‐ylamines, from the cyclo‐condensation reaction of 4‐(trichloromethyl)‐2‐guanidinopyrimidine, with β‐alkoxyvinyl trihalomethyl ketones, of general formula: X₃C‐C(O)‐C(R²)=C(R¹)‐OR, where: X = F, Cl; R = Me, Et, ‐(CH₂)₂‐, ‐(CH₂)₃‐; R¹ = H, Me; R² = H, Me, ‐(CH₂)₂‐, ‐(CH₂)₃‐, is reported. The reactions were carried out in acetonitrile under reflux for 16 hours, leading to the dipyrimidin‐2‐ylamines in 65‐90% yield. Depending on the substituents of the vinyl ketone, tetrahydropyrimidines or aromatic pyrimidine rings were obtained from the cyclization reaction. When X = Cl, elimination of the trichloromethyl group was observed during the cyclization step. The structure of 4‐(trihalomethyl)dipyrimidin‐2‐ylamines was studied in detail by ¹H‐, ¹³C‐ and 2D‐nmr spectroscopy.     

Hydrogenation of β-Keto Sulfones to β-Hydroxy Sulfones with Alkyl Aluminum Compounds: Structure of Intermediate Hydroalumination Products

β-Hydroxy sulfones are important in organic synthesis. The simplest method of β-hydroxy sulfones synthesis is the hydrogenation of β-keto sulfones. Herein, we report the reducing properties of alkyl aluminum compounds R₃Al (R = Et, i-Bu, n-Bu, t-Bu and n-Hex); i-Bu₂AlH; Et₂AlCl and EtAlCl₂ in the hydrogenation of β-keto sulfones. The compounds i-Bu₂AlH, i-Bu₃Al and Et₃Al are the at best reducing agents of β-keto sulfones to β-hydroxy sulfones. In reactions of β-keto sulfones with aluminum trialkyls, hydroalumination products with β-hydroxy sulfone ligands [R₂AlOC(C₆H₅)CH₂S(O)₂(p-R¹C₆H₄]_n [where n = 1,2; 2aa: R = i-Bu, R¹ = CH₃; 2ab: R = i-Bu, R¹ = Cl; 2ba: R = Et, R¹ = CH₃; 2bb: R = Et, R¹ = Cl] and {[Et₂AlOC(C₆H₅)CH₂S(O)₂(p-ClC₆H₄]∙Et₃Al}_n 3bb were obtained. These complexes in the solid state have a dimeric structure, while in solutions, they appear as equilibrium monomer–dimer mixtures. The hydrolysis of both the isolated 2aa, 2ab, 2ba, 2bb and 3bb and the postreaction mixtures quantitatively leads to pure racemic β-hydroxy sulfones. Hydroalumination reaction of β-keto sulfones with alkyl aluminum compounds and subsequent hydrolysis of the complexes is a simple and very efficient method of β-hydroxy sulfones synthesis.     

Bis(arylimido) Molybdenum(VI) Amidinate and Guanidinate Complexes; Molecular Structures of [(ArN)2MoMe{N(Cy)C[N(i‐Pr)2]N(Cy)}] (Ar = 2,6‐i‐Pr2C6H3; Cy = Cyclohexyl) and [(2,6‐i‐Pr2C6H3N)2MoCl2] · [NH=C(C6H5)CH(SiMe3)2]

The reaction of [(ArN)₂MoCl₂] · DME (Ar = 2,6‐i‐Pr₂C₆H₃) ( 1 ) with lithium amidinates or guanidinates resulted in molybdenum(VI) complexes [(ArN)₂MoCl{N(R¹)C(R²)N(R¹)}] (R¹ = Cy (cyclohexyl), R² = Me ( 2 ); R¹ = Cy, R² = N(i‐Pr)₂ ( 3 ); R¹ = Cy, R² = N(SiMe₃)₂ ( 4 ); R¹ = SiMe₃, R² = C₆H₅ ( 5 )) with five coordinated molybdenum atoms. Methylation of these compounds was exemplified by the reactions of 2 and 3 with MeLi affording the corresponding methylates [(ArN)₂MoMe{N(R¹)C(R²)N(R¹)}] (R¹ = Cy, R² = Me ( 6 ); R¹ = Cy, R² = N(i‐Pr)₂ ( 7 )). The analogous reaction of 1 with bulky [N(SiMe₃)C(C₆H₅)C(SiMe₃)₂]Li · THF did not give the corresponding metathesis product, but a Schiff base adduct [(ArN)₂MoCl₂] · [NH=C(C₆H₅)CH(SiMe₃)₂] ( 8 ) in low yield. The molecular structures of 7 and 8 are established by the X‐ray single crystal structural analysis.     

Schwefeldioxid als Ligand und Synthon. XII. Synthese und Reaktivität von Nickel(II)-Komplexen dreizähniger anionischer Liganden des Typs (C6H3{CH2NR1R2}2-2,6)−

Sulfur Dioxide as Ligand and Synthon. XII. Synthesis and Reaction Behaviour of Nickel(II) Complexes with Terdendate Anionic Ligands of the Type (C₆H₃{CH₂NR¹R²}₂?2,6)^? Organonickel(II) complexes of the type [NiX{C₆H₃(CH₂NR¹R²)₂?2,6}] (X = halide OH₂⁺/CF₃SO₃^?; R¹?R²?Et 1 ; R¹?R²?i? Pr 2 ; R¹ = Me, R² = Cy 3 ; (NR¹R²) = piperidino 4 ; (NR¹R²) = pyrrolidino 5 ) are described. ¹H and ¹³C NMR and UV/Vis spectra were recorded, and the X-ray crystal structure of 1 a (X = Br) was determined. This complex crystallizes orthorhombically in the space group Pbca with a = 1 335.8(2) pm, b = 1 903.3(3) pm, c = 1 365.4(3) pm and Z = 8, and has an approximately square-planar geometry. 4 and 5 show a reversible binding of SO₂ which has been detected by means of IR photoacoustic spectroscopy. The reactions of 1 – 5 with CS₂ and PhNSO are discussed.     

Dissociation constants of 2‐azidoethanamines in aqueous solution

Aqueous‐phase dissociation constants (K_a) for the conjugate acids of a series of 2‐azidoethanamine bases: R¹N(R²)CH₂CH₂N₃ ( 1 , R¹ = CH₃, R² = H; 2 , R¹ = CH₃, R² = CH₃; 3 , R¹ = CH₂CH₃, R² = CH₂CH₃; 4 , R¹/R² =  CH₂CH₂CH₂CH₂ ; 5 , R¹/R² =  CH₂CH₂OCH₂CH₂ ; 6 , R¹ = CH₂CH₃, R² = CH₂CH₂N₃) were measured and found to fall between those for analogous unfunctionalized and cyano‐functionalized ethanamines. To explore the possibility of a relationship existing between the constants and molecular geometry, a theoretically based study was conducted. In it, the Gibbs free energies of aqueous‐phase (equilibrium) conformers of the bases and their conjugate acids were determined via a density functional theory/polarizable continuum model method. The results indicate that an attractive interaction between the amine and azide groups that underlies the lowest‐energy gas‐phase conformer of 2 is negated in an aqueous environment by solvent–solute interactions. The magnitudes of the free energy changes of solvation and −TS (entropic) energies of the conformers of the 2‐azidoethanamines and their conjugate acids are observed to correlate with the magnitude of the separation between the conformers' amine and azide groups. However, those correlations are not by themselves sufficient to predict the relative free energies of a molecule's conformers in an aqueous environment. That insufficiency is due to the influence of the correlations being mitigated by three other parameters that arise within the thermodynamic framework employed to compute the observable. The nature of those parameters is discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Phosphoniumsalze mit Hydrogendihalogenidanionen HCl2−, HBr2− Hl2− oder HBrCl−

Phosphonium Salts with Hydrogen Dihalide Anions HCl₂^?, HBr₂^?, HI₂^?, or HBrCl^? Phosphonium hydrogen dihalides [R₃PR′][XHY] (X = Y = Cl, Br, I; X = Br, Y = Cl) resp. [R₃PH]HBr₂ are obtained as extremely hydrolyzable crystals by reaction of phosphonium halides or tertiary phosphanes with hydrogen halide. According to IR spectroscopic results the solid compounds mostly contain anions [XHX]^? with symmetric hydrogen bonds. In solution ¹H NMR measurements show a slight (X = Cl, Br) or considerable (X = I) dissociation according to HX₂^? ? X^? + HX. On heating the solid compounds decompose with formation of hydrogen halide and [R₃PR′]X or [R₃PH]X. In this process the hydrogen bromidechlorides [R₃PR′][BrHCl] exclusively eliminate HCl. NMR studies (¹H und ³¹P) with solutions containing [R₃PH]HBr₂ (R = phenyl, 1-naphtyl) or HBr and Ph₃P in varying molar ratios show that a fast proton exchange between the competing Lewis bases R₃P and Br^? exists.     

New one-pot, efficient, and regioselective method for the synthesis of 3-Trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs

An efficient and regioselective procedure for the synthesis of a series of alkyl(aryl/heteroaryl) substituted 3-trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs, from the cyclocondensation reactions of 4-alkoxy-1,1,1-trihaloalk-3-en-2-ones [CX₃C(O)CR²=CR¹(OMe/OEt), where R¹ = H, Me, Ph, 2-Furyl; R² = H; R¹-R² = -C₄H₈- and X = F, Cl] and 1-phenylsemicarbazide in an acidified alcoholic medium (R³OH/H₂SO₄), where R³ = Me, Et, Prⁱ was successfully applied and is described here in detail.     

Combinatorial Solid-Phase Synthesis of Structurally Complex Thiazolylhydantoines

A nine-step (!) solid-phase synthesis and subsequent cleavage with cyclization from the polymeric support were the keys to preparing high-quality molecular libraries of thiazolylhydantoines 1 from modified amino acid building blocks. Each step in the synthesis is different. Because the final cyclization cleaves only molecules that have been successfully constructed, the products obtained are pure. R¹, R²=alkyl; R³=aryl, arylO; R⁴=allyl.     

Spectroscopic studies of biologically active organotin(IV) derivatives of 2-[N-(2,4,6-tribromophenylamido]propanoic acid

Herein we describe the synthesis and characterization of compounds having the formulae R₂SnL₂ and R₃SnL, where R = Me, n-Bu, Ph and n-Oct and L = 2-[N-(2,4,6-tribromophenylamido]propanoic acid. All the complexes have been characterized by various spectroscopic methods (IR and ¹H, ¹³C, ¹¹⁹Sn NMR), elemental analysis, mass spectrometry and physical data. These compounds were also screened for their biological activity and found some encouraging results.     

Über den Phosphandiyl‐Transfer von invers‐polarisierten Phosphaalkenen R1P=C(NMe2)2 (R1 = tBu,Cy, Ph,H) auf Phospheniumkomplexe [(η5‐C5H5)(CO)2M=P(R2)R3] (R2 = R3 = Ph; R2 = tBu,R3 = H; R2 = Ph,R3 = N(SiMe3)2)

Phosphanediyl Transfer from Inversely Polarized Phosphaalkenes R¹P=C(NMe₂)₂ (R¹ = tBu, Cy, Ph, H) onto Phosphenium Complexes [(η⁵‐C₅H₅)(CO)₂M=P(R²)R³] (R² = R³ = Ph; R² = tBu, R³ = H; R² = Ph, R³ = N(SiMe₃)₂) Reaction of the freshly prepared phosphenium tungsten complex [(η⁵‐C₅H₅)(CO)₂W=PPh₂] ( 3 ) with the inversely polarized phosphaalkenes RP=C(NMe₂)₂ ( 1 ) ( a : R = tBu; b : Cy; c : Ph) led to the η²‐diphosphanyl complexes ( 9a‐c ) which were isolated by column chromatography as yellow crystals in 24‐30 % yield. Similarly, phosphenium complexes [(η⁵‐C₅H₅)(CO)₂M=P(H)tBu] (M = W ( 6 ); Mo ( 8 )) were converted into (M = W ( 11 ); Mo ( 12 )) by the formal abstraction of the phosphanediyl [PtBu] from 1a . Treatment of [(η⁵‐C₅H₅)(CO)₂W=P(Ph)N(SiMe₃)₂] ( 4 ) with HP=C(NMe₂)₂ ( 1d ) gave rise to the formation of yellow crystalline ( 10 ). The products were characterized by elemental analyses and spectra (IR, ¹H, ¹³C‐, ³¹P‐NMR, MS). The molecular structure of compound 10 was elucidated by an X‐ray diffraction analysis.     

Electron impact induced fragmentations of 2-chlorovinyl methyl sulphides

A series of 2-chlorovinyl methyl sulphides, CH₃SCR¹?CR²Cl (R¹, R² = H, Me, Et, t-Bu, Ph; R¹ = H, R² = CH₃) has been analysed under electron impact conditions. The most significant common fragmentations involve primary loss of Cl˙ and methyl radicals. Analysis of the phenyl-substituted derivative suggests that loss of CH₃˙ is a lower activation energy process than loss of Cl˙. The characteristic loss of CH₃SCl from the same derivative has been examined with respect to the structure of the resulting fragment by means of suitable model compounds.     

Reactions of β-nitrostyrenes with tert-butylmercury halides in the presence of lodide lon

Photolysis of t-BuHgCl/KI with PhC(R²)C(R¹)NO₂ forms PhC(R²)C(R¹)Bu-t when R¹ = R² = H or in low yield when R¹ = H, R² = Ph. When R¹ ≠ H, or when R² = Ph, reactions with t-BuHgI/KI/hv proceed mainly via PhC(R²)C(R¹)NO₂·-, PhC(R²)C(R¹)N(OBu-t)O⁻HgX⁺, PhC(R²)C(R¹)NO and PhC(R²)C(R¹)N(OBu-t)HgX to form a variety of novel products including the dimeric bisnitronic esters ( 6 ) with R¹ = Me or Ph and R² = H; PhCH(R²)C(R¹) = NOBu-t with R¹ = Me or Ph and R² = H or R¹ = H and R² = Ph; PhC(R²)(OBu-t)C(R¹)NOH with R¹ = H or Me and R² = Ph; and 3-phenyl-2-R¹-indoles with R¹ = H, Me, Ph, PhS or t-BuS and R² = Ph. Nitrosoaromatics react with t-BuHgX in the dark to form ArN(OBu-t)(OBu-t)HgX⁺ which condenses with ArNO to form the azoxy compound. tert-Butyl radicals will add to RNO₂ [R = Ph, Ph₂CCH, Ph₂CC(Ph)] in the presence of t-BuHgI₂⁻ to form products derived from RN(OBu-t)O⁻HgI⁺.     

Synthesis and Structural Characterization of a Novel Indium Mercapto Derivative [ClIn(SCH2(CO)O)2]2-[(4-MepyH)2]2+

The synthesis and structural characterization of a novel In(III) complex is described. The reaction between InCl₃ with sodium mercapto-acetic acid (NaSCH₂(CO)OH) in 4-methylpyridine (CH₃(C₅H₅N), (4-Mepy)) at 25°C affords [ClIn(SCH₂(CO)O)₂]^2-[(4-MepyH)₂]²⁺ (1). X-ray diffraction studies of (1) show it to have a distorted square-pyramidal geometry with the [(^-SCH₂(CO)CO^-)] ligands in a trans conformation. The compound crystallizes in the P1(No. 2) space group with a = 7.8624(6) Å, b = 9.950(1) Å, c = 13.793(2) Å, α = 107.60(1)°, β = 90.336(8)°, γ = 98.983(9)°, V = 1014.3(4) ų, R(F°) = 0.037 and R_w = 0.048.     

1,2-dihydro-1,2,4,3-triazaphospholo[4,5-a]quinolines as electron carriers in the electrochemical reduction of 1,1-dichloro-2-methoxycarbonyl-2-methylcyclopropane

Electrochemical reduction of 1-X-1-R¹-5-methyl-2-phenyl-7-R²-1,2-dihydro-1,2,4,3-tri-azaphospholo[4,5-a]quinolines1–5 (1: X is the lone electron pair (LEP), R¹=Et₂N, R²=Me;2: X=LEP, R¹=Ph, R²=H;3: X=S, R¹=Et₂N, R²=H;4: X=LEP, R¹=Et₂N, R²=H;5: X=LEP, R¹=MeO, R²=H) in DMF with 0.1M Bu₄NI as supporting electrolyte is reversible and results in metastable radical anions. Radical anions of compounds1–3 efficiently reduce 1,2-dichloro-2-methoxycarbonyl-2-methylcyclopropane both in the presence and in absence of Ni¹¹ ions. Effective reduction rate constants have been evaluated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 1999.     

METALLOLES-14 CHEMISTRY

Abstract

In order to obtain β-functionalized 1-sila (or germa)-cyclopent-2-enes (M = Si, Ge; R¹, R² = Me or Ph; R³, R⁴ = H or Me) (I) various oxidation methods of metallacyclopent-3-enes have been examinated. The resulting metallacyclopent-4-ene-3-ols (I, X = OH) were converted into phenylcarbamates (I = OC(O)NHPh) or S-methylxanthates (I = OC(S)SMe) and their utility as intermediates in the synthesis of metalloles (siloles and germoles) was investigated.

Depending on the experimental conditions, catalytic dehydration of metallacyclopentenols or thermolysis of carbamates or xanthates give various dienes via four different reaction processes: i) β-elimination C-M; ii) β-elimination C-H; iii) isomerization of C-methylated metalloles; iv) catalytic demetallation.

The thermolysis of arylcarbamates is the best method for conversion of I to metalloles, specially for the synthesis of remarkably dimerization-stable 1,1-R¹R²-3,4-dimethylmetalloles (≥ 80% yield). A one pot synthesis of these stable metalloles from the corresponding alcohol and phenyl isocyanate is proposed.

Unstable monomeric metalloles are stabilized by transition metal complexes or trapped by a (4 + 2) cycloaddition.     

Double stereoselective coordination of chiral N,S ligands: Synthesis,coordination chemistry and utilization in Pd‐catalyzed allylic alkylation

A series of chiral pentane‐2,4‐diyl‐based thioether‐amine ligands [ 4 and 5 ; (R,S)‐ and (S,S)‐R¹SCH(CH₃)CH₂CH(CH₃)NHR², respectively, where 4a R¹ = iPr, R² = Ph; 4b R¹ = tBu, R² = Ph; 4c R¹ = 1‐Ad, R² = Ph; 5a R¹ = iPr, R² = Ph; 5b R¹ = tBu, R² = Ph; 5c R¹ = 1‐Ad, R² = Ph; 5d R¹ = iPr, R² = 4‐MeOC₆H₄; 5e R¹ = iPr, R² = 4‐MeC₆H₄; 5f R¹ = iPr, R² = 3,5‐Me₂C₆H₃] with stereogenic S‐ and N‐donor atoms has been prepared starting from cyclic sulfates via optically pure γ‐aminoalcohol or 2,4‐dimethylazetidine intermediates. The synthesis of the novel diastereomerically related ligand sets 4 and 5 was accomplished starting from the same source of chirality. The modular ligand structure and the novel synthetic strategies developed for their synthesis allowed the easy modification of the ligands’ (i) S‐ and (ii) N‐substituents, as well as (iii) the relative stereochemistry within the ligand backbone. Six‐membered [Pd(N,S)Cl₂]‐type chelate complexes of the diastereomerically related ligands 4a and 5a were synthesized and characterized by X‐ray crystallography in the solid phase, by density functional theory calculations and in solution by NMR spectroscopy. The coordination of 5a resulted in the formation of a single chair conformation by the stereospecific locking of both stereolabile (N and S) donor atoms. In contrast, compound 4a forms rapidly equilibrating palladium species due to the fast inversion of the sulfur donor. Ligands with stereochemically fixed donor atoms provided robust and efficient catalytic systems that can be effectively applied in alkylene carbonates as green reaction media. Remarkably, the phosphine‐free catalysts are air‐stable, and at room temperature in the presence of moisture gave excellent ee’s (up to 93%) in asymmetric allylation processes thanks to the double stereoselective coordination.