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101.
Hoffmann RW Nell PG Leo R Harms K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(18):3359-3365
alpha-Chloro- and alpha-bromoalkyl Grignard reagents 11 and 30 with > 97% ee (enantiomeric excess) were generated by a sulfoxide/magnesium exchange reaction from the enantiomerically and diastereomerically pure sulfoxides 25 and 27. The resulting alpha-haloalkyl Grignard reagents are configurationally stable at -78 degrees C. Racemization sets in at or above -60 degrees C, especially when the solution contains bromide ions. In the absence of halide ions, the configurational stability extends up to -20 degrees C, when chemical decomposition commences. 相似文献
102.
Pentazole Derivates and Azides Formed from them: Potassium‐Crown‐Ether Salts of [O3S—p‐C6H4—N5]— and [O3S—p‐C6H4—N3]— —O3S—p‐C6H4—N2+ was reacted with sodium azide at —50 °C in methanol, yielding a mixture of 4‐pentazolylbenzenesulfonate and 4‐azidobenzenesulfonate (amount‐of‐substance ratio 27:73 according to NMR). By addition of KOH in methanol at —50 °C a mixture of the potassium salts K[O3S—p‐C6H4—N5] and K[O3S—p‐C6H4—N3] was precipitated (ratio 60:40). A solution of this mixture along with 18‐crown‐6 in tetrahydrofurane yielded the crystalline pentazole derivate [THF‐K‐18‐crown‐6][O3S—p‐C6H4—N5]·THF by addition of petrol ether at —70 °C. From the same solution upon evaporation and redissolution in THF/petrol ether the crystalline azide [THF‐K‐18‐crown‐6][O3S—p‐C6H4—N3]·THF was obtained. A solution of the latter in chloroform/toluene under air yielded [K‐18‐crown‐6][O3S—p‐C6H4—N3]·1/3H2O. According to their X‐ray crystal structure determinations [THF‐K‐18‐crown‐6][O3S—p‐C6H4—N5]·THF and [THF‐K‐18‐crown‐6][O3S—p‐C6H4—N3]·THF have the same kind of crystal packing. Differences worth mentioning exist only for the atomic positions of the pentazole ring as compared to the azido group and for one THF molecule which is coordinated to the potassium ion; different orientations of the THF molecule take account for the different space requirements of the N5 and the N3 group. In [K‐18‐crown‐6][O3S—p‐C6H4—N3]·1/3H2O there exists one unit consisting of one [K‐18‐crown‐6]+ and one [O3S‐C6H4—N3]— ion and another unit consisting of two [O3S‐C6H4—N3]— ions joined via two [K‐18‐crown‐6]+ ions and one water molecule. The rate constants for the decomposition [O3S‐C6H4—N5]— → [O3S‐C6H4—N3]— + N2 in methanol were determined at 0 °C and —20 °C. 相似文献
103.
Wolfgang Hiller Stephanie Frey Joachim Strähle Gernot Boche Wolfgang Zarges Klaus Harms Michael Marsch RenéA Wollert Kurt Dehnicke 《欧洲无机化学杂志》1992,125(1):87-92
The Crystal Structures of {Li3(12-crown-4)2[HC(CN)2]3}, {Na(15-crown-5)[HC(CN)2]}, and {NaN(nBu)4[HC(CN)2]2 · THF} The preparation and the crystal structures of the title compounds 1 — 3 are described. 1 forms a polymeric chain structure, in which one of the lithium ions is linked by Li…NCC(H)CN… bridges. The remaining lithium ions form (12-crown-4)Li[NCC(H)CN] units, which are coordinated by one of the nitrogen atoms of the dicyanomethanide ions with the lithium ions of the chain. 2 forms an ion pair, in which the sodium ion is coordinated by the five oxygen atoms of the crown ether molecule and by one nitrogen atom of the dicyanomethanide ion. 3 has a threedimensional network, in which the sodium ions are coordinated in a distorted tetrahedral manner by the nitrogen atoms of the dicyanomethanide ions. In the cavities of the network the tetrabutylammonium ions and the THF molecules are found. 相似文献
104.
The cobalt(I)-catalyzed Diels-Alder reaction of nonactivated aryl alkynyl sulfides with acyclic 1,3-dienes generates dihydroaromatic vinyl sulfides under very mild reaction conditions, and these products can be oxidized with mild oxidants to the corresponding diaryl sulfides in good overall yields. The steric and electronic effects of substituents on the aryl, as well as on the alkynyl, moieties of the aryl alkynyl sulfide are discussed. While the cobalt catalyst system is quite efficient in converting alkynyl sulfides to the Diels-Alder adducts, the transformation of the corresponding aryl alkynyl sulfoxides and sulfones under similar mild reaction conditions gave only moderate yields of the desired adducts. 相似文献
105.
John M Auel C Behrens C Marsch M Harms K Bosold F Gschwind RM Rajamohanan PR Boche G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(16):3060-3068
From Li+ well-solvating solvents or complex ligands such as THF, [12]crown-4, amines etc., lithium cuprates R2CuLi(*LiX) crystallise in a solvent-separated ion pair (SSIP) structural type (e.g. 10). In contrast, solvents with little donor qualities for Li+ such as diethyl ether or dimethyl sulfide lead to solid-state structures of the contact ion pair (CIP) type (e.g. 11). 1H,6Li HOESY NMR investigations in solutions of R2CuLi(*LiX) (15, 16) are in agreement with these findings: in THF the SSIP 18 is strongly favoured in the equilibrium with the CIP 17, and in diethyl ether one observes essentially only the CIP 17. Salts LiX (X=CN, Cl, Br, I, SPh) have only a minor effect on the ion pair equilibrium. These structural investigations correspond perfectly with Bertz's logarithmic reactivity profiles (LRPs) of reactions of R2CuLi with enones in diethyl ether and THF: the faster reaction in diethyl ether is due to the predominance of the CIP 17 in this solvent, which is the reacting species; in THF only little CIP 17 is present in a fast equilibrium with the SSIP 18. A kinetic analysis of the LRPs quantifies these findings. Recent quantum-chemical studies are also in agreement with the CIP 17 being the reacting species. Thus a uniform picture of structure and reactivity of lithium cuprates emerges. 相似文献
106.
107.
The title compounds 1a-c and 2 werre reacted with several doubly activated methylene components to yield the cyclic ketene S,N-acetals 3-10 . 相似文献
108.
Ga2Br2R2 and Ga3I2R3 [R = C(SiMe3)3] — Two New Organoelement Subhalides of Gallium Containing One or Two Ga‐Ga Single Bonds The oxidation of the tetrahedral tetragallium cluster Ga4[C(SiMe3)3]4 ( 1 ) with elemental bromine in the presence of AlBr3 yielded the corresponding gallium subhalide Ga2Br2R2 [ 4 , R = C(SiMe3)3], which remains monomer even in the solid state and in which the GaII atoms are connected by a short Ga‐Ga single bond [243.2(2) pm]. The analogous diiodide Ga2I2R2 ( 3 ), which was obtained on a similar route by our group only recently, did not react with lithium tert‐butanolate by substitution as originally expected. Instead, partial disproportionation occurred with the formation of the trigallium diiodide Ga3I2R3 ( 6 ), in which three Ga atoms are connected by two Ga‐Ga single bonds (255.1 pm on average). Both terminal Ga atoms have a coordination number of four owing to the bridging function of both iodine atoms, while the inner one which has an oxidation number of +1 remains coordinatively unsaturated. An average oxidation state of 1.66 resulted for all atoms of the chain. The GaIII compound {[GaI(R)(OCMe3)(OH)]Li}2 ( 7 ) was isolated as the second product of the disproportionation. It is a dimer in the solid state via Li‐O bridges and shows a hindered rotation of its tert‐butyl group. 相似文献
109.
110.