Karl Heinz Dötz

Carbene complexes in intramolecular Diels-Alder reactions

Abstract Diene-dienophile functionalized Fischer type carbene complexes [(CO)5W=C(R)]R]are accessible from hexacarbonyl tungsten by a tandem nucleophilic addition/ substitution sequence. Either the diene or the dienophile functionality can be bonded directly to the carbene carbon atom. The synthetic potential of these complexes is demonstrated by furfurylamino(prop-2-enyl)-carbene and diallylamino(furyl) carbene complexes 2 and 11 which - in contrast to their amide analogues - under-go an intramolecular [4+2]cycloaddition under mild conditions. The cycloaddition occurs in a trans mode as is established by X-ray analyses.

Phosphahydroquinones and oxaphospholes via carbene annulation and cycloaddition reactions of chromium carbonyl carbene complexes and phosphaalkynes

Abstract Fischer-type alkoxy(aryl or vinyl)carbene complexes of chromium undergo regiospecific carbene annulation and cycloaddition upon reaction with tert.butyl phosphaacetylene to give highly substituted phosphahydroquinones and/or oxaphospholes. The product distribution is governed by steric and electronic effects arising from the substitution pattern in the carbene ligand. The phosphaannulation products such as phosphabenzene, -naphthalene, -benzofuran, -benzothiophene and -phenanthrene skeletons as well as the 1,3-oxaphospholes are obtained in yields up to 89% and - in part - are characterized by X-ray diffraction.

Reaktionen von Komplexliganden. XXXIV: Tetracarbonyl-Carben-Chelatkomplexe des Chroms, Molybdäns und Wolframs

Abstract The tetracarbonyl[methoxy-2-phenyl(methoxy)carbene- C,O ] and the tetracarbonyl[methoxy(methylmercapto-2-phenyl)carbene- C,S, ] complexes of chromium, molybdenum and tungsten can be made by decarbonylation of the parent pentacarbonyl carbene complexes. The tetracarbonyl compounds have cis configuration and contain a five-membered, almost planar chelate ring which, in the case of the C,O -complexes, is characterized by a long oxygen-to-chromium bond; by contrast, the thio homologue has an envelope conformation.

Reaktionen von komplexliganden: LII . Sechsgliedrige aminocarben-chelatkomplexe: Synthese, alkin / carben-verknüpfung und carbenanellierung

Abstract The photoinduced decarbonylation of pentacarbonyl[(2- N , N -dimethylamino)anilino(phenyl resp. 4-methylphenyl)carbene]chromium ( 1 , 2 ) leads to the formation of the tetracarbonyl carbene( C , N ) complexes 3 and 4 which contain a six-membered chelate ring. These complexes react with internal alkynes to give either the tetracarbonyl(iminoindane- N , N ) chelates 5 and 6 or the tricarbonyl(iminoindane) and -(aminoindene) complexes 7–10 , respectively, depending on the solvent used. An X-ray diffraction study of 6 reveals a relative trans stereochemistry of the former alkyne substituents in the indane skeleton, an envelope conformation of the five-membered chelate ring and a Z -configuration within the imine ligand. Cleaving off the metal, under atmospheric pressure of CO, affords a mixture of iminoindane 12 and aminoindene 13 . Unlike internal alkynes, terminal alkynes react with 3 to give the tetracarbonyl[azabutadiene( N , N )] chelate complexes 14 and 15 .

Reaktionen von Komplexliganden: XLI. Thiocarbenkomplexe des Chroms und Wolframs: Vereinfachte Darstellung, Insertions- und anellierungsreaktionen☆☆☆

Abstract A series of novel thiocarbene complexes of chromium (I-XII) have been obtained in good yields in a one-pot reaction via acetylation of the lithium acylmetallates B in the presence of TMEDA and subsequent thiolysis. The photochemical decarbonylation of ortho -thioanisylcarbene complexes III, VIII and IX leads to cis -tetracarbonylcarbene-(C,S)-chelate complexes XIV-XVI. Carbene annulation of II with 1-hexyne yields naphthol XVII. The pentacarbonyl complexes (with the exception of ortho -substituted aryl compounds) react with 1-diethylaminopropyne to give the pentacarbonyl(diethylamino- E -vinylcarbene) complexes XVIII-XXIII via a highly stereoselective insertioin of the alkyne into the metalue5f8carbene bond.

Reaktionen von Komplexliganden: XLIV. Tetracarbonyl-Aminocarben-Komplexe des Chroms: Synthese und Anellierung zu koordinierten Iminoindanen

Abstract The aminolysis of cis-tetracarbonyl[methoxy(1-methoxy-2-phenyl)carbene]chromium(0) leads to the corresponding aminocarbene chelate complexes. In addition, cis-tetracarbonyl(amine)carbene complexes are formed resulting from ring opening. The product distribution is found to correlate with the basicity of the amine used. Both types of aminocarbene complexes react with alkynes such as butyne-2 to give metal-stabilized iminoindanes.

Reaktionen von Komplexliganden: XLII. Darstellung von Naphthochinonen und Indanonen durch Carbenanellierung an einem Molybdän-Templat☆

Zusammenfassung Pentacarbonyl[methoxy(4-methylphenyl)carbene]molybdenum (I) reacts with terminal alkynes to give, after oxidative work-up, naphthoquinones or indanones in good yields.

Reaktionen von komplexliganden: XLVII. Darstellung von pentacarbonyl-(aryl- und heteroarylcarben)-komplexen des molybdäns☆

Abstract Phenyl-, pyrryl-, furyl- and thienyl carbene complexes of molybdenum have been obtained from Mo(CO) 6 by tandem nucleophilic addition/electrophilic alkylation methodology. The novel compounds have been characterized by spectroscopic means. The thermolability, characteristic of alkoxycarbene complexes of molybdenum, can be controlled by the substitution pattern of the aryl carbene substituent revealing both electronic and steric effects.

Reaktionen von komplexliganden: XLVIII. Carben-Liganden in intramolekularen Pauson—Khand-Reaktionen☆

Abstract Pentacarbonyl[diallylamino(phenylethinyl)carbene]tungsten (I) undergoes an intramolecular Pauson—Khand reaction to give II under extraordinarily mild conditions.

Reaktionen von Komplexliganden: XXXI. Tetramethyl(alkyl- bzw. alkenyl)cyclopentadienyl-Komplexe des Molybdäns

Abstract (η 5 -C 5 Me 4 R)Mo(CO) 2 NO complexes (R = Me, Et, 4-butenyl) were prepared from the corresponding sodium cyclopentadienides, molybdenum hexacarbonyl and N -methyl- N -nitroso- p -toluenesulfonamide in moderate to good yields.