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Showing papers by "J. Fraser Stoddart published in 1984"


Journal ArticleDOI
TL;DR: Enantioselective reductions of prochiral aromatic ketones with adducts formed between ammonia-borane and (2R,3R,11R,12R)-and (2S,3S,11S,12S)-tetraphenyl-1,4,7,10,13,16-hexaoxacyclo-octadecane, (RRRR)-(3) and (SSSS)(3), have afforded the corresponding (S and (R) aromatic secondary alcohols with enantiomeric
Abstract: Enantioselective reductions of prochiral aromatic ketones with adducts formed between ammonia-borane and (2R,3R,11R,12R)- and (2S,3S,11S,12S)-tetraphenyl-1,4,7,10,13,16-hexaoxacyclo-octadecane, (RRRR)-(3) and (SSSS)-(3), have afforded the corresponding (S) and (R) aromatic secondary alcohols with enantiomeric excesses of 20–67%.

31 citations



Journal ArticleDOI
TL;DR: The crystal structures reveal that 18-crown-6 adopts an all-gauche conformation with pseudo D3d symmetry in which the intermolecular N −H ⋯ O hydrogen-bonding interactions between the macrocyclic polyether and the adducts are associated directly with the triangle of oxygen atoms on the complexing face of the crown as discussed by the authors.
Abstract: The macrocyclic polyether 18-crown-6 (C12H24O6) readily forms crystalline 1 : 1 complexes with the adducts BF3NH3 and BH3NH3 Crystals of the solvates BF3NH3·C12H24O6·CH2Cl2 and BH3NH3·C12H24O6·MeOH were suitable for X-ray crystallographic investigation In both cases, the crystal structures reveal that 18-crown-6 adopts an all-gauche conformation with pseudo D3d symmetry in which the intermolecular N–H ⋯ O hydrogen-bonding interactions between the macrocyclic polyether and the adducts are associated directly with the triangle of oxygen atoms on the complexing face of the crown

27 citations



Journal ArticleDOI
TL;DR: The [3.3]cryptand has been separated chromatographically at −5 °C into slowly interconverting in-in ii-(3) and out-out oo-(3)-conformational diastereoisomers [ΔGii→oo→oo‡=ca. 24 kcal mol−1(1 kcal = 4.184 kj) in CD3COCD3 at +38 °C as mentioned in this paper.
Abstract: The [3.3.3]cryptand (3), prepared stereospecifically from 2,3-O-isopropylidene-D-glycerol D-(1) and 2,3-di-O-benzyl-L-glycerol L-(2), has been separated chromatographically at –5 °C into slowly interconverting in-in ii-(3) and out-out oo-(3) conformational diastereoisomers [ΔGii→oo‡=ca. 24 kcal mol–1(1 kcal = 4.184 kj) in CD3COCD3 at +38 °C]; an X-ray structure analysis has shown (3) to from a crystalline 1 : 1 complex with Ba(SCN)2 in which the Ba2+ ion is encapsulated by oo-(3) and the two SCN– ion in an 11-co-ordinate manner.

15 citations



Journal ArticleDOI
TL;DR: The crystal structure of 2NaPF6·dibenzo-36crown-12 was determined by X-ray diffraction methods as discussed by the authors, and the 2:1 (metal:ligand) complex crystallises in the monoclinic system, space group P21/n with cell constants of a = 14.189(2), b = 9.372(1), c = 16.750(3) A, and β = 108.98°.

9 citations



Journal ArticleDOI
TL;DR: Etude de coordinats avec 3 chaines polyether entre 2 noyaux benzeniques, pour les complexes tels que [Rh(cod)(NH 3 ) 2 ][PF 6 ] as discussed by the authors.
Abstract: Etude de coordinats avec 3 chaines polyether entre 2 noyaux benzeniques, pour les complexes tels que [Rh(cod)(NH 3 ) 2 ][PF 6 ]

9 citations


Journal ArticleDOI
TL;DR: In this article, the cristallise dans P2 1 /c avec Z=4 was used for cyclooctadiene-1,5 et C 7 H 8 =norbornadiene. Affinement jusqu'a R=0,034; 0,043 et 0,047 respectivement.
Abstract: [RhC 8 H 12 (NH 3 ) 2 .C 28 H 40 O 10 ] [PF 6 ] cristallise dans P2 1 /c avec Z=4. [RhC 8 H 12 (NH 3 ) 2 .C 24 H 32 O 8 ] [PF 6 ] cristallise dans P2 1 /c avec Z=4. [RhC 7 H 8 (NH 3 ) 2 .C 24 H 32 O 8 ] [PF 6 ] cristallise dans Pbca avec Z=8. Affinement jusqu'a R=0,034; 0,043 et 0,047 respectivement. C 8 H 12 =cyclooctadiene-1,5 et C 7 H 8 =norbornadiene

8 citations



Journal ArticleDOI
TL;DR: Le complexe (1) cristallise dans P1 avec Z=2; affinement jusqu'a R=0,09; as mentioned in this paper, a.k.a.
Abstract: Le complexe (1) cristallise dans P1 avec Z=2; affinement jusqu'a R=0,09. Le complexe (2) cristallise dans P2 1 /c avec Z=4; affinement jusqu'a R=0,201

Book ChapterDOI
TL;DR: This chapter discusses the contributions that have been made by synthetic molecular receptors of the crown ether type to the development of enzyme mimics and analogues in the context of crown ether hosts.
Abstract: Publisher Summary This chapter discusses the contributions that have been made by synthetic molecular receptors of the crown ether type to the development of enzyme mimics and analogues. A complementary steric and electronic relationship between a substrate species and a synthetic molecular receptor is desirable if strong and highly ordered complex formation is to occur. Because the potential binding sites in the smaller substrate are divergent, the larger molecular receptor has to be designed with matching convergent binding sites. This relationship is a reminiscent of the lock and key model, which was proposed many years ago to describe the interaction between an enzyme and its substrate. A more recent nomenclature system advocated by Cram and co-workers, that employs the terms “host” and “guest” respectively to refer to the crown ether molecular receptor and the substrate, has now gained popular acceptance. In the context of crown ether hosts, non-covalent bonds of pole–pole, pole–dipole, and dipole–dipole types can be employed in the formation of host–guest complexes.