Simplified Approach to the Regiospecific Synthesis of Trichloromethylpyrazolines Using Microwave Irradiation

Twelve novel 3-alkyl[aryl]-1-carboxamides-5-trichloromethyl-5-hydroxy-4,5-dihydro-lH-pyrazole have been synthesized in good yields (72–90%) using environmentally benign microwave-induced techniques. The compounds were synthesized from the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alkyl[aryl]-2-ones [Cl₃CC(O)C(R²) = C(R¹)OR, where R = Me, Et; R¹ = H, Me, Et, Pr, i-Pr, i-Bu, t-Bu, Ph, Ph-4-NO₂, Ph-4-F, Ph-4-Cl, Ph-4-Br; and R² = H, Me] with semicarbazide hydrochloride in the presence of pyridine and using methanol/water (3:1 v/v) as the solvent. The advantages of using microwave irradiation, rather than a conventional method, were demonstrated.     

Substitution of Secondary Benzylic Phosphates with Diarylmethyl Anions

Substitution of diethyl and diphenyl benzylic phosphates, Alk-CH(Ar¹)OP(O)(OR)₂ (R = Et, Ph; Alk = Me, Et, i-Pr; Ar¹ = aryl), with the anions derived from Ar²CH₂ (Ph₂CH₂,9H-xanthene and fluorene) and n-BuLi at –15 °C was studied. For phosphates with Me as an Alk, diethyl phosphates produced Me-CH(Ar¹)CH(Ar²)₂ (Ar¹ = 4-halo-, 4-CN, 4-Me-, 2-Me, 2-Br-, 3-MeO-phenyl and 2-naphthyl). However, an unwanted substitution at the Et group competed with phosphates of Alk = Et- and i-Pr. Fortunately, the corresponding diphenyl phosphates cleanly underwent the desired substitution. Two enantioenriched phosphates, MeCH(Ph)OP(O)(OEt)₂ and EtCH(Ph)OP(O)(OPh)₂, proceeded with complete inversion of the stereochemistry.     

Enol ethers and acetals: acylation with dichloroacetyl,acetyl and benzoyl chloride in ionic liquid medium

Synthesis of 4-alkoxy-1,1-dichloro-3-alken-2-ones [CHCl₂C(O)C(R²)C(R¹)-OR, where R, R¹, R² = Et, H, H; Me, Me, H; Et, H, Me; Me, –(CH₂)₂–; Me, –(CH₂)₃–; Et, Et, H; Et, Bu, H; Et, i-Pr, H; Et, i-Bu, H; Me, Ph, H; Me, thien-2-yl, H] from acylation of enol ethers and acetals with dichloroacetyl chloride, in ionic liquid ([BMIM][BF₄] or [BMIM][PF₆]) is reported. The synthesis of alkenones [R³–C(O)C(R²)C(R¹)-OR], where R/R¹/R²/R³ = Et/H/H/Ph, t-Bu/H/H/Ph, Me/-(CH₂)₄/Ph, Me/-(CH₂)₄/Me] from the reaction of enol ethers with benzoyl chloride or acetyl chloride, in ionic liquid [BMIM][BF₄], is also reported. Last products are described for the first time.     

Baker's yeast reduction of α-methyleneketones

The bioreduction of α-methyleneketones, R¹C(O)C(CH₂)R² (R¹=Me, Et, Pr, iso-Bu, Ph, CH₂CH₂Ph; R²=Cl, Me, Et, n-Pr, iso-Pr, n-Bu, n-C₆H₁₃, Ph, CH₂Ph), was mediated by baker's yeast (Saccharomyces cerevisiae) to obtain the corresponding α-methylketones. The R¹ and R² groups had a significant influence on the rate and enantioselectivity of the reductions. The rate of CC bond reduction was higher than that of CO bond reduction. Only α-methyleneketones having R¹=Me yielded α-methylketones in high enantioselectivity with e.e.s of 88–99%.     

Homogeneous and Solid-Gas Hydrogenation of Alkynes in the Presence of the Clusters Fe3(CO)9(ε-RC2 R 1) {R=R 1=Ph, Et; R=Me, R 1=Ph}: Characterization of New Metallacyclic Derivatives

The clusters Fe₃(CO)₉(RC₂ R ¹) (R=R ¹=Ph, Et; R=Me, R ¹=Ph), complexes 1a, 1b, 1c, containing an alkyne bound in perpendicular fashion with respect to a cluster edge, catalyze the hydrogenation of some acetylenes either under homogeneous and solid–gas conditions. We hypothesize that cluster catalysis occurs and that the catalytic activity is related to the coordinating ability of the alkynic substrates. Competition between hydrogenation and formation of metallacyclic byproducts occurs. The new metallacyclic derivatives Fe₃(CO)₆(-CO)₂{(RC₂ R ¹)(R ²C₂ R ³)}, Fe₂(CO)₆{(RC₂ R ¹)(R ²C₂ R ³)} {R=R ¹=Et, R ²=R ³=H, Ph; R ²=Me, R ³=Et, Ph; R ²=H, R ³=Bu ^t . R=R ¹=Ph, R ²=Me, R ³=Et, Ph} (complexes 2, 3) were found both in the homogeneous reaction mixtures and after the solid–gas reactions. The formation of these products lowers the catalytic activity.     

Synthesis and characterization of cationic and zwitterionic allyl zirconium complexes derived from trimethylenemethane (TMM) cyclopentadienylzirconium acetamidinates

Protonation of the trimethylenemethane derivatives, Cp*Zr(σ²,π-C₄H₆)[N(R¹)C(Me)N(R²)] (1a: R¹=R²=i-Pr and 1b: R¹=Et, R²=t-Bu) (Cp*=η⁵-C₅Me₅), by [PhNMe₂H][B(C₆F₅)₄] in chlorobenzene at −10 °C provides the cationic methallyl complexes, Cp*Zr(η³-C₄H₇)[N(R¹)C(Me)N(R²)] (2a: R¹=R²=i-Pr and 2b: R¹=Et, R²=t-Bu), which are thermally robust in solution at elevated temperatures as determined by ¹H NMR spectroscopy. Addition of B(C₆F₅)₃ to 1a and 1b provides the zwitterionic allyl complexes, Cp*Zr{η³-CH₂C[CH₂B(C₆F₅)₃]CH₂}[N(R¹)C(Me)N(R²)] (3a: R¹=R²=i-Pr and 3b: R¹=Et, R²=t-Bu). The crystal structures of 2b and 3a have been determined. Neither the cationic complexes 2 or the zwitterionic complexes 3 are active initiators for the Ziegler-Natta polymerization of ethylene and α-olefins.     

Synthesis and reactivity of metal-containing monomers

Optically active mixed alkoxy orthotitanates with general formula Ti(OR¹)₂(OR²)(OR³) (R¹=Et, Buⁿ; R²=CH₂CH₂OCOC(Me)=CH₂; R³=menthyl, CH(Me)CH₂Me, CH(Ph)CH(NHMe)Me, CH(C₉H₆N)(C₉H₁₄N)) were obtained for the first time by transesterification. The Ti^IV monomers synthesized were characterized by elemental analysis, ozonolysis, and¹H and¹³C NMR and IR spectroscopy. Polymer products with optical activity were obtained by liquid phase radical copolymerization of Ti^IV-containing monomers. For Part 51, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1739–1743, September, 1999.     

Microwave-assisted synthesis of 5-trichloromethyl substituted 1-phenyl-1H-pyrazoles and 1,2-dimethylpyrazolium chlorides

A series of five 5-trichloromethyl-1-phenyl-1H-pyrazoles and six 5-trichloromethyl-1,2-dimethylpyrazolium chlorides have been synthesized in 80-98% yield by environmentally benign microwave induced techniques involving the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alken-2-ones [Cl₃C(O)C(R²)=C(R¹)OR, where R²=H, Me; R¹=H, alkyl, phenyl and R=Me, Et] with phenyl hydrazine and 1,2-dimethylhydrazine dihydrochloride, respectively, using toluene as solvent. The use of microwave and classical methods are comparable for making pyrazoles, but the formation of pyrazolium chlorides can be achieved in a significant shorter time, and in some cases better yield.     

Synthesis of Differently Substituted N- and P-Aminodiphosphinoamine PNPN-H Ligands

Abstract

On the basis of the known aminodiphosphinoamine ligand Ph₂PN(i-Pr)P(Ph) N(i-Pr)-H (3a), differently substituted aminodiphosphinoamine PNPN-H ligands (3) were prepared. By using different synthetic methods, the N-substituted ligands Ph₂PN (i-Pr)P(Ph)N(c-Hex)-H (3b), Ph₂PN(c-Hex)P(Ph)N(i-Pr)-H (3g), and Ph₂PN(i-Pr)P(Ph) N[(CH₂)₃Si(OEt)₃]-H (3c), in addition to the formerly described Ph₂PN(n-Hex)P (Ph)N (i-Pr)-H (3h), Ph₂PN(i-Pr)P(Ph)N(Et)-H (3d), Ph₂PN(i-Pr)P(Ph)N(Me)-H (3e), and Ph₂PN(c-Hex)P(Ph)N(c-Hex)-H (3f), were obtained. In addition, Ph₂PN(i-Pr)P(Me)N(i-Pr)-H (3i), (cyclopentyl)₂PN(i-Pr)P(Ph)N(i-Pr)-H (3j), (-O-CH₂-CH₂-O-)PN(i-Pr)P(Ph)N(i-Pr)-H (3k), and (1-Ad)₂PN(i-Pr)P(Ph)N(i-Pr)-H (3l) were prepared with different P-substitutions. All compounds were characterized and the molecular structures of the intermediates Ph₂PN(i-Pr)P(Ph)Cl (1a) and (cyclopentyl)₂PN(i-Pr)P(Ph)Cl (1e) and the ligand (1-Ad)₂PN(i-Pr)P(Ph)N(i-Pr)-H (3l) were investigated by single-crystal X-ray diffraction.

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.     

Cyclocondensation between fatty acid hydrazides and 1,1,1-trifluoro-4-alkoxy-3-alken-2-ones: Introducing a trifluoromethylated head onto fatty acid moieties

This paper reports the regioselective synthesis of new trifluoromethylated lipid derivatives, namely, 1-(5-hydroxy-5-trifluoromethyl-3-alkyl-4,5-dihydro-1H-pyrazol-1-yl)alkan-1-ones, through cyclocondensation reactions between a series of fatty hydrazides (palmitoyl, stearoyl, and oleoyl hydrazides) obtained from fatty acids from renewable resources (1,1,1-trifluoro-4-alkoxy-3-alken-2-ones [F₃CC(O)CH?C(R¹)OR, where R¹?=?H and R?Et; R¹?=?–(CH₂)₆CH₃, –(CH₂)₆CH₃, –(CH₂)₈CH₃, –(CH₂)₉CH₃, –(CH₂)₁₀CH₃, –(CH₂)₁₂CH₃, –(CH₂)₂Ph], and R?Me). Experimental observations showed that the lipophilic characteristic of 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles (5–7) prevent the acid catalyzed dehydration to aromatization of 1H-pyrazole ring, although in some cyclocondensations a proportion of the aromatic derivative 1-(5-trifluoromethyl-3-alkyl-1H-pyrazol-1-yl)alkan-1-one was obtained. All products were characterized using multinuclear (¹H, ¹³C, ¹⁹F) NMR spectroscopy.     

“Short-bite” ligands in cluster synthesis

The short-bite ligands CH₂(PR ₂)₂ or CH(PR ₂)₃ (R = Me, Ph),RN(PX ₂)₂ (R=H, Me, Et;X = F, OR (R= Me, Et, i-Pr, Ph), Ph),RE(CH₂ ER₂)₂ (E = P, As;R = Me, Ph ), Ph₂ P(2-C₅H₄N) and related species are particularly versatile for the synthesis of di- and polynuclear complexes which frequently possess metal-metal bonds. In addition to homometallic products, these ligands often permit the directed synthesis of heterometallic complexes. Selected aspects of the chemistry of these complexes are also reviewed.     

Formation and crystal structures of [(alkoxy)bis(pyridin-2-yl)methanolato-N,O,N]tin(IV) complexes

Reactions of bis(pyridin-2-yl)ketone with tin tetrahalides, SnX₄ (X = Cl or Br), or organotin trichlorides, R^′SnCl₃ (R^′ = Ph, Bu or CH₂CH₂CO₂Me), in ROH (R = Me or Et) readily produces RObis(pyridin-2-yl)methanolato)tin complexes, [5: RO(py)₂C(OSnX₃)] (5: R,X = Me,Cl; Et,Cl; Et,Br) or [6: MeO(py)₂C(OSnCl₂R^′)] (R^′ = Ph, Bu, CH₂CH₂CO₂Me). In addition, halide exchange reaction between SnI₄ and (5: R,X = Me,Cl) occurred to give (5: R,X = Me,I). The crystal structures of six tin(IV) derivatives indicated, in all cases, a monoanionic tridentate ligand, [RO(py)₂C(O⁻)-N,O,N], arranged in a fac manner about a distorted octahedral tin atom. The Sn–O and Sn–N bonds lengths do not show much variation amongst the six complexes despite the differences in the other ligands at tin.     

Palladium(II) compounds with planar chirality. X-Ray crystal structures of (+)-(R)-[{(η5-C5H4)–CHN–CH(Me)–C10H7}Fe(η5-C5H5)] and (+)-(Rp,R)-[Pd{[(Et–CC–Et)2(η5-C5H3)–CHN–CH(Me)–C10H7]Fe(η5-C5H5)}Cl]

A wide variety of planar chiral cyclopalladated compounds of general formulae [Pd{[(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl(L)] (with L=py-d₅ or PPh₃), [Pd{[(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}(acac)] or [Pd{[(R¹–CC–R²)₂(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl] (with R¹=R²=Et; R¹=Me, R²=Ph; R¹=H, R²=Ph; R¹=R²=Ph; R¹=R²=CO₂Me or R¹=CO₂Et, R²=Ph) are reported. The diastereomers {(R_p,R) and (S_p,R)} of these compounds have been isolated by either column chromatography or fractional crystallization. The free ligand (R)-(+)-[{(η⁵-C₅H₄)–CHN–CH(Me)–C₁₀H₇}Fe(η⁵–C₅H₅)] (1) and compound (+)-(R_p,R)-[Pd{[(Et–CC–Et)₂(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl] (7a) have also been characterized by X-ray diffraction. Electrochemical studies based on cyclic voltammetries of all the compounds are also reported.     

Preparation of highly enantiopure β-amino esters by Candida antarctica lipase A

The enantioselectivities for the reactions of aliphatic β-substituted β-amino esters [RCH(NH₂)CH₂CO₂Et with R=Me, Et, n-Pr, i-Pr, CHEt₂, cyclohexyl and Ph] with butyl butanoate in neat butyl butanoate and with 2,2,2-trifluoroethyl butanoate in diisopropyl ether were studied in the presence of Candida antarctica lipase A. Enantioselectivities ranging from good (E=70–100) to excellent (E>100) were commonly observed, allowing gram-scale resolution of the substrates.     

Reactions of σ-derivatives of trivalent titanium and vanadium with ketones

The interaction of Ph₃Ti with a number of ketones (acetone, 2-butanone, 3,3-dimethyl-2-butanone, benzophenone) was studied. The PhTi(OCR¹R²Ph)₂ complexes, where R¹=R²=Me (a), R¹=Me, R²=Et (b), R¹=Me, R²=t-Bu (c), and R¹=R²=Ph (d) were isolated in satisfactory yields. These compounds were characterized by ESR and IR spectroscopy and elemental analysis. Their thermal stability was determined by the DTA method. The reaction of Bn₃V with acetone gives V(OCMe₂Bn)₃. In analogy with titanium compounds, Bn₄V reacts with acetone at the ratio 12 to give Bn₂(OCMe₂Bn)₂.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1120–1122, June, 1994.     

EINIGE NEUE THIOPHOSPHINSÄUREAMIDE R2P(S)NHR': SYNTHESE UND KERNRESONANZSPEKTROSKOPISCHE UNTERSUCHUNGEN

Abstract

P.P-Dialkylthiophosphinsäureamide R₂P(S)NHR' (R=Me, 'Pr, 'Bu; R'=Me, Et, ⁱPr. ^cHex. ^tBu. Ph. etc.) wurden erhalten durch Umsetzung von R₂PNHR' mit Schwefel oder durch Reaktion von Me₂P(S)CI mit primaren Aminen. Ihre ³¹P- und ¹³C-NMR-Spektren werden diskutiert. Insbesondere die Di-t-butylthiophosphinsäureamide sind auszilg;ergewöhnlich stabil gegen Hydrolyse und Luftsauerstoff. P,P-Dialkylthiophosphinic acid amides R₂P(S)NHR' (R=Me. ⁱPr. ^tBu; R'=Me, Et, ⁱPr, ^cHex. ^tBu, Ph. etc.) have been obtained by reaction of the corresponding aminophosphines with sulfur or by reaction of dimethylthiophosphorylhalides with primary amines. Their ³¹P- and ¹³C-NMR spectra are discussed. The di-t-butylthiophosphinic compounds proved to be remarkably stable against moisture and oxygen.     

Synthesis and characterization of aluminum(III) and tin(II) complexes supported by diiminophosphinate ligands and their application in ring‐opening polymerization catalysis of ε‐caprolactone

A series of Al(III) and Sn(II) diiminophosphinate complexes have been synthesized. Reaction of Ph(ArCH₂)P(?NBu^t)NHBu^t (Ar = Ph, 3 ; Ar = 8‐quinolyl, 4 ) with AlR₃ (R = Me, Et) gave aluminum complexes [R₂Al{(NBu^t)₂P(Ph)(CH₂Ar)}] (R = Me, Ar = Ph, 5 ; R = Me, Ar = 8‐quinolyl, 6 ; R = Et, Ar = Ph, 7 ; R = Et, Ar = quinolyl, 8 ). Lithiated 3 and 4 were treated with SnCl₂ to afford tin(II) complexes [ClSn{(NBu^t)₂P(Ph)(CH₂Ar)}] (Ar = Ph, 9 ; Ar = 8‐quinolyl, 10 ). Complex 9 was converted to [(Me₃Si)₂NSn{(NBu^t)₂P(Ph)(CH₂Ph)}] ( 11 ) by treatment with LiN(SiMe₃)₂. Complex 11 was also obtained by reaction of 3 with [Sn{N(SiMe₃)₂}₂]. Complex 9 reacted with [LiOC₆H₄Bu^t‐4] to yield [4‐Bu^tC₆H₄OSn{(NBu^t)₂P(Ph)(CH₂Ph)}] ( 12 ). Compounds 3–12 were characterized by NMR spectroscopy and elemental analysis. The structures of complexes 6 , 10 , and 11 were further characterized by single crystal X‐ray diffraction techniques. The catalytic activity of complexes 5–8 , 11 , and 12 toward the ring‐opening polymerization of ε‐caprolactone (CL) was studied. In the presence of BzOH, the complexes catalyzed the ring‐opening polymerization of ε‐CL in the activity order of 5 > 7 ≈ 8 > 6 ? 11 > 12 , giving polymers with narrow molecular weight distributions. The kinetic studies showed a first‐order dependency on the monomer concentration in each case. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4621–4631, 2006     

Acyl Iodides in Organic Synthesis: I. Reactions with Alcohols

Reaction of acyl iodides RC(O)I (R = Me, Ph) with alcohols R'OH (R' = Me, Et, i-Pr, t-Bu, CH₂ = CHCH₂, HCCCH₂) provides in the corresponding organyl iodides R'I. Unlike that 2-chloroethanol and phenol (R' = CH₂CH₂Cl, Ph) react with RC(O)I in the same way as with acyl chlorides yielding esters RCO₂R'. This reaction path occurs partially also with methanol and ethanol.     

Reactions of Diazo Compounds with Alkenes Catalysed by [RuCl(cod)(Cp)]: Effect of the Substituents in the Formation of Cyclopropanation or Metathesis Products

The reaction of diazo compounds with alkenes catalysed by complex [RuCl(cod)(Cp)] (cod=1,5‐cyclooctadiene, Cp=cyclopentadienyl) has been studied. The catalytic cycle involves in the first step the decomposition of the diazo derivative to afford the reactive [RuCl(Cp){?C(R¹)R²}] intermediate and a mechanism is proposed for this step based on a kinetic study of the simple coupling reaction of ethyl diazoacetate. The evolution of the Ru–carbene intermediate in the presence of alkenes depends on the nature of the substituents at both the diazo N₂?C(R¹)R² (R¹, R²=Ph, H; Ph, CO₂Me; Ph, Ph; C(R¹)R²=fluorene) and the olefin substrates R³(H)C?C(H)R⁴ (R³, R⁴=CO₂Et, CO₂Et; Ph, Ph; Ph, Me; Ph, H; Me, Br; Me, CN; Ph, CN; H, CN; CN, CN). A remarkable reactivity of the complex was recorded, especially towards unstable aryldiazo compounds and electron‐poor olefins. The results obtained indicate that either cyclopropanation or metathesis products can be formed: the first products are favoured by the presence of a cyano substituent at the double bond and the second ones by a phenyl.     

Cationic tris(pyrazolyl)borate bipyrimidine complexes

The cationic complexes, [Tp^RNi(bpym)]⁺ {Tp^R = tris(3,5-diphenylpyrazolyl)borate, R = Ph₂ 1; tris(3-phenyl-5-methylpyrazolyl)borate, R = Ph,Me 2} were synthesized by reacting [Tp^RNiBr] (R = Ph₂; Ph,Me) with bipyrimidine followed by subsequent addition of KPF₆ in CH₂Cl₂. The green solids have been characterized by IR, UV–Vis and ¹H NMR spectroscopy. Crystallographic studies of [Tp^Ph,MeNi(bpym)]PF₆ reveal a five-coordinate square pyramidal nickel centre with a κ³-coordinated Tp^Ph,Me ligand and a chelating bipyrimidine ligand. Cyclic voltammetric studies show irreversible reduction with the degree of reversibility dependent on the type of Tp^R ligand.