143063-47-2Relevant academic research and scientific papers
Alkoxy-substituted group 6 allenylidene complexes - Synthesis and properties
Szesni, Normen,Weibert, Bernhard,Fischer, Helmut
, p. 617 - 632 (2006)
Bis(alkoxy)allenylidene complexes, [(CO)5MCCC(OR′)OR], as well as mono(alkoxy)allenylidene complexes, [(CO)5MCCC(OR′)Ph], of chromium and tungsten are accessible from propynones [HCCC(O)Ph] or propynoic acid esters [HCCC(O)OR; R = Et, (-)-menthyl, endo-bornyl] by the following reaction sequence: (a) deprotonation of the alkynes, (b) reaction with [(CO)5M-THF] (M = Cr, W), and (c) alkylation of the resulting alkynyl metallate, [(CO)5MCCC(O)R], with Meerwein salts. Vinylidene complexes, [(CO)5MCC(R′)C(O)OR], are formed as a by-product by Cβ-alkylation of the alkynyl metallate. Dimethylamine displaces one alkoxy substituent of the bis(alkoxy)allenylidene complexes to give dimethylamino(alkoxy)allenylidene complexes, [(CO)5MCCC(OR)NMe 2]. The analogous reaction of dimethylamine with a mono(alkoxy)-substituted allenylidene complex affords the aminoallenylidene complex [(CO)5CrCCC(NMe2)Ph]. When the amine is used in large excess, the α,β-unsaturated aminocarbene complex [(CO) 5CrC(NMe2)C(H)C(NMe2)Ph] is additionally formed by addition of the amine across the CαCβ-bond of the allenylidene ligand. The reaction of [(CO)5MCCC(OEt) 2] with dimethyl ethylenediamine offers access to bis(amino)allenylidene complexes, in which Cγ is part of a five-membered heterocycle. Photolysis of bis(alkoxy)allenylidene complexes in the presence of triphenylphosphine yields tetracarbonyl- and tricarbonyl{bis(phosphine)}allenylidene complexes. Diethylaminopropyne inserts into the CβCγ bond of [(CO) 5MCCC(OEt)OMethyl] to give alkenylallenylidene complexes. Subsequent acid-catalyzed intramolecular cyclization affords a pyranylidene complex.
Organic Syntheses via Transition Metal Complexes, 62. - First Carbene Complexes (M = Cr, W) with Carbohydrate Substituents
Aumann, Rudolf
, p. 2773 - 2778 (2007/10/02)
The first examples of transition metal carbene complexes of carbohydrate derivatives are described: 1,2:5,6-Di-O-isopropylidene-α-D-glucofuranose (2a), 1,2:5,6-di-O-isopropylidene-α-D-allofuranose (2b), and 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose (2c) add regiospecifically at C-3 of alkynylcarbene complexes LnM=C(OEt)-C=-CPh 1 nM = Cr(CO)5 (a), W(CO)5 (b) to give vinylcarbene complexes LnM=C(OEt)-CH=C(Ph)-O(sugar) (E/Z)-3a - g in good to excellent yields.As a minor side reaction the alkynyl carbene complex (CO)5W=C(OEt)-C=-CPh (b) isomerises to give the 1,2-propadienylidene complex (CO)5W=C=C=C(OEt)C6H5 (4b). Key Words: Carbene complexes of carbohydrate derivatives / Vinylcarbene chromium and tungsten complexes / α-D-Mannofuranosides, 2,3:5,6-di-O-isopropylidene-, of carbene complexes / α-D-Allofuranosides, 1,2:5,6-di-O-isopropylidene-, of carbene complexes / α-D-Glucofuranosides, 1,2:5,6-di-O-isopropylidene-, of carbene complexes / 1,2-Propadienyliden tungsten complex
