Metallorganische Verbindungen XIX: Reaktionen der Aluminium‐ Wasserstoff‐Bindung mit Olefinen

Ziegler, K.; Gellert, Hans‐Georg; Martin, H.; Nagel, K.; Schneider, Jennifer

doi:10.1002/jlac.19545890202

Cited by 184 publications

(25 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In accordance with the reported data [1,8] and the investigations of Zakharkin [9] , LiAlH 4 hydroaluminates α -olefi ns at higher temperatures (100 -130 ° C), compared with AlH 3 , producing the corresponding lithium tetraalkylalanates (5) , which further react with AlCl 3 yielding trialkylalanates (6) (Scheme 18.4 ).…”

Section: Alkenessupporting

confidence: 72%

Hydrometallation of Unsaturated Compounds

Джемилев

Ибрагимов

2008

Modern Reduction Methods

View full text Add to dashboard Cite

18 IntroductionTo the number of signifi cant hydrometallating reagents that have been introduced into organic synthesis should be added the stable hydrides of transition metals (Zr) and nontransition metals (B, Al, Mg).Today, hydrides of the these metals and their derivatives are widely used in the reduction of alkenes, dienes, alkynes, allenes, heteroolefi ns and carbonyl compounds as well as for the production of the corresponding organometallic compounds and selective alkene functionalization via the synthesis of compounds containing polar metal -carbon (M − C) bonds. These may be involved in reactions with electrophilic or nucleophilic reagents affording functional derivatives.Generally, the thermal additions of the above hydrides to alkenes proceed via the four -center transition state (1) , with subsequent cleavage of the M − H bond and metal addition. In this case the corresponding organometallic compounds are formed according to Scheme 18.1 .The use of metal complex catalysts in organic and metalloorganic chemistry allows the chemo -, regio -and stereoselective hydroalumination of unsaturated compounds under mild conditions with high yields.The role of a transition metal catalyst in these reactions is determined by its ability to activate the starting substrate by coordination to the metal center forming the intermediate hydride complex (2) . The latter, being a more active hydrometallating reagent, attacks alkenes under mild conditions with subsequent transmetallation of the starting hydride affording the target organic compound (3) according to Scheme 18.2 .To date, a large number of reports have appeared in the literature on the application of hydride reagents in both thermal and catalytic hydrometallation of unsaturated compounds. Hydroboration, hydroalumination, hydrozirconation and hydromagnesiation of unsaturated compounds such as alkenes, dienes or alkynes are considered the most effective reactions for producing the related metalloorganic compounds. It is not possible to consider all these reactions within the

show abstract

Section: Alkenessupporting

confidence: 72%

Hydrometallation of Unsaturated Compounds

Джемилев

Ибрагимов

2008

Modern Reduction Methods

View full text Add to dashboard Cite

show abstract

“…I), the complex m's of H-C(2) and H-C (6) are missing, and the signals of the bridgehead protons H-C(l) and H-C(7) are shifted towards higher frequencies by 0.7 and 0.9 ppm due to the adjacent C=C bond. Otherwise, besides the fact that the splittingpattern of CH2 (9) and CHI@) is approaching that of AA'XX'YZ spectrum (because pairs of protons are nearly equivalent), all the features of the alkyl range of the spectrum of 22 are very similar to those of dibromide 23.…”

Section: Bromination/elimination Experiments With a Modelmentioning

confidence: 79%

Synthetic Attempts towards Polymers with Pentafulvene Structural Units

Zhang

Neuenschwander

1995

Helvetica Chimica Acta

View full text Add to dashboard Cite

Synthetic attempts towards fully conjugated polymers 9 with pentafulvene-diyl structural units are described. Cationic polymerization of pentafulvenes la (R = X = Me) and lb (R = X = MeS) nearly quantitatively gives polymers 8a and Sb with typical M , and M , values of 38800 and 53750, respectively, for 8a, and 12000 and 35900, respectively, for 8b. Key step of the conversion 8a + 9a (Scheme 6 ) is a quantitative bromination Sa -+ 32a, the structure of 32a being confirmed by analytical data as well as by spectroscopic comparison with model compound 23. Best results in view of two-fold the HBr elimination 32a + 9a are obtained with Et,N, but so far elimination has not been complete. Synthetic sequences are optimized with model compound 21 (Scheme 4). Here again, bromination 21 + 23 is quantitative, while two-fold HBr elimination 23 -+ 22 with Et,N proceeds in 51 YO yield. Dibromide 23 easily undergoes HBr elimination followed by a Br shift to give bromide 29. Contrary to cationic polymerization, anionic polymerization of simple pentafulvenes 1 to 2 (which would be attractive in view of the conjugated polymers 3) is not successful: For pentafulvene lb (R = X = MeS), the main reaction is Diels-Alder-type dimerization l b -+ 1% (Scheme 2), even under anionic conditions. 1. Introduction. -Pentafulvenes ( = 5-methylidenecyclopenta-1,3-dienes) 1 are cyclic cross-conjugated molecules with a five-membered ring whose electronic properties are strongly varying with exocyclic substituents [&6] influencing the extent of 71-delocalization as well as the HOMO-LUMO gap. If these substituent effects would be operative in polymers containing pentafulvene-diyl structural units as well, then polymers with considerably varying electronic properties could in principle be available. In fact, semiempirical calculations [7] predict that some types of long-chain polyenes with fulvene-diyl or fulvalene-diyl structural units should be characterized by a relatively small energy difference between the HOMO and the LUMO. Therefore, they are very attractive in view of polymers with unique electrical and optical properties. Furthermore, polymers of this type or their dihydro precursors (see Scheme 1 ) should be of interest in view of the synthesis of 'nonclassical non-alternant polymers ' [8].Some synthetic pathways to polymers with pentafulvene-and pentafulvalene-(5-(cyclopenta-2,4-dien-l-ylidene)cyclopenta-1,3-diene)-derived structural units are summarized in Scheme 1. Considering the fact that pentafulvenes 1 are easily attacked by nucleophiles at C(6) to give substituted cyclopentadienides and, after protonation, substituted cyclopentadienes (for examples, see [9-1 l]), anionic polymerization of pentafulvenes 1 to 2 followed by HX elimination (+ 3; Route A ) should be an attractive procedure. On

show abstract

“…Sie wurden durch ihre chemischen Reaktionen charakterisiert, die ganz denen der niedermolekularen Vertreter dieser St~ffklasse~~-') entsprachen: Umsetzung mit Sauerstoff fiihrte zu makromolekularen polyvalenten Alkoholen (2), Umsetzung mit Schwefeldioxyd zu entsprechenden Sulfinsauren (3). und Riickstande IR-spektroskopisch untersucht.…”

Section: Abb 1 Abnahme Der Doppelbindungen In Abhiingigkeit Von Derunclassified

Über anionische pfropfpolymerisationen. 6. Mitt.. Herstellung von makromolekülen mit aluminium‐organischen substituenten und ihre überführung in makromolekulare komplexkatalysatoren zur pfropfpolymerisation von äthylen, propylen und anderen monomeren

Greber

Egle

1963

Makromol. Chem.

View full text Add to dashboard Cite

ZUSAMMENFASSUNG:Durch Addition von Diathylaluminiumhydrid an die seitenkettenstandigen Doppelbindungen von Styrol/Butadien-Copolymeren wurden makromolekulare aluminiumorganische Verbindungen hergestellt und durch typische Reaktionen charakterisiert (Protolyse zu den Hydroderivaten, Oxydation zu Polyhydroxyverbindungen, Umsetzung mit Schwefeldioxyd zu Polysulfinsauren).Mit Verbindungen der fjbergangsmetalle, z. B. TiC14, Tic&, bilden sich makromolekulare ZIEGLER-Katalysatoren, die die Pfropfpolymerisation, z. B. von Athylen, Propylen und Styrol, bei Normaldruck erlauben. Mit Propylen konnte ein Pfropfpolymeres mit isotaktischen Seitenketten isoliert werden. SUMMARY:By addition of diethyl aluminumhydride to the vinyl type double linkages of styrenebutadiene copolymers high molecular organoaluminum compounds were prepared, which were characterized by typical reactions, such as protolytic cleavage to the hydro derivatives, oxydation to polyhydroxy derivatives, and reactions with sulfur dioxyde to polysulfinic acids.With transition metal compounds, e.g. TiC14, TiC13, high molecular ZIEGLER type catalysts were formed that enabled the graft polymerization p.e. of ethylene, propylene and styrene, a t normal pressures. In the case of propylene a graft polymer with isotactic side cliains could be isolated.

show abstract

Metallorganische Verbindungen XIX: Reaktionen der Aluminium‐ Wasserstoff‐Bindung mit Olefinen

Cited by 184 publications

References 13 publications

Hydrometallation of Unsaturated Compounds

Hydrometallation of Unsaturated Compounds

Synthetic Attempts towards Polymers with Pentafulvene Structural Units

Über anionische pfropfpolymerisationen. 6. Mitt.. Herstellung von makromolekülen mit aluminium‐organischen substituenten und ihre überführung in makromolekulare komplexkatalysatoren zur pfropfpolymerisation von äthylen, propylen und anderen monomeren

Contact Info

Product

Resources

About