Structural, spectral and thermal studies of N-2-(4-picolyl)- and N-2-(6-picolyl)-N′-(2-chlorophenyl)thioureas and N-2-(6-picolyl)-N′-(2-bromophenyl)thiourea

N-2-(4-picolyl)-N′-2-chlorophenylthiourea, 4PicTu2Cl, monoclinic, P2₁/c, a=10.068(5), b=11.715(2), β=96.88(4)°, and Z=4; N-2-(6-picolyl)-N′-2-chlorophenylthiourea, 6PicTu2Cl, triclinic, P-1, a=7.4250(8), b=7.5690(16), c=12.664(3) Å, =105.706(17), β=103.181(13), γ=90.063(13)°, V=665.6(2) ų and Z=2 and N-2-(6-picolyl)-N′-2-bromophenylthiourea, 6PicTu2Br, triclinic, P-1, a=7.512(4), b=7.535(6), c=12.575(4) Å, a=103.14(3), β=105.67(3), γ=90.28(4)°, V=665.7(2) ų and Z=2. The intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen, as well as the planarity of the molecules, are affected by the position of the methyl substituent on the pyridine ring. The enthalpies of fusion and melting points of these thioureas are also affected. ¹H NMR studies in CDCl₃ show the NH′ hydrogen resonance considerably downfield from other resonances in their spectra.     

Structural and spectral studies of N-2-(pyridyl)-, N-2-(3-, 4-, 5-, and 6-picolyl)- and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenylthioureas

Structures of the following compounds have been obtained: N-(2-pyridyl)-N′-2-thiomethoxyphenylthiourea, PyTu2SMe, monoclinic, P2₁/c, a=11.905(3), b=4.7660(8), c=23,532(6) Å, β=95.993(8)°, V=1327.9(5) ų and Z=4; N-2-(3-picolyl)-N′-2-thiomethoxyphenyl-thiourea, 3PicTu2SeMe, monoclinic, C2/c, a=22.870(5), b=7.564(1), c=16.941(4) Å, β=98.300(6)°, V=2899.9(9) ų and Z=8; N-2-(4-picolyl)-N′-2-thiomethoxyphenylthiourea, 4PicTu2SMe, monoclinic P2₁/a, a=9.44(5), b=18.18(7), c=8.376(12) Å, β=91.62(5)°, V=1437(1) ų and Z=4; N-2-(5-picolyl)-N′-2-thiomethoxyphenylthiourea, 5PicTu2SMe, monoclinic, C2/c, a=21.807(2), b=7.5940(9), c=17.500(2) Å, β=93.267(6)°, V=2893.3(5) ų and Z=8; N-2-(6-picolyl)-N′-2-thiomethoxyphenylthiourea, 6PicTu2SMe, monoclinic, P2₁/c, a=8.499(4), b=7.819(2), c=22.291(8) Å, β=90.73(3)°, V=1481.2(9) ų and Z=4 and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenyl-thiourea, 4,6LutTu2SMe, monoclinic, P2₁/c, a=11.621(1), b=9.324(1), c=14.604(1) Å, β=96.378(4)°, V=1572.4(2) ų and Z=4. Comparisons with other N-2-pyridyl-N′-arylthioureas having substituents in the 2-position of the aryl ring are included.     

Design and synthesis of enantiopure 1-[1(S)-(2-pyridyl)alkyl]-2(R)-isopropylaziridines, new ligands for asymmetric catalysis

Enantiopure 1-(2-pyridyl)alkyl aziridines were designed as bidentate ligands for asymmetric catalysis. Their synthesis involved the addition of organometallic reagents to the imine prepared from 2-pyridinealdehyde and an enantiopure β-aminoalcohol, followed by cyclisation of the β-aminoalcohol moiety to the aziridine ring. Two such ligands (N–N)* were prepared from (S)-valinol and converted to the complexes (η³-allyl)(N–N)*Pd⁺SbF₆⁻, one of which was characterised by X-ray crystallography. Modest enantioselectivities were achieved in a representative Pd-catalysed allylic substitution reaction.     

A convenient stereoselective synthesis of (R)-(−)-denopamine and (R)-(−)-salmeterol

β-Adrenoreceptor agonists (R)-(−)-denopamine (R)-1 and (R)-(−)-salmeterol (R)-2 have been prepared in good overall yield and high enantioselectivity through a biotransformative pathway.     

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)-alkenyl)iodonium tetrafluoroborates with tetrabutyl-ammonium halides: retention of configuration

Nucleophilic vinylic substitutions of (Z)-(β-(phenylsulfonyl)alkenyl)-phenyliodonium tetrafluoroborates 1 with tetrabutylammonium halides (Cl, Br, and I) proceed with exclusive retention of configuration at room temperature and afford (Z)-β-(phenylsulfonyl)vinyl halides 2 in high yields.     

Rhenium(I) methoxo carbonyl complexes containing tetraphosphine or triphosphine ligands; facile separation and X-ray crystallographic studies of d/l- and meso-[{Re2(μ-OMe)2(CO)6}2(μ,μ′-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetra-phosphadecane)]

Reaction of the activated mixture of Re₂(CO)_10, Me₃NO and MeOH with a 1:1 mixture of rac (d/l)- and meso-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane (hptpd) yields a mixture of (d/l)- and meso-[{Re₂(μ-OMe)₂(CO)₆}₂(μ,μ′-hptpd)] 1. The diastereomers can be easily separated by selective dissolution of d/l-1 in benzene, and give clearly distinguishable ¹H- and ³¹P-NMR spectra. The fluxional behavior of d/l-1 in solution has been studied by variable-temperature ¹H- and ³¹P-{¹H}-NMR spectroscopy. The crystal structures of both d/l- and meso-1 have been determined. Both molecules consist of two {Re₂(μ-OMe)₂(CO)₆} moieties which are bridged by the two P---CH₂---CH₂---P moieties of the hptpd ligand. Whilst the molecules of meso-1 possess crystallographic i-symmetry, those of d/l-1 do not have any crystallographic symmetry. These diastereomers therefore give clearly distinguishable Raman spectra in the solid state. Reaction of tris[2-(diphenylphosphino)ethyl]phosphine (tdppep) with the activated mixture affords the complex [{Re₂(μ-OMe)₂(CO)₆}(μ,η²-tdppep)] 2, and the analogous reaction involving bis[2-diphenylphospinoethyl)phenylphosphine (triphos) gives [{Re₂(μ-OMe)₂(CO)₆}(μ,μ′,η³-triphos){Re₂(CO)₉}] 3 and [{Re₂(μ-OMe)₂(CO)₆}(μ,η²-triphos)] 4.     

E-2-Benzylidenebenzocycloalkanones. IV. Studies on transmission of substituent effects on C NMR chemical shifts of E-2-(X-benzylidene)-1-tetralones, and -benzosuberones. Comparison with the C NMR data of chalcones and E-2-(X-benzylidene)-1-indanones

Single substituent parameter (SSP) and dual substituent parameter (DSP) analyses were applied to study the transmission of substituent effects on selected ¹³C NMR chemical shifts of the cyclic chalcone analogues, E-2-(4′-X-benzylidene)-1-tetralones (2) and E-2-(4′-X-benzylidene)-1-benzosuberones (3). In order to study how the geometry of the cyclic chalcone analogues affects the transmission of substituent effects similar investigations with the respective chalcones (4) were also performed. The results obtained earlier with the five-membered analogue E-2-(4′-X-benzylidene)-1-indanones (1) were also involved in the comparisons. Geometry optimization of the unsubstituted 1a, 2a, 3a and 4a as well as the substituted 2 and 3 was performed by ab initio quantum chemical calculations. Both SSP and DSP analyses reflected that resonance effects contribute more to the chemical shift of C- (C2), while inductive effects primarily affect that of C-β (C10) of the enone moiety of all the four series. This latter effect, however, is far not as pronounced as that of the former one. It was found that DSP analysis data (ρ_F and ρ_R values) of transmission of substituent effects on the δC2 data can serve as a measure of choice to study the conformation (planarity) of the investigated enones in the four series.     

Synthesis and Crystal Structure of 5-N-i-Propyl-2- （ 2＇ -nitrobenzenesulfonyl） -glutamine

The title compound, 5-N-i-propyl-2-(2′-nitrobenzenesulfonyl)-glutamine, was synthesized and its structure was confirmed by IR, MS, ¹H NMR, and elemental analysis. The single crystal structure of the title compound was determined by X-ray diffraction. The crystal belongs to Monoclinic, space group P2 (1), with a = 0.69281(11) nm, b = 0.76508(12), c = 1.5843(3) nm, = 90°, β = 90.941(3)°, γ = 90°, V = 0.8397(2) nm³, Z = 2, D_c = 1.477 g/cm³, μ = 0.236 mm^-1, F(000) = 392, R = 0.0297, and wR = 0.0664.     

Stereoselective synthesis of (1R,2S)-2-amino-1,3-diols from (R)-cyanohydrins

Vinyl substituted (1R,2S)-amino alcohols 5 were obtained by addition of vinyl magnesium bromide to the corresponding cyanohydrin O-trimethylsilyl ethers (R)-2. The O- and N-protected vinyl amino alcohols 6 were ozonized at −78°C in methanol yielding (1R,2S)-2-amino-1,3-diols7 in high enantiomeric and diastereomeric excesses. For purification, compounds 7 in some cases were acetylated to give the derivatives (1R,2S)-8. Racemic 6a was converted by oxidative ozonolysis at −78°C in methanolic NaOH solution to the corresponding methyl N-acetyl-β-hydroxy propanoate 9a. The configuration of (1R,2S)-8a was confirmed by x-ray crystallographic analysis.     

Steric effects of the 2-(diphenylphosphino)pyridine bridging ligand in the synthesis of binuclear palladium(II) complexes

Treatment of [Pd{CH₂C(CH₃)CH₂}(Ph₂PPy)Cl] (Ph₂PPy = 2-(diphenylphosphino)pyridine) with cis-[Pd(^tBuNC)₂Cl₂] in dichloromethane affords the mixed isocyanide-tertiary phosphine complex cis-[Pd(^tBuNC)Ph₂PPy)Cl₂], in which the Ph₂PPy is a monodentate P-donor, and [{Pd[CH₂C(CH₃)CH₂]Cl}₂]. The steric effects of the Ph₂PPy bridging ligand in determining the reaction course is discussed. The complex cis-[Pd(^tBuNC)(Ph₂PPy)Cl₂] was crystallographically characterized: P2₁/n, a = 15.143(2), b = 9.527(1), c = 17.517(4) Å, β = 113.96(1)°, V= 2309.4(7) ų, Z = 4. The final R value was 0.044, R^w= 0.046 for the 3078 reflections with I > 3σ(I).     

A highly stereoselective synthesis of a key intermediate of 1β-methylcarbapenems employing the reformatsky reaction of 3-(2-bromopropionyl)-2-oxazolidone derivatives

Reaction of sterically crowded achiral 3-(2-bromopropionyl)-2-oxazolidone derivatives with (3 ,4 )-4-acetoxy-3-[( )-1-( -butyldimethylsilyloxy)ethyl]-2-azetidinone in the presence of zinc dust in refluxing tetrahydrofuran was found to give the 1β-methyl substituted β-lactams as major products (at most, β:=95:5). The major products were readily converted into the key intermediate of 1β-methylcarbapenems.     

Azo-containing phosphine complexes of palladium(II) and platinum(II) and their effectiveness in the Heck reaction: crystal and molecular structure of [PdCl2{PPh2{1-(4-MeC6H4N2)-2-OC(O)Me---C10H5}]·2EtOH

Reaction of Na[MCl₄] (M=Pd or Pd) with the azo-containing phosphines Ph₂P{1-(4-RC₆H₄N₂)-2-OR′-C₁₀H₅} {R=Me (I), NMe₂ (II); R′=C(O)Me} affords the complexes [MCl₂L₂] (1–4) in good yield. Complexes 1–4 have all been fully characterised by elemental analysis, ¹H-, ¹³C{¹H}-, and ³¹P{¹H}-NMR spectroscopy and UV–visible spectroscopy. The use of 1 in the Heck reaction has been investigated and shown to effect up to 1000 turnovers.     

A short synthesis of the β-amyloid (Aβ) aggregation inhibitor 3-p-Toluoyl-2-[4′-(3-diethylaminopropoxy)-phenyl]-benzofuran

A short and convenient synthesis of 3-p-toluoyl-2-[4′-(3-diethylaminopropoxy)-phenyl]-benzofuran, an inhibitor of the aggregation of β-amyloid, which is thought to be the underlying cause of Alzheimer's disease, is described.     

Synthesis and derivative chemistry of [Ru2(μ-PPh2) (μ-OH) 2(μ-p-cymene) 2]

The cationic diphenylphosphido-bridged compound [Ru₂(μ-PPh₂)(μ-OH)₂(η⁶-p-cymene)₂][PF₆) (2) has been prepared by reaction of the tri-μ-hydroxo complex [Ru₂(μ-OH)₃(η-p-cymene)₂][PF₆] (1) with diphenylphosphine. Complex 2 eliminates water on reaction with protic acids, incorporating the conjugate base of the added acid as a bridging ligand. Formic acid, acetic acid, phenol, and aniline react with 2 to give the monosubstituted compounds [Ru₂(μ-PPh₂)(μ-OH)(μ-L)(η⁶-p-cymene)₂]PF₆] (L = HCO₂, MeCO₂, OPh, or NHPH), whereas methanol, thiophenol, 1,2-benzenedithiol, hydrochloric acid and isopropanol afford the disubstituted derivatives [Ru₂(μ-PPh₂)(μ-L)₂(η⁶-p-cymene)₂]PF₆] (L = OMe, SPh, S₂C₆H₄, Cl, or H).     

Molecular and crystal structures of N,N′-propylene- and N,N′-phenylene-diylbis [3-(1-aminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione]

Two macrocyclic ligands, N,N′-propylene-diylbis[3-(1-aminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione] I and N,N′-phenylene-diylbis[3-(1-aminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione] II, have been prepared by the condensation of dehydroacetic acid (3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one) with 1,2-phenylenediamine and 1,3-propylenediamine. They have been characterized by means of elemental analysis, IR spectroscopy as well as by X-ray crystallography. The molecular structures of the compounds I and II can be described as consisting of two β-enaminone-2-pyrone rings interlaced with either alkyl chain in I or phenyl ring in II. The X-ray studies confirmed the existence of strong N–HO intramolecular hydrogen bonds in both structures. Their lengths are in accordance to lengths of RAHB intramolecular hydrogen bonds in 1,3-diketones, aryl-hydrazones, β-enaminones and related heterodienes (2.5–2.6 Å) [P. Gilli, V. Bertolasi, V. Ferretti and G. Gilli, J. Am. Chem. Soc., 122 (2000) 10405].     

Versatile reactions of a para-bromophenylacetylide iron(II) derivative and X-ray structure of the fluoro analogue. Synthesis of new redox-active organoiron(II) synthons

The synthesis of the new (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,3-(C₆H₄X) (m-2a/2b; X=F/Br) and (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄I) (2c) complexes, as well as the solid-state structure of the known (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄F) (2a) complex are described. The catalytic coupling reactions of the bromo complexes with various alkynes were next investigated. Starting from the known (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄Br) complex (2b), the synthesis of the (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄)---CC---H complex (6d) and of the corresponding silyl-protected precursors (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄)CC---SiR₃ (6b/6c; R=ⁱPr/Me) are reported. By use of lithium---bromine exchange reactions on 2b, the silyl- (7a; E=Si; R=Me) and tin- (7b–7d; E=Sn; R=Me, Bu, Ph) substituted analogues (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄)ER₃ are also isolated. The spectroscopic and electrochemical characterisations of all these new Fe(II)/Fe(III) redox-active building blocks are presented and the electronic substituent parameters for the “(η²-dppe)(η⁵-C₅Me₅)Fe---CC” group are determined by means of ¹⁹F-NMR.     

Phenylbis(2- pyridyl)phosphine: P- vs. N,N′-coordination in carbonylmolybdenum-(O) and -(II) complexes

The first carbonyl molybdenum-(O) and -(II) complexes with phenylbis(2-pyridyl)phosphine (PPhpy₂) have been synthesized. PPhpy₂ reacts with [Mo(CO)₅(NCMe)] to give [Mo(CO)₅(PPhpy₂-P)]. With [Mo(CO)₄(NBD)] (NBD = norbornadiene) it gives [Mo(CO)₄(PPhpy₂-P)₂] when a 2 : 1 ratio is used, or [MO(CO)₄(py₂PhP---N,N′)] for a 1 : 1 ratio. Decarbonylation of any of these pyridylphosphine complexes leads to an oligomer of formula {MO(CO)₃(μ-PPhpy₂)}_n, which is also obtained after heating [MO(CO)₆] in solution with an equimolar amount of PPhpy₂. The oligomer undergoes oxidative addition by iodine or allylbromide to give [MoI₂(CO)₃(py₂PhP---N,N′)], or [MoBr(η³-CH₂CHCH₂)(CO)₂(py₂PhP---N,N′)], respectively. These complexes are also obtained by addition of equimolar amounts of PPhpy₂ to solutions of [MoI₂(CO)₃(NCMe)₂] and MoBr(η³-CH₂CH CH₂)(CO)₂(NCMe)₂, respectively. The ligand tends to act as a P-donor towards molybdenum(O) substrates, and as a chelating N,N′-donor in molybdenum (II) complexes.     

Reaction of the tetrasulphidomolybdenum(IV) complex LMo(NCS)(S4) with dicarbomethoxyacetylene: X-ray structure of LMo(NCS){S2C2(CO2Me)2} [L = hydrotris(3,5-dimethylpyrazolyl)borate]

The reaction of {HB(Me₂pz)₃}Mo(NCS)(S₄) [HB(Me₂pz)₃⁻ = hydrotris(3,5-dimethylpyrazolyl)borate anion] with dicarbomethoxyacetylene in refluxing toluene results in the formation of the brown, diamagnetic complex {HB(Me₂pz)₃}Mo(NCS){S₂C₂(CO₂Me)₂} (1) (the reactants above also yield 1 upon prolonged reaction in dichloromethane at 25°C), which has been characterized by X-ray crystallography. The mononuclear pseudo-octahedral complex contains a facially tridentate HB(Me₂pz)₃⁻ ligand, a monodentate N-bound NCS⁻ ligand, and a bidentate S₂C₂(CO₂Me)₂²⁻ ligand having a near planar MoS₂C₄ fragment and a SC=CS bond distance of 1.342(15) Å. Solutions of 1 are unstable in air and decompose to produce {HB(Me₂pz)₃}MoO₂(NCS) and {HB(Me₂pz)₃}MoO(NCS)₂.     

Indenyl complexes of ruthenium(II) containing optically active diphosphines. X-ray structures of (S,S)-(η-C9H7)-Ru{Ph2PCH(CH3)CH(CH3)PPh2}Cl and of its η-C5H5 analogue

The optically active indenyl complexes ((η⁵-C₉H₇)Ru(L---L)Cl (where L---L is either (S,S)-1,2-dimethyl-1,2-ethanediylbis(diphenylphosphine) (chiraphos) or (R,R)-1,2-cyclopentanediylbis(diphenylphosphine) (cypenphos)) have been synthesized and spectroscopically characterized and compared with the corresponding cyclopentadienyl complexes. Reaction of the new complexes with 2-e-donors give cationic adducts in which the pentahaptocoordination of the indenyl ligand is maintained. The crystal structures of (S,S)-(η⁵-C₉H₇)Ru{Ph₂PCH(CH₃)CH(CH₃)PPh₂}Cl (1) and (S,S)-η⁵-C₅H₅Ru{Ph₂PCH(CH₃)CH(CH₃)PPh₂}Cl (3) have been determined.     

Iron carbonyl complexes from 2-[2,3-diaza-4-(2-thienyl)buta-1,3-dienyl]thiophene: N---N bond cleavage and cyclometalation

When thienyl Schiff base 1, derived from 2-formylthiophene and hydrazine, reacted with Fe₂(CO)₉ in n-hexane, three major complexes were obtained: (1) a diironhexacarbonyl complex with two 2-thienylmethylideneamido bridging ligands 2, which resulted from the =N---N= bond cleavage of ligand 1; (2) a doubly cyclometalated di-μ-di-(η¹:η²-thienyl; η¹:η¹(N))bis(hexacarbonyldiiron) complex (3); and (3) a cyclometalated (μ-η¹:η²-thienyl; η¹:η¹(N))hexacarbonyldiiron complex (4). Molecular structures of compounds 1a, 1c, and 2a have been determined by single-crystal X-ray diffraction.