Optical resolution of (±)-N-acylnorfenfluramine derivatives by preferential crystallization

Three stable and one unstable conglomerates (i. e. eutectic mixtures of D and L crystals) were found among nine synthesized (±)-N-acylnorfenfluramine derivatives. Optical resolution of the stable conglomerates could be achieved by preferential crystallization method only under nonisothermal conditions.     

Efficient resolution of (±)-pantolactone by inclusion crystallization with the use of chiral 1,1,2-triphenylethane-1,2-diol

Enantioselective formation of crystalline 1 : 1 host—guest complexes with (R)-or (S)-1,1,2-triphenylethane-1,2-diol as a host compound allows efficient preparative resolution of (±)-pantolactone. Optically active pantolactones (98%ee) were obtained in 65–67% yield. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1489–1490, August, 2000.     

Enzymatic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol and (±)-cis- and (±)-trans-2-aminoindan-1-ol

Pseudomonas cepacia lipase (PSL) efficiently catalyses the kinetic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol through the O-acylation reaction of the corresponding N-benzyloxycarbonyl derivative using vinyl acetate as the acyl donor. In a similar way, cis-N-Cbz-2-aminoindan-1-ol is resolved when isopropenyl acetate is used as the acylating agent. The enantioselectivity of the reaction was lower for (±)-trans-N-Cbz-2-aminoindan-1-ol due to the different steric requirements for the two conformers of this substrate.     

Mixtures obtained by reacting trans-(±)-1,2-diaminocyclohexane with acetylacetone in the presence of simple cobalt(II) salts

In the absence of a metal ion, racemic trans-1,2-diaminocyclohexane (trans-(±)DCH) reacts with acetylacetone (acacH) (1:2.5 mole ratio) to form the bisoxoenamine condensation product, boe (1). CoCl₂·6H₂O and Co(ClO₄)₂·6H₂O each react with trans-(±)DCH in air to give complexes containing the oxidised Co(III) ion, [Co((±)DCH)₃]³⁺, which does not subsequently react with added acacH to give a Schiff base complex. Mixtures of complexes are obtained from one-pot reactions involving trans-(±)DCH, a simple Co(II) salt and acacH (1:1:2.5 mole ratio). When CoCl₂·6H₂O is used, the mixed-ligand Co(II) complex [Co((±)DCH)Cl₂] (4) precipitates first and, after a period of weeks, the Co(II) complex (diazH)₂[CoCl₄] (5) (diazH⁺ is a diazepinium cation), the Co(II) complex [Co(boe)Cl₂]_n (6) and the Co(III) complex [Co(acac)₃] (7), co-crystallise from the mother liquor. Using Co(ClO₄)₂·6H₂O in the reaction with trans-(±)DCH and acacH also gives a mixture of products. Complexes 7, the Co(II) complex [Co₂(acac)₄(H₂O)₂][Co(acac)(H₂O)₄]ClO₄·EtOH (8) and the Co(III) complex [Co(acac)₂(±)DCH]ClO₄ (9) co-crystallise. Complexes 1, 5, 7, 8 and 9 were characterised using X-ray crystallography. The major difference between using CoCl₂·6H₂O and Co(ClO₄)₂·6H₂O in reactions involving (±)DCH and acacH is that no DCH/acacH condensation products are identified in the product mixtures when the perchlorate salt is employed.     

Enzymatic resolution of (±)-1-ferrocenylethylamine

(±)-1-Ferrocenylethylamine was resolved by a highly enantioselective acetylation catalyzed by Candida antarctica B lipase.     

Cu-catalyzed arylation of phosphinic amide facilitated by (±)-trans-cyclohexane-1,2-diamine

Cu-catalyzed cross coupling between phosphinic amides and aryl halides was accomplished for the first time by using(±)-trans- cyclohexane-1,2-diamine as the ligand.This reaction provided a novel approach for synthesizing arylated phosphinic amides.Both kinetic measurement and theoretical calculation indicated that phosphinic amides were much less reactive than amides by about 10 times in Cu-catalyzed cross coupling.     

Enantiomeric resolution of (±)-licarin A by high-performance liquid-chromatography using a chiral stationary phase

(±)-Licarin A (1), a neolignan obtained by the oxidative coupling reaction of isoeugenol, had in this study its enantiomers resolved. A novel, quick and efficient enantiomeric resolution of 1 was directly performed by chiral high-performance liquid chromatography (HPLC-PDA) protocol (CHIRALPACK^® AD column; 9:1 (v/v) n-hexane:2-propanol; 1.0 mL/min). This method provided a chromatogram profile with a well-resolved peak separation. After isolation of each enantiomer with ee > 99.9%, they were analysed in a polarimeter. Compound 2, which showed a retention time (t_r) of 12.13 min, was the (+)-enantiomer and compound 3 (t_r = 18.90 min) was the (−)-enantiomer.     

Synthesis,Structure and Norbornene Polymerization Activity of a Novel Palladium(Ⅱ) Complex with N,N-bis(2-benzoyl-3-oxobutane)-trans-1,2-diaminocyclohexane Ligand

The title complex N,N-bis(2-benzoyl-3-oxobutane)-trans-1,2-diaminocyclohexane-palladium(C28H28N2PdO4) has been synthesized by the reaction of N,N-bis(2-benzoyl-3-oxobutane)-trans-1,2-diamino-cyclohexane with PdCl2,and characterized by elemental analysis,IR spectrum,WAXD and TG.The spatial structures of the complex have been confirmed by single-crystal X-ray diffraction analysis.The compound crystallizes in the monoclinic system,space group C2/c with a = 29.763(6),b = 10.320(2),c = 18.921(4) ,β = 102.75(3)°,V = 5668(2) 3,C28H28N2PdO4·CH3OH,Mr = 594.97,Z = 8,Dc = 1.394 g/cm3,μ(MoKα) = 0.694 mm-1,F(000) = 2448,T = 293(2) K,R = 0.0572 and wR = 0.1347(I 2(I)).The compound was investigated for the catalytic behavior towards norbornene(NB) vinyl addition polymerization.And the palladium complex showed excellent catalytic activity up to 9.97×106 g of PNB(mol of Pd)-1 h-1 with high monomer conversion using methylaluminoxane(MAO) as a cocatalyst.     

Synthesis and spectral studies of Cu(II), Ni(II), Co(II) macrocyclic complexes by template reaction of (±)- trans -1,2-diaminocyclohexane,metal(II) nitrate and salicylaldehyde derivatives

Six new macrocyclic complexes were synthesized by template reactions of salicylaldehyde derivatives with (±)-trans-1,2-diaminocyclohexane and metal(II) nitrates. The metal to ligand ratio was 1 : 1. The Cu(II) complexes are proposed to be square planar and the Ni(II) and Co(II) complexes are proposed to be tetrahedral. The complexes are 1 : 2 electrolytes as shown by their molar conductivities (Λ_M) in DMF. The metal complexes are characterized by elemental analyses, FT-IR, UV–Vis, magnetic susceptibility measurements, molar conductivity measurements and mass spectra.     

An efficient large scale resolution of (±)-threo-methylphenidate hydrochloride (Ritalin® hydrochloride)

An efficient and large scale preparation of (2R,2′R)-(+)-threo-methylphenidate hydrochloride (3) by the resolution of (±)-threo-methylphenidate hydrochloride (1) salt with O,O′-dibenzoyl-d-(+)-tartaric acid in the presence of 4-methylmorpholine is described.     

Efficient kinetic resolution of (±)-4-methyl-Hajos–Parrish ketone by baker’s yeast reduction

Kinetic resolution of (±)-4-methyl-Hajos–Parrish ketone (±)-2a using baker’s yeast reduction was investigated. The reaction rate and enantiomeric purity depended on the concentration of substrate and yeast. Under concentrated conditions, (−)-2a and the alcohol (+)-3 were obtained in high enantiomeric excess.     

Enzymatic resolution of (±)-2-(Nβ-t-butoxycarbonyl-Nα-methylhydrazino)cycloalkanols

Racemates of cis- and trans-2-(N_β-t-butoxycarbonyl-N_α-methylhydrazino)cyclopentanols and -cyclohexanols 1–4 were resolved through lipase PS- or Novozym 435-catalysed asymmetric acylation of the secondary OH group at the (R)-stereogenic centre. High enantioselectivity (E >200) was observed when vinyl acetate or vinyl butyrate was used in diisopropyl ether, resulting in the enantiopure hydrazino esters 1a–4a and hydrazino alcohols 1b–4b. Methanolysis of the esters 1a–4a afforded the corresponding 2-hydrazinocycloalkanols 1c–4c (ee usually >95%).     

An Expeditious Total Synthesis of (±)-Sempervirol, (±)-Sugiol and (±)-Xanthopherol Methyl Ether by Acid-Catalyzed Cyclialkylation Route

An expeditious total synthesis of (±)-sempervirol (7) (±)-sugiol (8), and (±)-xanthopherol methyl ether (9) by extension of a simple general route is described. The stereochemical results of the cyclialkylation of 2-(2-p) and (2-m-isopropylphenylethyl)-1,3,3-trimethylcyclohexanols (1e) and (1f) follow the general pattern observed earlier.     

Facile Syntheses of (±)-Curcuphenol, (±)-Curcudiol, (±)-Curcuhydroquinone,and (±)-Curcuquinone

The syntheses of (±)-curcuphenol 1, (±)-curcudiol 2, (±)-curcuhydroquinone 3, and (±)-curcuquinone 4 have been achieved. The key steps involved in the syntheses were the Reformatsky reaction and hydrogenation reaction.