Emission of 2-phenylethanol from its β-d-glucopyranoside and the biogenesis of these compounds from [H8] l-phenylalanine in rose flowers

The hydrolysis of 2-phenylethyl β-d-glucopyranoside (3) was found to be partially inhibited by feeding with 2-phenyl-N-glucosyl-acetamidiumbromide (8), a β-glucosidase inhibitor, resulting in a decrease in the diurnal emission of 2-phenylethanol (2) from Rosa damascena Mill. flowers. Detection of [1,1,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2′,3′,4′,5′,6′-²H₇]-2 from R. ‘Hoh-Jun’ flowers fed with [1,1,2,2′,3′,4′,5′,6′-²H₈]-3 suggested that β-glucosidase, alcohol dehydrogenase, and reductase might be involved in scent emission. Comprehensive GC-SIM analyses revealed that [1,2,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2,2′,3′,4′,5′,6′-²H₈]-3 must be biosynthesized from [1,2,2,2′,3′,4′,5′6′-²H₈] l-phenylalanine ([²H₈]-1) with a retention of the deuterium atom at α-position of [²H₈]-1.     

The first synthesis of N,O-protected β-isoserines bearing two adjacent quaternary stereogenic centers and their corresponding β-lactams

The reaction of chiral (2S)-enolates of dioxolan-4-ones, derived from lactic and mandelic acids, with (S_R)-tert-butyl sulfinyl ketimines, derived from butan-2-one, pentan-2-one, and decan-2-one, afforded conformationally restrained β^2,2,3,3-isoserines bearing two adjacent quaternary stereogenic centers in the form of N-sulfinyl protected 1′-amino-dioxolan-4-ones. The selective acid-induced removal of the sulfinyl protecting group provided the corresponding 1′-aminodioxolanones, whose base-induced cyclization afforded the corresponding chiral tetra-substituted 3-hydroxy-β-lactams. The synthesis of a dipeptide by reaction coupling between the 1′-aminodioxolanone (2S,5R,1′R)-19 and N,N-dimethylglycine was successfully achieved.     

Novel fluoro-substituted benzo- and benzothieno fused pyrano[2,3-c]pyrazol-4(1H)-ones

A straightforward, two-step synthesis of fluoro substituted chromeno[2,3-c]pyrazol- and [1]benzothieno[2′,3′:5,6]pyrano[2,3-c]pyrazol-4(1H)-ones, respectively, is presented. Hence, treatment of 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with fluoro substituted 2-fluorobenzoyl chlorides or 3-chloro-6-fluoro-1-benzothiophene-2-carbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane gave the corresponding 4-aroylpyrazol-5-ols, which were cyclized into the fused ring systems. 5-Fluorochromeno[2,3-c]pyrazol-4(1H)-one was obtained upon treatment of the 1-(4-methoxybenzyl) protected congener with trifluoroacetic acid. Treatment of 5-fluorochromeno[2,3-c]pyrazol-4(1H)-ones with methylhydrazine afforded novel tetracyclic ring systems such as 2-methyl-7-phenyl-2,7-dihydropyrazolo[4′,3′:5,6]pyrano[4,3,2-cd]indazole. Detailed NMR spectroscopic investigations (¹H, ¹³C, ¹⁵N, ¹⁹F) with the obtained compounds were undertaken.     

Structural study of oxalamide compounds: H, C, and DFT calculations

The conformational properties of some N-alkyl, N,N′-dialky, and tetraalkyloxalamides have been investigated, in vacuo and in solvent using DFT methods at the B3LYP/6-31G^∗∗ computational level. Special emphasis has been given on oxalamides with substituents of the type -CH₂CH₂OH. In oxalamides with the N-H group (N-alkyl and N,N′-dialky), the most stable conformations are those in which the oxalamide moiety adopts a planar s-trans arrangement and the amide bonds are trans. A different situation appears in the case of tetraalkyloxalamides, in which the oxalamide moiety always adopts a skewed arrangement and there are conformations with similar energy. A careful study of ¹³C and ¹H NMR spectra together with theoretical calculations (GIAO method) allowed the assignment of the signals of these conformers. The presence of the -CH₂CH₂OH chain produces numerous rotamers. The most stable rotamers, in vacuo, are those with strong intramolecular hydrogen bonds, however in solvent, hydrogen bonds are not crucial to establish the most stable specie and depend on the solvent used.     

Mononuclear hydridocarbonyl ruthenium complexes incorporating N2O2 bis-chelating ligands

The reactions of [RuH(CO)Cl(PPh₃)₃] with N,N^′-bis(salicylidine)-hydrazine (H₂bsh) and N,N^′-bis(salicylidine)-p-phenylene diammine (H₂bsp) in presence of KOH in methanol led in the formation of neutral mononuclear complexes with the formulations [RuH(CO)(PPh₃)₂(L)] (LHbsh or Hbsp). These present the first examples where the ligands H₂bsh or H₂bsp provide only two of its available donor sites for interaction with the metal centre. The complexes have been characterized by elemental analyses, FAB-MS, IR, ¹H, ¹³C, ³¹P NMR and electronic spectral studies. Molecular structure of the representative complex [RuH(CO)(PPh₃)₂(Hbsh)] have been determined by single crystal X-ray analysis.     

Cobalt complexes of a selenium diimide and a tellurium diimide dimer

[CoCl₂{N,N′-Te₂(N^tBu)₄}] (1) was obtained in good yields by the reaction of equimolar amounts of (^tBu)NTe(μ-N^tBu)₂TeN(^tBu) and CoCl₂ in toluene under an argon atmosphere. The crystal structure of 1·CH₂Cl₂ showed that the dimeric tellurium diimide ligand is N,N′-chelated to cobalt. The related reaction of Se(N^tBu)₂ and CoCl₂ affords a green product tentatively identified as a 1:1 adduct [CoCl₂{N,N′-Se(N^tBu)₂}] (CHN analysis). However, recrystallization from thf produces the ion-separated complex [Co₂(μ-Cl)₃{N,N′-Se(N^tBu)₂}₂(thf)₂][CoCl₃{NH₂(^tBu)}]·1½thf (2·1½thf), in which the monomeric selenium diimide ligand is N,N′-chelated to cobalt in the cation. A pathway for the formation of 2 from [CoCl₂{N,N′-Se(N^tBu)₂}] in thf is proposed.     

Synthesis, characterisation and X-ray structures of diorganotin(IV) and iron(III) complexes of dianionic terdentate Schiff base ligands

Diorganotin(IV) complexes, [SnR₂L] (1)-(4), (R = Me, Ph), of the terdentate Schiff bases N-[(2-pyrroyl)methylidene]-N′-tosylbenzene-1,2-diamine (H₂L¹) and N-[(2-hydroxyphenyl)metylidene]-N′-tosylbenzene-1,2-diamine (H₂L²) have been synthesised. The complexes were obtained by addition of the appropriate ligand to a methanol suspension of the corresponding diorganotin(IV) dichloride in the presence of triethylamine. However, the reaction between the precursor [η⁵-C₅H₅Fe(CO)₂]₂SnCl₂ and the Schiff bases in the presence of triethylamine gave (5) and (6), respectively. The crystal structures of the ligands and complexes have been studied by X-ray diffraction. The structure of [SnR₂L] complexes shows the tin to be five-coordinate in a distorted square pyramidal environment with the dianionic ligand acting in a terdentate manner. In 5 and 6, the iron atom is in a slightly distorted octahedral environment and is meridionally coordinated by two ligands. Spectroscopic data for the ligands and complexes (IR, ¹H, ¹³C and ¹¹⁹Sn NMR and mass spectra) are discussed and related to the structural information.     

N,N-polymethylene-bisadenine complexes with d metal ions

The reaction of N⁹,N^9′-(tri or tetramethylene)-bisadenines (Ade₂C_x; x = 3 or 4) in HCl 2 M at 50 °C with MCl₂ · 2H₂O [M = Zn(II), Cd(II)] yields outer sphere compounds like the previously described [(H-Ade)₂C₃][ZnCl₄] · H₂O (3) and [(H-Ade)₂C₃]₂[Cd₂Cl₈(H₂O)₂] · 4H₂O (4) for Ade₂C₃ and the new {[(H-Ade)₂C₄][Cd₂Cl₆(H₂O)₂] · 2H₂O}_n (5) for Ade₂C₄. On the other hand, only in case of Zn(II) complexes by changing [HCl] to 0.1 M, the inner sphere compounds [H-(Ade)₂C₃(ZnCl₃)] (6) and [H-(Ade)₂C₄(ZnCl₃)] · 1.5H₂O (7) are obtained. X-ray diffraction study of compound 6, which represents the first inner sphere complex with a N⁹,N^9′-bisadenine, shows a zwitterionic form with one adenine ring protonated at N(1) while the other ring is coordinated via N(7) to a ZnCl₃ moiety as in other alkyl-adenine derivatives. In addition, with Ade₂C₄, is also possible to obtain another inner sphere complex: [(H-Ade)₂C₄(ZnCl₃)₂] · 3H₂O (8).     

Synthesis and structure of diamine bis(phenolate) complexes containing the Ti(OEt)–O–Ti(OEt) function

Reaction of diamine-bis(phenol) ligands containing a mixture of N-methyl and N,N′-dimethyl-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine, H₂L¹ and H₂L³, with [Ti(OCHMe₂)₄ in absolute ethanol under reflux without exclusion of air and moisture gives [(L¹)Ti (OEt–O–Ti(OEt)(L¹)] (1). [(L³)Ti(OEt)–O–Ti(OEt)(L³)] (2) forms when the remaining solution containing [(L³)Ti(OEt)₂] (3) (characterised by X-ray crystallography) is hydrolysed with H₂O. For the N-methyl and N,N′-dimethyl ligand mixture H₂L² and H₂L⁴, which contain tert-butyl groups on the ortho-positions of the aryl rings, [(L²)Ti(OEt)–O–Ti(OEt)(L²)] (4) forms much more slowly and [(L⁴)Ti(OEt)₂] (5) does not hydrolyse when H₂O is added. When the N-protonated ligand N,N-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine, H₂L⁵, is used, rapid hydrolysis to two isomers of [(L⁵)Ti(OEt–O–Ti(OEt)(L⁵)] (6) occurs without addition of water. For N,N-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine, H₂L⁶, hydrolysis to [(L⁶)Ti(OEt)–O–Ti(OEt)(L⁶)] (7) occurs slowly when H₂O is added. For pendant NMe₂ ligand N,N-dimethyl-N′,N′-bis(2-hydroxy-3-methyl-5-tert-butylbenzyl)ethylenediamine, H₂L⁷, the hydrolysis reaction readily gives [(L⁷)Ti(OEt)–O–Ti(OEt)(L⁷)] (8) for which an X-ray crystal structure was obtained. The ortho-tert-butyl ligand derivative H₂L⁸ formed a complex analysing as [(L⁸)Ti(OEt)–O–Ti(OEt)(L⁸)] (9) which could not be studied further due to insolubility. Pendant pyridine ligand N-(2-pyridylmethyl)-N,N-bis(2′-hydroxy-3′-methyl-5′-tert-butylbenzyl)amine, H₂L⁹, apparently forms isomers of [(L⁹)Ti(OEt)–O–Ti(OEt)(L⁹)] and possibly [{(L⁹)Ti(O)}₂] from [(L⁹)Ti(OEt)₂] (10). The ortho-tert-butyl ligand derivative H₂L¹⁰ formed [(L¹⁰)Ti(OEt)–O–Ti(OEt)(L¹⁰)] (11) for which an X-ray crystal structure was obtained.     

Uranyl(VI) complexes of [O,N,O,N′]-type diaminobis(phenolate) ligands: Syntheses,structures and extraction studies

The syntheses and crystal structures of four new uranyl complexes with [O,N,O,N′]-type ligands are described. The reaction between uranyl nitrate hexahydrate and the phenolic ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N′,N′-dimethylethylenediamine)], H₂L1 in a 1:2 molar ratio (M to L), yields a uranyl complex with the formula [UO₂(HL1)(NO₃)] · CH₃CN (1). In the presence of a base (triethylamine, one mole per ligand mole) with the same molar ratio, the uranyl complex [UO₂(HL1)₂] (2) is formed. The reaction between uranyl nitrate hexahydrate and the ligand [(N,N-bis(2-hydroxy-3,5-di-t-butylbenzyl)-N′,N′-dimethylethylenediamine)], H₂L2, yields a uranyl complex with the formula [UO₂(HL2)(NO₃)] · 2CH₃CN (3) and the ligand [N-(2-pyridylmethyl)-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)amine], H₂L3, in the presence of a base yields a uranyl complex with the formula [UO₂(HL3)₂] · 2CH₃CN (4). The molecular structures of 1–4 were verified by X-ray crystallography. The complexes 1–4 are zwitter ions with a neutral net charge. Compounds 1 and 3 are rare neutral mononuclear [UO₂(HLn)(NO₃)] complexes with the nitrate bonded in η²-fashion to the uranyl ion. Furthermore, the ability of the ligands H₂L1–H₂L4 to extract the uranyl ion from water to dichloromethane, and the selectivity of extraction with ligands H₂L1, H₃L5 (N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-3-amino-1-propanol), H₂L6 · HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane · HCl) and H₃L7 · HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-6-amino-1-hexanol · HCl) under varied chemical conditions were studied. As a result, the most efficient and selective ligand for uranyl ion extraction proved to be H₃L7 · HCl.     

H-quadrupolar coupling-based analysis of stereochemical and regiochemical memory in the Pd-catalysed allylic alkylation of iso-cinnamyl type substrates employing the chiral monophosphine ligands ‘MOP’ and ‘MAP’

The reaction of iso-cinnamyl acetate with NaC(Me)(CO₂Me)₂, catalysed by Pd-‘MOP’ (MOP=2-methoxy-2′-diphenylphosphino-1,1′-binaphthalene) is known to proceed with a regiochemical memory effect that results in the predominant generation of the branched alkylation product. The analogous reaction employing ‘MAP’ as ligand (MAP=2-N,N-dimethylamino-2′-diphenylphosphino-1,1′-binaphthalene) proceeds with ‘normal’ regioselectivity to generate predominantly the linear isomer of product. A ²H-NMR based analysis, employing quadrupolar coupling in a chiral liquid crystal matrix, has been developed to facilitate the simultaneous study of the regiochemical and stereochemical outcome of the reaction of both enantiomers of iso-cinnamyl ester substrates in ²H-labelled but racemic samples. The analysis allows the comparison of relative rates of two competing isomerisation processes occurring in the π-allyl intermediates in the Pd-catalysed reaction, one of which facilitates asymmetric induction, the other resulting in loss of regiochemical memory. It is demonstrated that the two processes are partially coupled and that this then limits the attainment of high global enantiomeric excess in the branched product to reactions that proceed with low regiochemical retention. A key factor for the observation of high regiochemical memory is found to be the nucleophilicity of the malonate anion and the electrophilicity of the Pd-π-allyl intermediate with reduction in the reactivity of either partner resulting in the onset of substantial loss of memory.     

Synthesis,structure and thermal properties of polynuclear complexes with a new multidentate ligand, N,N′-bis(5-ethyl-1,3,4-thiadiazol-2-yl)-2,6-pyridinedicarboxamide

Based on N,N′-bis(5-ethyl-1,3,4-thiadiazol-2-yl)-2,6-pyridinedicarboxamide (H₂L) and inorganic Zn^II and Cd^II salts, three polynuclear complexes [Zn₆(μ₄-O)₂(L)₄] (1), [Zn₃(μ₃-O)₂(L)₂(H₂L)] (2) and [Cd₅(μ₃-O)₂(L)₃(H₂L)(CH₃OH)(DMF)] (3) have been prepared and their crystal structures have been determined by single-crystal X-ray analysis. The thermal behaviors of these complexes in nitrogen and the thermal decomposition kinetics of complex 2 in the temperature range 350–540 °C have been studied, and kinetic parameters were also obtained. Kinetic results show that the decomposition of complex 2 is double-step reaction: a 1st-order reaction (F1) is followed by an nth-order reaction (Fn).     

Reactivity of M(en)Cl2 (M = Pd/Pt,en = 1,2-diaminoethane) with N,N′-bis(salicylidene)-p-phenylenediamine: Binding with hexafluorobenzene

Schiff base N,N′-bis(salicylidene)-p-phenylenediamine (LH₂) complexed with Pt(en)Cl₂ and Pd(en)Cl₂ provided [Pt(en)L]₂ · 4PF₆ (1) and Pd(Salen) (2) (Salen = N,N′-bis(salicylidene)-ethylenediamine), respectively, which were characterized by their elemental analysis, spectroscopic data and X-ray data. A solid complex obtained by the reaction of hexafluorobenzene (hfb) with the representative complex 1 has been isolated and characterized as 3 (1 · hfb) using UV–Vis, NMR (¹H, ¹³C and ¹⁹F) data. A solid complex of hfb with a reported Zn-cyclophane 4 has also been prepared and characterized 5 (4 · hfb) for comparison with complex 3. The association of hfb with 1 and 4 has also been monitored using UV–Vis and luminescence data.     

Acyclic tertiary diamines and 1,4,7,10-tetraazacyclododecane with fluorine-containing β-diketones: Leading to low melting ionic adducts

N,N,N′,N′-Tetramethylmethanediamine (1a), N,N,N′,N′-tetramethylethanediamine (1b), N,N,N′,N′-tetramethyl-1,3-propanediamine (1c), and N,N,N′,N′-tetramethyl-1,6-hexanediamine (1d) were reacted at 25 °C with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (2a), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione (2b), 2-thenoyltrifluoroacetone (2c), and 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (2d) to form the ionic adducts 3-18. 1,4,7,10-Tetraazacyclododecane (1e) reacted at 25 °C with β-diketones (2a-d) and 1,1,1-trifluoro-2,4-pentanedione (2e) to give ionic solids 19-23 in good yields. Some of the products are liquid at 25 °C and are thermally stable over long liquid ranges as determined by thermal gravimetric analyses. Single-crystal X-ray structure determinations show that compounds 9 and 21 crystallize in the monoclinic space groups P2(1)/c and P2(1)/n, respectively. All the new compounds were characterized by ¹H, ¹⁹F and ¹³C NMR, electrospray MS and/or elemental analyses.     

Synthesis and properties of novel 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-triones: methodology for synthesizing cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates

Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac₂O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The ¹³C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG^‡) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03 kcal mol⁻¹ by the variable temperature ¹H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF₄⁻ and 12a-c·BF₄⁻) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF₄⁻) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)-pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF₄/Ac₂O afforded two kinds of novel products 11a-c·BF₄⁻ and 12a,c·BF₄⁻ in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF₄⁻ and 12a-c·BF₄⁻ observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF₄⁻ and 12a-c·BF₄⁻ were studied, and structural characterization of 11c·BF₄⁻ based on the X-ray crystal analysis and MO calculation was also performed.     

Convenient synthesis of N-isobutyryl-2′-O-methyl guanosine by efficient alkylation of O-trimethylsilylethyl-3′,5′-di-tert-butylsilanediyl guanosine

We present a novel route for the synthesis of N²-isobutyryl-2′-O-methyl guanosine, introducing 3′,5′-di-tert-butylsilyl and O⁶-trimethylsilylethyl groups as efficient protections during the 2′-O-methylation step with NaH/CH₃I. These protections were then removed simultaneously in a single step with TBAF. The eight-step synthesis is easy to perform, employing convenient commercially available reagents; crude mixtures are of satisfying purity, so only three chromatography purifications were required. Title compound was obtained in 25% overall yield from guanosine.     

Rapid synthesis of optically active poly(amide-imide)s by direct polycondensation of aromatic dicarboxylic acid with aromatic diamines

4,4^′-(Hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine-p-amidobenzoic acid) (2) was prepared from the reaction of 4,4^′-(hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine) diacid chloride with p-aminobenzoic acid. The direct polycondensation reaction of monomer (2) with p-phenylenediamine (2a), 4,4^′-diaminodiphenylsulfone (2b), 2,4-diaminotoluene (2c), 2,6-diaminopyridine (2d), m-phenylene diamine (2e), benzidine (2f), 4,4^′-diaminodiphenylether (2g) and 4,4^′-diaminodiphenyl methane (2h) was carried out in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone, pyridine, and calcium chloride. The homogeneous mixture was heated at 220 °C for 1 min under nitrogen. The resulting poly(amide-imide)s (PAIs) having inherent viscosities 0.27-0.78 dl/g were obtained in high yield and are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses and specific rotation. Some structural characterization and physical properties of this new optically active PAIs are reported.     

Mercury(II) complex of inverted N-methylated porphyrin: HgPh(2-NCH3NCTPP)

The reaction of PhHgOAc with 2-NCH₃NCTPPH (2) gave a mercury(II) complex of (phenylato)(2-N-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″)-mercury(II), [HgPh(2-NCH₃NCTPP); 7]; the coordination sphere around Hg(1) in 7 was a four-coordinate derivative with a seesaw geometry and dipole–dipole (DD) interaction governed the longitudinal relaxation rate for Hg(1)–Ph–H_2,6 protons of 7 in CDCl₃ (0.01 M) at 599.95 MHz.     

Copper(I) catalysis: Synthesis of N,N′-diarylated and N-aryl,N′-formylated chiral C2-symmetric diamines

Chiral N,N′-diaryl C₂-symmetric diamines and N-aryl,N′-formyl-trans-(1R,2R)-diaminocyclohexane are readily accessed by copper catalyzed N,N′-diarylation and N-aryl,N′-formylation of trans-(1R,2R)-diaminocyclohexane with aryl bromides. N,N′-diarylation using (R)-1,1′-binaphthyl-2,2′-diamine and iodobenzene gave the corresponding (R)-N,N′-diphenyl-1,1′-binaphthyl-2,2′-diamine derivative in 83% yield.     

Reactivity of 2,3-bis(2-pyridyl)pyrazine with [Re2(CO)8(CH3CN)2]: Molecular structures of [Re2(CO)8(C14H10N4)] and [Re2(CO)8(C14H10N4)Re2(CO)8]

The reaction of the labile compound [Re₂(CO)₈(CH₃CN)₂] with 2,3-bis(2-pyridyl)pyrazine in dichloromethane solution at reflux temperature afforded the structural dirhenium isomers [Re₂(CO)₈(C₁₄H₁₀N₄)] (1 and 2), and the complex [Re₂(CO)₈(C₁₄H₁₀N₄)Re₂(CO)₈] (3). In 1, the ligand is σ,σ′-N,N′-coordinated to a Re(CO)₃ fragment through pyridine and pyrazine to form a five-membered chelate ring. A seven-membered ring is obtained for isomer 2 by N-coordination of the 2-pyridyl groups while the pyrazine ring remains uncoordinated. For 2, isomers 2a and 2b are found in a dynamic equilibrium ratio [2a]/[2b]  =  7 in solution, detected by ¹H NMR (−50 °C, CD₃COCD₃), coalescence being observed above room temperature. The ligand in 3 behaves as an 8e-donor bridge bonding two Re(CO)₃ fragments through two (σ,σ′-N,N′) interactions. When the reaction was carried out in refluxing tetrahydrofuran, complex [Re₂(CO)₆(C₁₄H₁₀N₄)₂] (4) was obtained in addition to compounds 1-3. The dinuclear rhenium derivative 4 contains two units of the organic ligand σ,σ′-N,N′-coordinated in a chelate form to each rhenium core. The X-ray crystal structures for 1 and 3 are reported.