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1.
Aliphatic unsaturated cyanohydrins 1-3 served as starting materials in the synthesis of a set of new chiral unsaturated cyclic 1,2-ethanolamines. Combining a Grignard addition-NaBH4 reduction sequence with a ring-closing metathesis afforded unsaturated cyclic 1,2-ethanolamines 7-11 and 22-25 in good yields and high ee (96-99%). The conversion of cyanohydrins 1-3 via a DIBAL reduction-transimination-NaBH4 reduction sequence, using allylamine, followed by ring-closing metathesis yielded tetrahydropyridines 28, tetrahydroazepinols 33 and tetrahydroazocinols 34 in high yields and excellent ee (97-99%). 相似文献
2.
Graphs are partitioned into six classes from the perspective of chirality, depending on whether they are topologically achiral, whether there is at least one topologically achiral embedding, whether there is at least one rigidly achiral embedding, and whether there is at least one rigidly achiral presentation. Three of these classes are well represented by a variety of chemical structures: topologically chiral molecular graphs with no topologically achiral embeddings, topologically chiral molecular graphs with at least one rigidly achiral embedding, and topologically achiral molecular graphs with at least one rigidly achiral presentation. Known representatives of these three classes are described. Various meanings associated with the concepts molecular graph and intrinsic chirality are critically discussed. Previous arrangements of molecular graphs and molecules in a hierarchical order, ranging from the most to the least chiral, are interpreted in terms of the graph's and molecule's chiral persistence. 相似文献
3.
The new developments concerning the possible metrization of structural chirality have drawn much attention recently. The main approach of such quantification is based on the maximal volume overlap between two enantiomorphs of a given chiral set. This approach raises an interesting problem concerning the shape of such a domain of overlap, namely, whether it is chiral or not. It is shown presently that for a two or three dimensional set if the maximal volume overlap is unique then it must beachiral. It is also shown that if a two-dimensional body is convex then by the Brünn-Minkowski theorem the maximal volume overlap of the body with its enantiomorph isachiral. In addition, universal upper bounds for chiral coefficients
n of convex sets in any dimensionn are given, being
2 0.3954 and
3 0.6977 for dimensions two and three, respectively. 相似文献
4.
5.
The neutral complexes [Rh(I)(NBD)((1S)-10-camphorsulfonate)] (2) and [Rh(I)((R)-N-acetylphenylalanate)] (4) reacted with bis-(diphenylphosphino)ethane (dppe) to form the cationic Rh(I)(NBD)(dppe) complexes, 5 and 6, respectively, accompanied by their corresponding chiral counteranions. Analogously, 4 reacted with 4,4′-dimethylbipyridine to yield complex 7. Complexes 5 and 6 disproportionated in aprotic solvents to form the corresponding bis-diphosphine complexes 8 and 9, respectively. 8 was characterized by an X-ray crystal structure analysis. In order to form achiral Rh(I) complexes bearing chiral countercations new sulfonated monophosphines 13-16 with chiral ammonium cations were synthesized. Tris-triphenylphosphinosulfonic acid (H3TPPS, 11) was used to protonate chiral amines to yield chiral ammonium phosphines 14-16. Thallium-tris-triphenylphosphinosulfonate (Tl3TPPS, 12) underwent metathesis with a chiral quartenary ammonium iodide to yield the proton free chiral ammonium phosphine 13. Phosphines 15 and 16 reacted with [Rh(NBD)2]BF4 to afford the highly charged chiral zwitterionic complexes [Rh(NBD)(TPPS)2][(R)-N,N-dimethyl-1-(naphtyl)ethylammonium]5 (17) and [Rh(NBD)(TPPS)2][BF4][(R)-N,N-dimethyl-phenethylammonium]6 (18), respectively. Complexes 5, 6, and 18 were tested as precatalysts for the hydrogenation of de-hydro-N-acetylphenylalanine (19) and methyl-(Z)-(α)-acetoamidocinnamate (MAC, 20) under homogeneous and heterogeneous (silica-supported and self-supported) conditions. None of the reactions was enantioselective. 相似文献
6.
《Tetrahedron: Asymmetry》2003,14(1):1-42
This review gives an updated account on the phenomena of enantioselective perception of chiral fragrances employed in fine and functional perfumery, and of some selected flavours. Differences between enantiomers both in odour quality and strength have been considered.
“Il est des parfums frais comme des chairs d’enfants, | “The perfume is as fresh as the flesh of an infant, | ||||
doux comme les hautbois, verts comme les prairies, | Sweet as an oboe, green as a prairie, | ||||
—et d’autres, corrompus, riches et triomphants, | —And the others, corrupt, rich and triumphant, | ||||
ayant l’expansion des choses infinies | Enlightened by the things of infinity, | ||||
comme l’ambre, le musc, le benjoin et l’encens, | Like amber, musk, benzoin and incense, | ||||
qui chantent les transports de l’esprit et des sens” | That sing, transporting the soul and sense” | ||||
(C. Baudelaire, Les Fleurs du Mal, Correspondances) | (translated by William A. Sigler) |
Entry | Ligands | Solvent | Yieldb (%) | drc (3a : 4a) | eed (%) |
---|---|---|---|---|---|
1 | Yue-1 | EA | 69 | >20 : 1 | 96 (S, R, S) |
2 | Yue-1′ | EA | 64 | 4 : 1 | 33 (S, R, S) |
3 | Yue-2 | EA | 73 | >20 : 1 | 95 (R, S, R) |
4 | Yue-3 | EA | 60 | 6 : 1 | 80 (S, R, S) |
5 | Yue-4 | EA | 44 | 3 : 1 | 85 (S, R, S) |
6 | Yue-5 | EA | 62 | 14 : 1 | 90 (S, R, S) |
7 | L1 | EA | 31 | >20 : 1 | 14 (S, R, S) |
8 | L2 | EA | 42 | >20 : 1 | 73 (S, R, S) |
9 | L3 | EA | — | — | — |
10e | L4 | EA | 64 | 1 : 15 | 77 (S, S, S) |
11e | L4 | DCM | 89 | <1 : 20 | 87 (S, S, S) |
12e,f | L4 | DCM | 89 | <1 : 20 | 86 (S, S, S) |
13e,g | L4 | DCM | 87 | <1 : 20 | 88 (S, S, S) |
14e,h | L4 | DCM | 85 | <1 : 20 | 92 (S, S, S) |