Synthesis and characterization of thiosemicarbazone derivatives of 2-chloro-4-hydroxy-benzaldehyde and their rhenium(I) complexes

N-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in chloroform gave the adducts [ReX(CO)₃(HL)] (1a X = Cl, R = H; 1a′ X = Br, R = H; 1b X = Cl, R = CH₃; 1b′ X = Br, R = CH₃; 1c X = Cl, R = Ph; 1c′ X = Br, R = Ph) in good yield. Complexes 1a′ and 1b’ were also obtained by the reaction of HL¹ and HL³ with [ReBr(CO)₅] in toluene.All the compounds have been characterized by elemental analysis, mass spectrometry (FAB), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³ and 1a·H₂O were also established by X-ray diffraction. In 1a, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms, forming a five-membered chelate ring, as well as three carbonyl carbon and chloride atoms. The resulting coordination polyhedron can be described as a distorted octahedron.The study of the crystals obtained by slow evaporation of methanol and DMSO solutions of the adducts 1a′ and 1b, respectively, showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆]·3H₂O (2a)·3H₂O and [Re₂(L²)₂(CO)₆]·(CH₃)₂SO (2b)·2(CH₃)₂SO. Amounts of these thiosemicarbazonate complexes [Re₂(L)₂(CO)₆] (2) were obtained by reaction of the corresponding free ligands with [ReCl(CO)₅] in dry toluene.In 2a·3H₂O and 2b·2(CH₃)₂SO the dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand. In both structures the rhenium coordination sphere is similar; the dimers are in the same diamond Re₂S₂ face.     

Synthesis,characterization and fluorescence properties of hexanuclear zinc(II) complexes

Two hexanuclear zinc(II) complexes, [Zn₆(L¹)₂(μ₂-OH)₂(μ₂-CH₃COO)₈] · CH₃CN (1 · CH₃CN) and [Zn₆(L²)₂(μ₂-OH)₂(μ₂-CH₃COO)₈] · 4CH₃CN (2 · 4CH₃CN), where HL¹ = 4-methyl-2,6-bis(cyclohexylmethyliminomethyl)-phenol and HL² = 4-methyl-2,6-bis(1-naphthalylmethyliminomethyl)-phenol, have been synthesized and characterized by elemental analysis, FT-IR and fluorescence spectroscopic methods, and by X-ray diffraction analysis. In the asymmetric unit of complex 1, two of the three zinc atoms have pentacoordinate geometries and the other is tetrahedrally coordinated, whereas the three distinct Zn atoms in complex 2 adopt three different coordination environments, namely distorted octahedral, trigonal bipyramidal and tetrahedral. The fluorescence properties of the ligands and complexes have been investigated.     

An expedient approach to ferrocenyl thioamides via Fischer carbenes

Oxidative demetalation of Fischer ferrocenyl ethoxy carbene complexes (1a–c, M = Cr, Mo, W) and new Fischer ferrocenyl R-amino carbene complexes [2–5 (a–c), 11–15 (a–c), and 21–22 (a–c); M = Cr, Mo, W; R = H, CH₃, C₂H₅, C₃H₇, (CH₂)₂OH, (CH₂)₃OH, (CH₂)₂(OMe)₂, (CH₂)₃N(Me)₂, CH₂CHCH₂, (CH₂)₂OSi(CH₃)₃, (CH₂)₃OSi(CH₃)₃] with elemental sulfur–NaBH₄ were carried out under mild conditions, obtaining O-ethyl ferrocenecarbothioate (6) and novel ferrocenyl thioamides (7–10 and 16–20) in excellent yields.     

Diiron chelate complexes relevant to the active site of the iron-only hydrogenase

A novel unsymmetrically disubstituted propanedithiolate compound [Fe₂(CO)₄(κ²-dmpe)(μ-pdt)] (1) (pdt = SCH₂CH₂CH₂S, dmpe = Me₂PCH₂CH₂PMe₂) was synthesized by treatment of [Fe₂(CO)₆(μ-pdt)] with dmpe in refluxing THF. Compound 1 was characterized by single-crystal X-ray diffraction analysis. Protonation of 1 with HBF₄·Et₂O in CH₂Cl₂ gave at room temperature the μ-hydrido derivative [Fe₂(CO)₄(κ²-dmpe)(μ-pdt)(μ-H)](BF₄)] (2). At low temperature, ¹H and ³¹P–{¹H} NMR monitoring revealed the formation of a terminal hydride intermediate 3. Comparison of these results with those of a VT NMR study of the protonation of symmetrical compounds [Fe₂(CO)₄L₂(μ-pdt)] [L = PMe₃, P(OMe)₃] suggests that in disubstituted bimetallic complexes [Fe₂(CO)₄L₂(μ-pdt)], dissymmetry of the complex is required to observe terminal hydride species. Attempts to extend the series of chelate compounds [Fe₂(CO)₄(κ²-L₂)(μ-pdt)] by using arphos (arphos = Ph₂AsCH₂CH₂PPh₂) were unsuccessful. Only mono- and disubstituted derivatives [Fe₂(CO)_6−n(Ph₂AsCH₂CH₂PPh₂)_n(μ-pdt)] (n = 1, 4a; n = 2, 4b), featuring dangling arphos, were isolated under the same reaction conditions of formation of 1. Compound 4b was structurally characterized.     

Novel Fe (III) heterochelates: Synthesis,structural features and fluorescence studies

Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H₂SB_n) and their Fe (III) heterochelates of the type [Fe(SB_n)(L)(H₂O)]·mH₂O [H₂SB_n = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = –CH₃, m = 4 (H₂SB₁); –C₆H₅, m = 2 (H₂SB₂); –CH₂–CH₃, m = 3 (H₂SB₃); –CH₂–CH₂–CH₃, m = 1.5 (H₂SB₄); –CH₂–C₆H₅, m = 1.5 (H₂SB₅) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (E_a), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported.     

Organoselenium(II) complexes containing organophosphorus ligands. Crystal and molecular structure of PhSeSP(S)Ph2, [2-{MeN(CH2CH2)2NCH2}C6H4]SeSP(S)R′2 (R′ = Ph,OPri) and [2-{O(CH2CH2)2NCH2}C6H4]SeSP(S)(OPri)2

Arylselenium(II) derivatives of dithiophosphorus ligands of type ArSeSP(S)R₂ [Ar = Ph, R = Ph (1), OPrⁱ (2); 2-[MeN(CH₂CH₂)₂NCH₂]C₆H₄, R = Ph (3), OPrⁱ (4); 2-[O(CH₂CH₂)₂NCH₂]C₆H₄, R = OPrⁱ (6)] were prepared by redistribution reactions between Ar₂Se₂ and [R₂P(S)S]₂. The derivative [2-{O(CH₂CH₂)₂NCH₂}C₆H₄]SeSP(S)Ph₂ (5) was obtained by the salt metathesis reaction between [2-{O(CH₂CH₂)₂NCH₂}C₆H₄]SeCl and NH₄S₂PPh₂. The compounds were investigated by multinuclear (¹H, ¹³C, ³¹P, ⁷⁷Se) NMR and infrared spectroscopy. The crystal and molecular structures of 1, 3, 4 and 6 were determined by single-crystal X-ray diffraction. In compounds 3, 4 and 6 the N(1) atom is intramolecularly coordinated to the selenium center, resulting in a T-shaped geometry (hypervalent 10-Se-3 species). The dithiophosphorus ligands act as anisobidentate in 1 and monodentate in 3, 4 and 6. Supramolecular architectures based on intermolecular S?H and N?H contacts between molecular units are formed in the hypervalent derivatives 3 and 4, while in the compounds 1 and 6 the molecules are associated into polymeric chains through either Se?S or O?H contacts, with no further inter-chain interactions.     

Preparation of (2,2-difluoroethenylidene)bis(tributylstannane) and arylation reaction: efficient approach to 1,1-diaryl-2,2-difluoroethenes

Reaction of 2,2-difluoro-1-tributylstannylethenyl p-toluenesulfonate (1) with bis(tributyltin) in the presence of 5 mol % Pd(PPh₃)₄ and 30 equiv LiBr in THF at reflux temperature for 7 h afforded (2,2-difluoroethenylidene)bis(tributylstannane) (2) in a 70% yield. Coupling reaction of 2 with aryl iodides in the presence of 5 mol % Pd(PPh₃)₄ and 5 mol % CuI in DMF at 80 °C for 3–4 h provided the coupled products 3 in 59–85% yields.     

Dinuclear ruthenium(I) complexes of the type [Ru2(CO)4L2] with carboxylate or 2-pyridonate ligands: Evaluation as catalysts for olefin cyclopropanation with diazoacetates

Dinuclear ruthenium(I,I) carboxylate complexes [Ru₂(CO)₄(μ-OOCR)₂]_n (R = CH₃ (1a), C₃H₇ (1b), H (1c), CF₃ (1d)) and 2-pyridonate complex [Ru₂(CO)₄(μ-2-pyridonate)₂]_n (3) catalyze efficiently the cyclopropanation of alkenes with methyl diazoacetate. High yields are obtained with terminal nucleophilic alkenes (styrene, ethyl vinyl ether, α-methylstyrene), medium yields with 1-hexene, cyclohexene, 4,5-dihydrofuran and 2-methyl-2-butene. The E-selectivity of the cyclopropanes obtained from the monosubstituted alkenes and the cycloalkenes decreases in the order 1b > 1a > 1d > 1c. The cyclopropanation of 2-methyl-2-butene is highly syn-selective. Several complexes of the type [Ru₂(CO)₄(μ-L¹)₂]₂ (4) and (5), [Ru₂(CO)₄(μ-L¹)₂L²] (L² = CH₃OH, PPh₃) (6)–(9) and [Ru₂(CO)₄(CH₃CN)₂(μ-L¹)₂] (10) and (11), where L¹ is a 6-chloro- or 6-bromo-2-pyridonate ligand, are also efficient catalysts. Compared with catalyst 3, a halogen substituent at the pyridonate ligand affects the diastereoselectivity of cyclopropanation only slightly.     

Ferromagnetic coupling of copper(II) and nickel(II) complexes with a cyclam-based paramagnetic host

Bis(NN–CH₂)-substituted dimethylcyclam (cyclamNN₂) was designed and synthesized as a paramagnetic host, where NN stands for 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide. We prepared transition-metal complexes [M(cyclamNN₂)](ClO₄)₂ (M = Cu (1), Ni (2)) and investigated their metal–radial exchange couplings. The copper ion in 1 is located at the center of the cyclam cavity and one radical arm is coordinated at an axial position. Compound 1 showed ferromagnetic coupling (2J/k_B = +44(3) K), which is ascribable to the NN–Cu coupling. Ferromagnetic coupling was also observed in 2, but the molecular structure was unknown at present. The Curie–Weiss analysis gave the Weiss temperature (θ) of +13.5(6) K for 2.     

Using pendant ferrocenyl group(s) as an intramolecular standard to probe the reduction of diiron hexacarbonyl model complexes for the sub-unit of [FeFe]-hydrogenase

The synthesis and characterisation of two diiron hexacarbonyl complexes [Fe₂(SXS)(CO)₆], 1 (SXS = ((^?SCH₂)₂C(CH₃)CH₂OCOFc, Fc = ferrocenyl group) and 2 (SXS = (^?SCH₂CH₂NHCOFc)₂), were described. By using intramolecularly integrated ferrocenyl group(s) in the complexes as an internal standard, the nature of two stepwise one-electron processes of the complexes coupled with a chemical reaction was clearly demonstrated. Examining how the reduction transformed into sole one-electron process with both increasing scanning rate under Ar/CO atmosphere and lowering temperature indicated conclusively that the reduction of both complexes couples to a chemical reaction which involves CO-loss.     

Seven-membered Pd(II) complexes containing symmetric phosphorus ylides: Synthesis,characterization and high catalytic activity toward Suzuki cross-coupling reactions

The reaction of 1,2-bis(diphenylphosphino)ethane (dppe) with various ketones in acetone produces the new phosphonium salts [RC(O)CH₂PPh₂(CH₂)₂PPh₂CH₂C(O)R]X₂ (R = 2-naphtyl, X = Br (1); R = 2,4-dichlorophenyl, X = Cl (2); R = 3-nitrophenyl, X = Br (3)). Further treatment with a base gives the symmetrical phosphorus ylides, RC(O)CHPPh₂(CH₂)₂PPh₂CHC(O)R (R = 2-naphtyl (4), 2,4-dichlorophenyl (5), 3-nitrophenyl (6)). These ligands react with Pd(II) chloride to form C,C-chelated complexes with the composition [RC(O)CHPPh₂(CH₂)₂PPh₂CHC(O)R]PdCl₂, where R = 2-naphtyl (7), 2,4-dichlorophenyl (8), 3-nitrophenyl (9). These compounds have been characterized by elemental analysis and spectroscopic methods and consist of seven-membered rings formed by the coordination of the ligands through the two ylidic carbon atoms to the metal center. The structure of compound 5 has been characterized crystallographically. The palladium complex 9 is employed in the Suzuki cross-coupling reaction between phenylboronic acid and several aryl halides. It was found to be a competent catalyst for a variety of substrates to afford the coupled products in high yields using DMF as a solvent. The biaryl products were obtained under aerobic conditions in short reaction times with a lower loading of the catalyst (0.001 mol%).     

Synthesis,structure and magnetic properties of {Mn5(OC(O)CH3)6(OC(O)C6H5)4}∞

The ligand exchange reaction between Mn(OC(O)CH₃)₂ and benzoic acid under solvothermal conditions in toluene at 110 °C yields colorless crystals of {Mn₅(OC(O)CH₃)₆(OC(O)C₆H₅)₄}_∞ (1). The asymmetric unit of this complex is Mn_2.5(OC(O)CH₃)₃(OC(O)C₆H₅)₂ with each of the three different Mn(II) atoms in 6-fold coordination and one of the benzoate ligands exhibiting the rare μ₃-symmetric bridging mode (O–Mn–O angle = 57°). The structure consists of edge-shared Mn₁₂ loops arranged in a honeycomb-like 2D sheet with the acetate ligands displaced slightly out of the plane. The sheets are spaced at 12 Å and linked into a 3D network via weak intersheet interactions. Magnetic susceptibility characterization of 1 indicates antiferromagnetic exchange with a Weiss constant of −165 K and a transition toward ferromagnetic exchange below 10 K corroborated with a finite imaginary component in the variable temperature susceptibility data.     

Luminescent coordination polymers with extended Au(I)–Ag(I) interactions supported by a pyridyl-substituted NHC ligand

Reaction of [Ag(CH₃impy)₂]PF₆, 1, with Au(tht)Cl produces the monometallic Au(I)-species [Au(CH₃impy)₂]PF₆, 2. Treatment of 2 with excess AgBF₄ in acetonitrile, benzonitrile or benzylnitrile produces the polymeric species {[AuAg(CH₃impy)₂(L)](BF₄)₂}_n, (L = CH₃CN,3; L = C₆H₅CN, 4; L = C₆H₅CH₂CN, 5) where the Au(I) centers remain bound to two carbene moieties while the Ag(I) centers are coordinated to two alternating pyridyl groups and a solvent molecule (L). Reaction of 2 with AgNO₃ in acetonitrile produces the zig-zag mixed-metal polymer {[AuAg(CH₃impy)₂(NO₃)]NO₃}_n, 6, that contains a coordinated nitrate ion in place of the coordinated solvent species. All of these polymeric materials are dynamic in solution and dissociate into their respective monometallic components. Compounds 2–6 are intensely luminescent in the solid-state and in frozen solution. All of these complexes were characterized by ¹H, ¹³C NMR, electronic absorption and emission spectroscopy and elemental analysis.     

New thioether–dithiolate complexes of Cp1Ir and some reactivity features

The reaction of [Cp1IrCl₂]₂ (Cp* = η⁵ ? C₅Me₅) with the tridentate 3-thiapentane-1,5-dithiolate ligand, S(CH₂CH₂S^?)₂ (tpdt), led to the formation of [Cp1Ir(η³ ? tpdt)] (1) in 81% isolated yield. Subsequent reactions of 1 with [Cp1IrCl₂]₂ in 2:1 and 1:1 molar equiv ratios resulted in the formation of [Cp1Ir(μ ? η²:η³ ? tpdt)Cp1IrCl][PF₆] (2) and [Cp1Irμ ? η²:η³ ? tpdt)Cp1IrCl][Cp1IrCl₃] (3) in 86 and 79% yields, respectively, based on 1, whereas the reactions of 1 with [(COD)IrCl]₂ (COD = 1,5-cyclooctadiene) in 2:1 and 1:1 molar equiv ratios resulted in the formation of the homo-bimetallic derivatives Cp1Ir(μ ? η¹:η³ ? tpdt)(COD)IrCl (4) (92% yield) and [Cp1Ir(μ ? η²:η³ ? tpdt)(COD)Ir] [(COD)IrCl₂] (5) (82% yield). Reactions between 1 and [(COD)RhCl]₂, yielded the hetero-bimetallic derivatives Cp1Ir(μ ? η¹:η³ ? tpdt)(COD)RhCl (6) and [Cp1Ir(μ ? η²:η³ ? tpdt)(COD)Rh][(COD)RhCl₂] (7), in 92 and 93% yields, respectively. The reaction of 1 with methyl iodide gave mono-methylated derivative [Cp1Ir(η³-C₄H₈S₃Me)]I (8) (93% yield). All these compounds have been comprehensively characterized.     

New thioether–dithiolate complexes of Cp1Ir and some reactivity features

The reaction of [Cp1IrCl₂]₂ (Cp* = η⁵ − C₅Me₅) with the tridentate 3-thiapentane-1,5-dithiolate ligand, S(CH₂CH₂S⁻)₂ (tpdt), led to the formation of [Cp1Ir(η³ − tpdt)] (1) in 81% isolated yield. Subsequent reactions of 1 with [Cp1IrCl₂]₂ in 2:1 and 1:1 molar equiv ratios resulted in the formation of [Cp1Ir(μ − η²:η³ − tpdt)Cp1IrCl][PF₆] (2) and [Cp1Irμ − η²:η³ − tpdt)Cp1IrCl][Cp1IrCl₃] (3) in 86 and 79% yields, respectively, based on 1, whereas the reactions of 1 with [(COD)IrCl]₂ (COD = 1,5-cyclooctadiene) in 2:1 and 1:1 molar equiv ratios resulted in the formation of the homo-bimetallic derivatives Cp1Ir(μ − η¹:η³ − tpdt)(COD)IrCl (4) (92% yield) and [Cp1Ir(μ − η²:η³ − tpdt)(COD)Ir] [(COD)IrCl₂] (5) (82% yield). Reactions between 1 and [(COD)RhCl]₂, yielded the hetero-bimetallic derivatives Cp1Ir(μ − η¹:η³ − tpdt)(COD)RhCl (6) and [Cp1Ir(μ − η²:η³ − tpdt)(COD)Rh][(COD)RhCl₂] (7), in 92 and 93% yields, respectively. The reaction of 1 with methyl iodide gave mono-methylated derivative [Cp1Ir(η³-C₄H₈S₃Me)]I (8) (93% yield). All these compounds have been comprehensively characterized.     

Mesoporous SBA-15-supported chiral catalysts: preparation,characterization and asymmetric catalysis

Two mesoporous silica-supported chiral Rh and Ru catalysts 5 and 6 with ordered two-dimensional hexagonal mesostructures were prepared by directly postgrafting organometallic complexes RhCl[(R)-MonoPhos(CH₂)₃Si(OMe)₃][(R,R)-DPEN] and RuCl₂[(R)-MonoPhos(CH₂)₃Si(OMe)₃][(R,R)-DPEN] (DPEN = 1,2-diphenylethylenediamine) on SBA-15. During the asymmetric hydrogenation of various aromatic ketones under 40 atm H₂, both catalysts exhibited high catalytic activities (more than 97% conversions) and moderate enantioselectivities (33–54% ee). Furthermore, the chiral Rh catalyst 5 could be easily recovered and used repetitively five times without significantly affecting its catalytic activity and enantioselectivity. A catalytic comparison of the mesoporous silica-supported chiral Rh catalyst 4 prepared by a postmodification method is also discussed.     

Syntheses,crystal structures and properties of dinuclear copper(I) complexes

Two dinuclear molecule-bridged Cu(I) complexes, (μ-bpym)[Cu(PPh₃)Cl]₂ (1), [(μ-bpym)(CuL)₂](ClO₄)₂·(CH₃CN)₂(H₂O) (2) (bpym = 2,2′-bipyrimidine, L = (R)-(+)-2,2′-bis(diphenylphospho)-1,1′-dinaphthalene) have been synthesized and characterized. The molecular structures of the two new dinuclear compounds exhibit bridging of two copper(I) centers by the symmetrically bis-chelating bpym ligand. Intriguingly, compound 1 features a remarkable “intramolecular organic sandwich” configuration where the central 2,2′-bipyrimidine bridging ligand interacts in π/π/π fashion with two phenyl rings from the coligands above and below the central plane, while chiral compound 2 exhibits second-order nonlinear optical effect and temperature-dependent luminescence. Upon decreasing the temperature from 298 to 10 K, compound 2 shows a red light emission.     

Stereospecific polymerization of propylene with group 4 ansa-fluorenylamidodimethyl complexes

Group 4 [η¹:η³-tert-butyl(dimethylfluorenylsilyl)amido]dimethyl complexes [t-BuNSiMe₂Flu]MMe₂ (M = Ti, 1; Zr, 2; Hf, 3) were synthesized in a one-pot synthesis starting from the ligand, MeLi and MCl₄ (M = Ti, Zr, Hf), respectively. The structures of these complexes were determined by X-ray crystallography and the results obtained revealed that the fluorenyl ligand coordinates to center metal in a η³-manner irrespective of center metal employed. Propylene polymerization was conducted at 0 or 20 °C in toluene by 1–3 combined with dried methylaluminoxane (MAO), which was prepared from the toluene solutions of MAO by removing free trialkylaluminiums, and HNMe₂PhB(C₆F₅)₄ in the presence of triisobutylaluminium. The 1–dried MAO system gave the polymer with syndiotactic triad (rr) of 63% at 0 °C, whereas 2 and 3 did not give any polymer in the same conditions. The 2–dried MAO system gave the polymer with the highest syndiotacticity (rr = 97%) at 20 °C, although the activity was low. The 3–dried MAO system did not give any polymer even at 20 °C. When HNMe₂PhB(C₆F₅)₄ was used in place of dried MAO at 20 °C, 1 gave almost atactic polymer, while 2 and 3 gave highly syndiotactic one (rr > 90%). These results indicate that the catalytic performance strongly depended on the center metal of the ansa-fluorenylamidodimethyl complexes as well as cocatalysts employed.     

Synthesis and crystal structure of a new water-soluble sulfur-containing palladacyclic diaqua complex

A new water-soluble sulfur-containing palladacyclic diaqua complex [(SC)Pd^II(H₂O)₂]₂(SO₄) {[1]₂(SO₄), SC = C₆H₄-2-(CH₂S^tBu)} was synthesized from a reaction of Ag₂SO₄ with a water-insoluble palladacyclic dichloro complex [(SC)Pd^II(μ-Cl)]₂ (2) in water. Water-solubility of [1]₂(SO₄) at pH 7 at 25 °C is 9.4 mg/mL. NH₄PF₆ was added to the solution of [1]₂(SO₄) in water to give [1](PF₆). The structures of [1](PF₆) and 2 were unequivocally determined by X-ray analysis.     

Candida antarctica lipase B-catalyzed ring opening of 4-arylalkyl-substituted β-lactams

The Lipolase-catalyzed ring opening of racemic 4-benzyl- 3 and 4-phenylethyl-2-azetidinone 4 was performed with 0.5 equiv of H₂O in diisopropyl ether at 45 °C. The resulting (S)-β-amino acid 5 or 6 (ee ⩾ 87%) and (R)-β-lactam 7 or 8 (ee >99%) enantiomers could easily be separated. The ring opening of enantiomeric β-lactams with 18% aqueous HCl afforded the corresponding enantiopure β-amino acid hydrochlorides 9 and 10 (ee >99%).