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91.
Surprisingly Different Reaction Behavior of Alkali and Alkaline Earth Metal Bis(trimethylsilyl)amides toward Bulky N‐(2‐Pyridylethyl)‐N′‐(2,6‐diisopropylphenyl)pivalamidine
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Diana Kalden Ansgar Oberheide Dr. Claas Loh Dr. Helmar Görls Dr. Sven Krieck Prof. Dr. Matthias Westerhausen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10944-10959
N‐(2,6‐Diisopropylphenyl)‐N′‐(2‐pyridylethyl)pivalamidine (Dipp‐N=C(tBu)‐N(H)‐C2H4‐Py) ( 1 ), reacts with metalation reagents of lithium, magnesium, calcium, and strontium to give the corresponding pivalamidinates [(tmeda)Li{Dipp‐N=C(tBu)‐N‐C2H4‐Py}] ( 6 ), [Mg{Dipp‐N=C(tBu)‐N‐C2H4‐Py}2] ( 3 ), and heteroleptic [{(Me3Si)2N}Ae{Dipp‐N=C(tBu)‐N‐C2H4‐Py}], with Ae being Ca ( 2 a ) and Sr ( 2 b ). In contrast to this straightforward deprotonation of the amidine units, the reaction of 1 with the bis(trimethylsilyl)amides of sodium or potassium unexpectedly leads to a β‐metalation and an immediate deamidation reaction yielding [(thf)2Na{Dipp‐N=C(tBu)‐N(H)}] ( 4 a ) or [(thf)2K{Dipp‐N=C(tBu)‐N(H)}] ( 4 b ), respectively, as well as 2‐vinylpyridine in both cases. The lithium derivative shows a similar reaction behavior to the alkaline earth metal congeners, underlining the diagonal relationship in the periodic table. Protonation of 4 a or the metathesis reaction of 4 b with CaI2 in tetrahydrofuran yields N‐(2,6‐diisopropylphenyl)pivalamidine (Dipp‐N=C(tBu)‐NH2) ( 5 ), or [(thf)4Ca{Dipp‐N=C(tBu)‐N(H)}2] ( 7 ), respectively. The reaction of AN(SiMe3)2 (A=Na, K) with less bulky formamidine Dipp‐N=C(H)‐N(H)‐C2H4‐Py ( 8 ) leads to deprotonation of the amidine functionality, and [(thf)Na{Dipp‐N=C(H)‐N‐C2H4‐Py}]2 ( 9 a ) or [(thf)K{Dipp‐N=C(H)‐N‐C2H4‐Py}]2 ( 9 b ), respectively, are isolated as dinuclear complexes. From these experiments it is obvious, that β‐metalation/deamidation of N‐(2‐pyridylethyl)amidines requires bases with soft metal ions and also steric pressure. The isomeric forms of all compounds are verified by single‐crystal X‐ray structure analysis and are maintained in solution. 相似文献
92.
93.
Thomas Billot Rainer Beckert Manfred Dring Jrg Wuckelt Peer Fehling Helmar Grls 《Journal of heterocyclic chemistry》2001,38(1):205-211
The synthesis of pyrido[2,1‐c]‐1,2,4‐triazines 6 , pyrido[1,2‐b]‐1,2,4‐triazines 7 and pyrido[1,2‐b]pyri‐dazines 8 respectively by cycloacylation of derivatives of pyridine with imidoylchlorides of type 2 is described. The heterocycles of type 6 as well as of type 7 can be ring‐transformed with dimethyl acetylenedicarboxylate. In contrast to pyrido[1,2‐a]pyrazines 1, a complex reaction including cleavage of the acetylene subunit takes place. Starting from compound 6a , the pyrrolo[2,3‐d]imidazole 11a could be isolated from a mixture of unidentified by‐products, whereas derivatives 7 gave nearly quantitatively the tricyclic products of type 12 . 相似文献
94.
95.
Transmetalation of Sn[N(SiMe3)2]2 with calcium granules in tetrahydropyran (thp) yields colorless [(thp)2Ca{N(SiMe3)2}2] ( 1 ) which is soluble in common organic solvents. The calcium center is in a distorted tetrahedral environment with Ca–N and Ca–O bond lengths of 231.08(11) and 240.23(9) pm, respectively. The molecular structure is dominated by steric factors leading to a NCaN bond angle of 119.43(6)°. 相似文献
96.
Abstract The dynamic mechanical properties of polystyrene/ethyl benzene, polymethyl methacrylate/water, polyethyl methacrylate/ethyl hexyl adipate, and poly-2-hydroxyethyl methacrylate/water were studied between 10 and 100°K. A free-decay resonance acoustic spectrometer was designed for this purpose. It was found that the presence of diluents causes the low-temperature loss peaks of the polyrners in question to shift to higher temperatures. This observation is compatible with the hypothesis that at very low temperatures, the diluent molecules are immobilized to occupy free space between adjacent polymer chains. The hindering action of these molecules on the kinetic motions of the side groups of the polymer thus renders greater thermal energy necessary to initiate the relaxation processes. 相似文献
97.
Lithium 8‐amidoquinoline ( 1 ) and lithium 8‐(trialkylsilylamido)quinoline [SiMe2tBu ( 2 ), SiiPr3 ( 3 )] react with dimethylgallium chloride to the metathesis products dimethylgallium 8‐amidoquinoline ( 4 ) as well as dimethylgallium 8‐(trialkylsilylamido)quinoline [SiMe2tBu ( 5 ), SiiPr3 ( 6 )]. The gallium atoms are in distorted tetrahedral environments. During the synthesis of 5 , orange dimethylgallium 2‐butyl‐8‐(tert‐butyldimethylsilylamido)quinoline ( 7 ) was found as by‐product. The metathesis reactions of Me2GaCl with LiN(R)CH2Py (Py = 2‐pyridyl) yield the corresponding 2‐pyridylmethylamides Me2Ga‐N(H)CH2Py ( 8 ), Me2Ga‐N(SiMe2tBu)CH2Py ( 9 ) and Me2Ga‐N(SiiPr3)CH2Py ( 10 ). In these complexes the gallium atoms show a distorted tetrahedral coordination sphere. However, derivative 8 crystallizes dimeric with bridging amido units whereas in 9 and 10 the 2‐pyridylmethylamido moieties act as bidentate ligands leading to monomeric molecules. 相似文献
98.
Benjamin Schulze Dr. Daniel Escudero Christian Friebe Dr. Ronald Siebert Dr. Helmar Görls Stephan Sinn Martin Thomas Sebastian Mai Prof. Dr. Jürgen Popp Prof. Dr. Benjamin Dietzek Prof. Dr. Leticia González Prof. Dr. Ulrich S. Schubert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(13):3785-3785
99.
Treatment of the ruthenium chloride, CpRu(PPh3)2Cl, with the alkynyldithiocarboxylate anions, , in refluxing THF affords the chelate complexes CpRu(PPh3)(κ2S,S-S2CCCR) (1) (R = But (a), Bun (b), Ph (c), SiMe3 (d)) in high yield. The room temperature reaction of the solvated species, [CpRu(PPh3)2(NCPh)]+, with the alkynyldithiocarboxylate anions, , produces the chelate complexes 1 and the mono-coordinated complexes CpRu(PPh3)2(κS-S2CCCR) (2). Complexes 2 are converted to 1 in solution so that they were characterized spectroscopically. 相似文献
100.
Schäfer B Görls H Presselt M Schmitt M Popp J Henry W Vos JG Rau S 《Dalton transactions (Cambridge, England : 2003)》2006,(18):2225-2231
The synthesis and photophysical properties of a series of substituted dipyridophenazine (dppz) ruthenium complexes of the type [(tbbpy)2Ru(dppz-R2)]2+ (where tbbpy = 4,4-tert-butyl-2,2-bipyridine and dppz = dipyrido[3,2-a:2',3'-c]phenazine and R represents substitution at the 11 and 12 position with: Br, phenyl, 4-tert-butyl-phenyl and para-biphenyl) are described. The ligands could be obtained in high yields using Suzuki-type coupling reactions, an approach which also has been successfully applied to the analogous dppz-Br2 ruthenium complex. All compounds are fully characterised by NMR, MS and UV-vis spectroscopy. The solid state structures of dppz-bi-para-biphenyl and the ruthenium complex [(tbbpy)2Ru(dppz-Br2)]2+ are also reported. The investigation of the free ligands reveals a pronounced effect of the arylic substitution on absorption and emission properties. These properties are mirrored in the corresponding complexes, which possess emission lifetimes of up to 900 ns. The resonance Raman investigation of the complex [(tbbpy)2Ru(dppz-Br2)]2+ supports the assumption that the excited state properties of the substituted complexes are related to the parent [(bpy)2Ru(dppz)]2+ compound, but that important differences may be expected based on the differences observed in the lowest energy absorption band. 相似文献