Substituent Effects in the Reactions of Some Polysubstituted 4-Hydroxy-4-methylcyclohexa-2,5-Dienones With Hydroxide Ion; X-Ray Structure Analyses of 2,5,6-Tribromo-3,4-dihydroxy-4-methylcyclohexa-2,5-dienone and 3,4-Dibromo-5-methyl-5-nitroacetylfuran-2(5H)-one

1987 ◽  
Vol 40 (10) ◽  
pp. 1769 ◽  
Author(s):  
MJ Gray ◽  
MP Hartshorn ◽  
WT Robinson ◽  
J Vaughan
Keyword(s):  
Substituent Effects ◽  
Hydroxide Ion ◽  
X Ray ◽  
Effect Of Substituents ◽  
Structure Determinations ◽  
Ion Treatment

Reactions of the 2,3,5,6-substituted 4-hydroxy-4-methylcyclohexa-2,5-dienones (6a), (6b), (7a) and (7b) with hydroxide ion give 3,4-dihydroxy dienones (9a), (9b), (10) and (11). In contrast, hydroxide ion treatment of the substituted nitro dienone (8), followed by acidification, gives the substituted furan-2(5H)-one (12). The effect of substituents on the course of the reactions is discussed. X-ray structure determinations for compounds (9a) and (12) are reported.

Substituent Effects in the Crystal Structures of Isoxindigos [(E)-3,3'-Bibenzofuranylidene-2,2'-diones]

1985 ◽  
Vol 38 (1) ◽  
pp. 85 ◽  
Author(s):  
H Becker ◽  
CL Raston ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Steric Effect ◽  
Substituent Effects ◽  
Steric Effects ◽  
Asymmetric Unit ◽  
X Ray ◽  
Benzene Rings ◽  
Fused Ring ◽  
Structure Determinations

Single-crystal X-ray structure determinations of the parent isoxindigo (1), C16H8O4, together with those of derivatives substituted in both benzene rings with ( i ) t-butyl groups in the 5- and 7-positions [derivative (2)] and (ii) methoxy and t-butyl groups in the 5- and 7- positions respectively [two polymorphs, (3α,8)] have been determined in order to examine the possibility of distortion of molecular planarity by substituent steric effects, and the spectroscopic consequences thereof. Crystals of (1) are monoclinic, P21/n, a 17.69(1), b 5.690(3), c5.693(3)Ǻ, β 100.52(5)�, Z 2; after least-squares refinement, a residual R 0.067 was obtained for No 385 ?observed? Independent reflections. For (2), C32H40O4, crystals are monoclinic, P21/n, a 16.402(8), b 12.313(6), c 13.913(8)Ǻ, β 96.75(4)�, Z4; R 0.088 for No 1261. For (3), C26H28O6 (α-form), crystals are orthorhombic, Pcab , a 10.449(4), b 12.477(4), c 17.825(6)Ǻ, Z 4; R 0.058 for No 959; in the case of the β-form of (3), crystals are monoclinic, P21/n, a 6.828(2), b 15.464(3), c 10.770(3) Ǻ, β 98.58(4)�, Z 2. In (1) and (3α,β), the molecules all lie disposed about crystallographically imposed symmetry elements, with one-half of the molecule, with a substantially planar fused-ring skeleton, comprising the asymmetric unit. In (2), the full molecule is the asymmetric unit; the fused-ring skeletons are substantially planar also, but the molecule exhibits a substantial twist about the bond connecting the two halves, with an interplanar dlhedral angle of 16.8°. This is ascribed to the steric effect of the large and more numerous t-butyl substituents.

Alkyl Substituent Effects in Diamagnetic Dithiocarbamate Cobalt(III) and Nickel(II) Complexes

1990 ◽  
Vol 43 (6) ◽  
pp. 1083 ◽  
Author(s):  
PC Healy ◽  
JW Connor ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Field Strength ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Aliphatic Hydrocarbon ◽  
Ligand Field ◽  
Space Group ◽  
X Ray ◽  
Dithiocarbamate Ligand ◽  
Structure Determinations ◽  
Study Support

Single-crystal X-ray structure determinations have been recorded at 295 K for the tris(dithiocarbamato)cobalt(III) compounds: [Co(S2CN(CH2)4)3], [Co(S2CNEt2)3] (redeterminations), [Co(S2CN(CH2Ph)2)3], and [Co(S2CNPri2)3] at 120 and 295 K. [Co(S2CN(CH2)4)3] crystallizes in the space group C2/c with a 28.984(15), b 14.416(2), c 16.206(15)Ǻ, β 104.20(5)°, Z 12; [Co(S2CNEt2)3] also crystallizes in space group C2/c with a 14.097(3), b 10.305(2), c 17.070(7)Ǻ, β 110.19(3)°, Z 4; [Co(S2CN(CH2Ph)2)3] crystallizes in space group P21 with a 11.851(6), b 29.920(8), c 12.395(3)Ǻ, β 97.74(4)°; [Co(S2CNPri2)3] crystallizes in space group R3c with a 13.367(6)Ǻ, α 58.04(2)° (295 K); a 13.155(6)Ǻ, α 58.59(3)° (120 K), Z 2. The structure of [Ni(S2CNPri2)2] has been redetermined, the complex crystallizing in the space group P21/c with a 8.147(2), b 17.820(3), c 15.630(3)Ǻ, β 110.32(2)°, Z 4. The results obtained from this study support the hypothesis, put forward by Ymen and Stahl, that the influence of aliphatic hydrocarbon substituents on the ligand-field strength at the sulfur atoms of the dithiocarbamate ligand is not through the π bonding network of the conjugated S2CN moiety, but, rather, intraligand S…H-C interactions which increase with increasing bulk of the substituent atoms. Unlike the free anion systems, or the iron(III) complexes, however, the changes in the S-C-S angles with increasing field strength, while observable, are very small.

Chiral Resolution of Hexaamine Cobalt(III) Cages: Substituent Effects on Chiral Discrimination

2003 ◽  
Vol 56 (12) ◽  
pp. 1187 ◽  
Author(s):  
Paul V. Bernhardt ◽  
Tri Erny Dyahningtyas ◽  
Jack M. Harrowfield ◽  
Jee-Young Kim ◽  
Yang Kim ◽  
...  
Keyword(s):  
Complex Anion ◽  
Substituent Effects ◽  
Outer Sphere ◽  
Exchange Chromatography ◽  
Chiral Resolution ◽  
Chiral Discrimination ◽  
Pairing Interaction ◽  
X Ray ◽  
Selective Crystallization ◽  
Bonding Interaction

Chiral resolution of the cobalt cage complexes [Co(diNOsar)]3+ and [Co(diAMsarH2)]5+ have been achieved by selective crystallization with the anion bis-μ-(R), (R)-tartratodiantimonate(III) ([Sb2(R,R-tart)2]2–) and also by column chromatography with Na2[Sb2(R,R-tart)2] as eluent. The X-ray crystal structures of Λ-[Co(diNOsar)][Sb2(R,R-tart)2]Cl . 7 H2O and Δ-[Co(diAMsarH2)][Sb2(R,R-tart)2]2Cl . 14 H2O are reported, which reveal an unexpected reversal of chiral discrimination when the cage substituent is changed from nitro (Λ-enantiomer) to ammonio Δ-enantiomer) and shows that the ammonio-substituted cage is capable of forming a three-point hydrogen-bonding interaction with each complex anion, whereas the nitro analogue can only form two hydrogen bonds with each [Sb2(R,R-tart)2]2– anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na2[Sb2(R,R-tart)2] as eluent, Λ-[Co(diNOsar)]3+ elutes first, which implies a tighter ion pairing interaction than for the Δ-enantiomer. On the other hand, Δ-[Co(diAMsarH2)]5+ elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between Δ-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2– relative to Λ-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2–.

Preparations, X-ray crystal structure determinations, and base strength measurements of substituted tritylamines

2000 ◽  
pp. 85-92 ◽  
Author(s):  
Moisés Canle L. ◽  
William Clegg ◽  
Ibrahim Demirtas ◽  
Mark R. J. Elsegood ◽  
Howard Maskill
Keyword(s):  
Crystal Structure ◽  
X Ray ◽  
Structure Determinations ◽  
Base Strength

Comparative Structural Studies on Three-Coordinate Copper(I) Halide Complexes With Tertiary Phosphines. Crystal Structures of [(PPh2Mes)CuX]2 and [(PPhMes2)CuX]2 (Mes = Mesityl X = Cl, Br, I)

1992 ◽  
Vol 45 (7) ◽  
pp. 1155 ◽  
Author(s):  
GA Bowmaker ◽  
D Camp ◽  
RD Hart ◽  
PC Healy ◽  
BW Skelton ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Copper Atom ◽  
Structural Studies ◽  
Coordination Environment ◽  
X Ray ◽  
Tertiary Phosphines ◽  
Structure Determinations ◽  
Halide Complexes ◽  
The Subject

The 1 : 1 complexes of the substituted triphenylphosphine ligands mesityldiphenylphosphine and dimesitylphenylphosphine with copper(1) chloride, bromide and iodide have been the subject of single-crystal X-ray structure determinations at 295 K. All six complexes crystallize as air-stable dimeric molecules, [(PPh2Mes)CuX]2 and [ (PPhMes2)CUX]2 with each copper atom in a distorted trigonal PCuX2. coordination environment. Crystals of [(PPh2Mes)CuCl]2 (1) are monoclinic, P21/n, a 9.961(3), b 18.687(6), c 11.009(7) Ǻ, β 114.63(4)°; R was 0.049 for 2450 'observed' reflections. [(PPh2Mes)CuBrI2 (2) is monoclinic, P21/n, a 9.939(2), b 18.832(6), c 11.238(6) Ǻ, β 115.36(3)°; R was 0.046 for 1803 'observed' reflections. [(PPh2Mes)CuI]2.4/3 C6H6 (3) is rhornbohedral, R3, a 36.877(8), c 9.047(5) A; R was 0.039 for 2537 'observed' reflections. Crystals of [(PPhMes2)CuCl]2.2MeCN (4) are triclinic, Pi, a 15.783(7), b 9.570(4), c 8.914(4) Ǻ, α 72.43(3), β 76.37(3), γ 74.03(3)°; R was 0.045 for 3341 'observed' reflections. [(PPhMes2)CuBr]2.3C6H6 (5) is monoclinic, C2/c, a 9.694(6), b 30.15(2), c 20.66(2) Ǻ, β 98.00(7)°; R was 0.047 for 2117 'observed' reflections. [(PPhMes2)CuI]2.2MeCN (6) is orthorhombic, PP1nb, a 11.694(8), b 14.77(1), c 29.76(3) Ǻ; R was 0.049 for 3447 'observed' reflections. Cu-P bond lengths are: 2.196(2) A (1); 2.198(3) Ǻ (2); 2.222(5) and 2.226(5) Ǻ (3); 2.202(1) Ǻ (4); 2.197(3) A (5); 2.201(4) and 2.264(5) Ǻ (6). The geometries of the LCuX2 and CuX2Cu units are compared with data reported for other monomeric and dimeric compounds for both phosphorus- and nitrogen-based ligands L.

Approaches to the Synthesis of Lincosamine, a Derived Portion of the Antibiotic Lincomycin

1990 ◽  
Vol 43 (10) ◽  
pp. 1657 ◽  
Author(s):  
LM Engelhardt ◽  
BW Skelton ◽  
RV Stick ◽  
DMG Tilbrook ◽  
AH White
Keyword(s):  
Nitrogen Atom ◽  
Single Crystal ◽  
Structure Elucidation ◽  
X Ray ◽  
Structure Determinations

A variety of approaches towards the synthesis of lincosamine, a derived portion of the antibiotic lincomycin , are reported. Initial approaches involved the intramolecular delivery of a nitrogen atom ( trichloroacetimidate , trichloroacetylcarbamate , carbamate, 2-amino-2- phenylacetate ) attached to O4 onto C6 of a 6,7-anhydrooctoside. Later approaches, albeit more direct but again largely unsuccessful, involved the Sharpless titanium(IV)-mediated nucleophilic opening of a suitable 6,7-anhydrooctose, and the Sharpless oxyamination and the aziridination of suitable octenoses . As an aid to the structure elucidation of several compounds encountered in this work, single-crystal X-ray structure determinations are reported for methyl 6,7-anhydro-2,3-di-O-benzyl-8-deoxy-α-D-threo-D-galacto-octopyranoside , methyl 6,7-anhydro-2,3-di-O-benzyl-8-deoxy-α-D-threo-D-gluco-octopyranoside and 7-azido-7-deoxy-1,2:3,4-di-O-isopropylidene-β-L-erythro-Dgalacto-octose.

Sign in / Sign up

Export Citation Format

Share Document