Tricarbonylchromium Complexes Research Articles

Arene Chromium Complexes with Functionalized Anellated Rings. Selective Formation of Highly Substituted Polycycles

Tricarbonylchromium complexes of benzocyclobutenone, benzocyclobutene- dione, and 1,3-indandione are readily prepared by hydrolysis of the complexes of the cor- responding acetals. Reduction of the benzocyclobutenone complex gives rise to an oxy- anion-driven ring opening to the corresponding ortho-quinodimethane intermediate, which can be trapped with dienophiles. Addition of 1-ethoxy-1-lithioethene allows a stereoselec- tive ring expansion followed by an anionic ketol rearrangement with complete diastereose- lectivity. Addition of 1-lithio-1-methoxyallene gives rise to a rare anionic 1-vinylcy- clobutenol-cyclohexadienol rearrangement. Diaddition of alkenylmetal reagents at both keto groups in benzoyclobutenedione complexes causes dianionic oxy-Cope rearrangements to occur at -78 °C, which are followed by diastereoselective intramolecular aldol additions. In some cases, a completely regioselective mono hydrolysis of di(enolates) was observed. Dianionic oxy-Cope rearrangements can also be realized with unstrained benzil derivatives giving 1,6-hexanediones and the corresponding aldol adducts. The 1,2,3-indantrione com- plex is obtained by oxidation of the 1,3-indandione complex with dimethyldioxirane in good yield and reacts with its central ketone group in hetero Diels-Alder cycloadditions.

An approach to serrulatane diterpenes via endo-selective conjugate nucleophilic addition to arene-Cr(CO)3 complexes.

[formula: see text] Starting from a nonracemic planar-chiral arene tricarbonyl chromium complex, the serrulatane diterpenoid (+)-20-methoxy-serrulat-14-en-7,8-diol was synthesized in a highly stereoselective fashion. The key step of the synthesis is an endo-selective conjugate nucleophilic addition of lithio-methylphenyl sulfone to a 1-ethylidene-tetralin-Cr(CO)3 derivative. By employing different substrates and nucleophiles it was shown that the surprising and rather general endo selectivity must result from a unique complex induced proximity effect under participation of the Cr(CO)3 moiety.

Effective aromaticity of tricarbonylchromiumbenzene, about 25 enhanced over that of benzene: structural evidence from a complexed benzannulene.

The tricarbonylchromium complex of 2,7-di-tert-butyl-trans-12c,12d-dimethylbenzo[e]dihydropyrene is prepared in 65% yield from the parent annulene. Analysis of the (1)H NMR spectrum leads to coupling constant data and Günther's "Q" value data which unequivocally indicate that the tricarbonylchromiumbenzene moiety behaves like an aromatic system of greater bond fixing ability, aromaticity, than benzene itself; this analysis is supported by X-ray structural data and by the rotational position of the tricarbonyl podal. Analysis of chemical shift data indicates that the tricarbonylchromium benzene moiety has about 25% enhanced "aromaticity" over that of benzene.

Synthesis and Characterization of Chromium Tricarbonyl Complexes of 1-Phenylgermatrane and 1-Phenylazagermatrane. Crystal Structure of [N(CH2CH2O)3GeC6H5]Cr(CO)3

The reaction of 1-phenylgermatrane (1) and 1-phenylazagermatrane (2) with Cr(CO)6 affords chromium tricarbonyl complexes [N(CH2CH2O)3GeC6H5]Cr(CO)3 (6) and [N(CH2- CH2NH)3GeC6H5]Cr(CO)3 (7). In contrast, the same reaction of Cr(CO)6 with 1-(9-anthracenyl) germatrane (3) does not proceed. Composition and structures of the 6 and 7 were established by elemental analyses, 1H and 13C NMR spectroscopy and mass spectrometry. The crystal structure of 6 is reported

Chromium tricarbonyl complexes with biphenylene as η 6 ligand: synthesis, structure, dynamic behaviour in solid state and thermal η 6,η 6-haptotropic rearrangements. Experimental (NMR) and theoretical (DFT) studies

The reaction of biphenylene ( 1) with Cr(CO) 3Py 3/BF 3·OEt 2 at 25 °C gives a mixture of two known isomeric complexes: tricarbonyl(1-4,4a,8b-η 6-biphenylene)chromium ( 2) (yield 62%) and hexacarbonyl(μ-η 6:η 6-biphenylene)bis-chromium ( 3) (yield 4%). Complexes 2 and 3 were separated by thin layer chromatography on silica and characterised by 1H and 13C, as well as 13C CP MAS-NMR. X-ray structure analysis for 3 proved trans-orientation of the chromium tricarbonyl groups. A novel regioselective method for the synthesis of (η 6-biphenylene)chromium tricarbonyl complexes bearing a substituent R (D ( 4), CH 3 ( 5)) in position 1 of the coordinated ring was proposed. The kinetics of η 6,η 6-inter-ring haptotropic rearrangement (IRHR) for 4 in inert, noncoordinating C 6F 6 was investigated by 2H–{ 1H}-NMR spectroscopy. Density function theory (DFT) calculations for ground, intermediate and transition states were done and fitted well with experiment.

Stereocontrolled [3 + 2] Annulations with Arene Chromium Tricarbonyl Complexes: Construction of Spirocyclic Compounds Related to Fredericamycin A

[reaction: see text] An efficient method has been developed for the stereocontrolled construction of polycyclic and spirocyclic compounds, including the spirocyclic core of the antitumor agent fredericamycin A. The strategy involves a one-pot aldol addition/Brook rearrangement/cyclization sequence beginning from arene chromium tricarbonyl complexes and can formally be described as a [3 + 2] annulation.

Application of chiral lithium amide base chemistry to the synthesis of planar chiral (arene)tricarbonylchromium(0) complexes

Asymmetric functionalisation of tricarbonylchromium(0) complexes of benzyl alkyl ethers using a dilithiated chiral amide base is the key step in a short and versatile synthesis of planar chiral (arene)tricarbonylchromium(0) complexes. The synthesis of four complexes of potential use in asymmetric catalysis is described herein together with the first demonstration that the asymmetric functionalisation mediated by this chiral base may be used to introduce phosphine substituents.

Planar chiral (η 6-arene)tricarbonylchromium complexes derived from mandelic acid

The enantiomers of mandelic acid have each been converted into 1,3-dioxolan-4-one derivatives. Formation of the planar chiral (η 6-arene)tricarbonylchromium complexes has enabled an investigation of their potential to promote discrimination between the diastereotopic ortho and/or meta arene hydrogens during lithiation–silylation.

Intermolecular Interactions in (Arene)chromium Carbonyl Compounds: Prediction of Chiral Crystal Packing from Racemate Structure

Six X-ray crystal structures are reported, all containing substituted triphenylmethanol derivative 4 either alone or as its mono or bis(chromium tricarbonyl) complexes. All four chromium complexes studied crystallize with two independent molecules in the crystallographic asymmetric unit. It is demonstrated that from the X-ray crystal structure of the acentric racemic (+/-)-(1pR,1' 'R)(1pS,1' 'S)-[Cr(CO)(3)(eta(6)-t-BuC(6)H(3)(CMeOMe)CPh(2)OH)], (+/-)-3, it is possible to deduce the 4-fold helical structure of the chiral (-)-(1pR,1' 'R) isomer, (-)-3. The bimetallic derivatives demonstrate the ability to control intermolecular interactions by the positioning of relative stereochemistry.

ChemInform Abstract: Synthesis of η6‐ (4a‐Methyl‐1,2,3,4‐tetrahydro‐4aH‐carbazole)tricarbonylchromium Complex and Stereoelectronic Behavior with Organolithium Reagents: An Apparent Frontal Attack to the (CO)3Cr Group.

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Asymmetric synthesis of axially chiral benzamides and anilides by enantiotopic lithiation of prochiral arene chromium complexes.

Axially chiral benzamides and anilides were prepared by enantiotopic lithiation at the distinguished benzylic methyl of prochiral tricarbonylchromium complexes of N,N-diethyl 2,6-dimethylbenzamide (1) and N-methyl-N-acyl 2,6-dimethylaniline (14 and 21) with a chiral lithium amide base followed by electrophilic substitution in good yields with high optical purity. The resulting axially chiral chromium-complexed benzamides and anilides were oxidized under air to give chromium-free axially chiral benzamides and anilides in an enantiomerically active form without axial bond rotation at room temperature.

Endo-Selective allylation at the benzylic centre of a Cr(CO)3 complexed aromatic ring

In the presence of TiCl4, allyllithium adds to tricarbonylchromium complexes of 2-arylidene-1-tetralone and 2-arylideneindan-1-one (1a–c) to afford endo-1,2-adducts (2a–c) exclusively. Subsequent oxy-Cope rearrangement delivers the allyl group stereospecifically along the endo-face to the sterically hindered benzylic position of the metal-complexed ring.

Synthesis and biological evaluation of new antimalarial isonitriles related to marine diterpenoids

By exploiting the chemistry of arene tricarbonylchromium(0) complexes, some analogues of antimalarial marine isonitrile diterpenoids were synthesized in a completely diastereoselective fashion and their activity against the malaria parasite Plasmodium falciparum was assessed in an in vitro assay.

Nucleophilic addition reactions of bridged triene η6-chromiumtricarbonyl complexes

The metal-mediated addition of a range of nucleophiles to several bridged η6-chromiumtricarbonyl complexes has been demonstrated for the first time. The reaction proceeds in regio- and stereoselective fashion and in fair to good yield. The new reaction was applied to the synthesis of an advanced intermediate towards anatoxin-a.

High-resolution and cross-polarization magic angle spinning NMR studies of tricarbonylchromium complexes with polycyclic aromatic ligands

The strategy of investigation of the structures and transformations of organometallic compounds by high-resolution NMR spectroscopy in solutions and in the solid state (cross-polarization magic angle spinning NMR) was considered in relation to tricarbonylchromium complexes with polycyclic aromatic ligands.

Triarylation of eta 6-dihydronaphthalene-Cr(CO)3 complexes.

With ease, eta 6-dihydronaphthalene tricarbonylchromium(0) complexes undergo a triple arylation with concomitant ring closure, when submitted to Heck reactions under 'Jeffery conditions'.

η 6-Arene–tricarbonylchromium complexes in the syntheses of trans-resveratrol and pinostilbene

New syntheses of trans-resveratrol (trans-3,5,4'-trihydroxystilbene) and pinostilbene (trans-3,4'-dihydroxy-5-methoxystilbene) via nucleophilic demethylation of trimethoxystilbene were performed, whereby trans-3,5,4'-trimethoxystilbene was obtained through facilitated benzylic deprotonation of an η6-benzene-Cr(CO)3 derivative and subsequent coupling with para-anisaldehyde in an aldol-type or Wittig–Horner reaction.

Synthesis of Tricarbonyl(diacetylarene)chromium and Tricarbonyl(diformylarene)chromium Complexes

Tricarbonylchromium complexes of diacetylbenzenes and 2,2'-diacetylbiphenyl were prepared in reasonable yields by direct complexation of the starting materials. Tricarbonylchromium complexes of diformylbenzenes and 2,2'-diformylbiphenyl were prepared in good yields by the complexation of the corresponding dioxolanes followed by acidic hydrolysis of the protective groups.

Electron Transfer Driven Transformations of Transition Metal π-Complexes: Samarium(II) Iodide Mediated Coupling of Fluoroarene-Cr(CO)3Complexes with Ketones

Fluoro-substituted η 6 -arene tricarbonylchromium complexes react with aliphatic ketones in the presence of SmI 2 and tBuOH under C-C bond formation to give the corresponding tertiary benzylic alcohols in up to 77% yield. Chlorobenzene-Cr(CO) 3 exhibit a similar reactivity. The reactions proceed through attack of a ketyl radical to the complexed arene followed by single electron reduction of the 17 VE intermediate. The overall reaction parallels a nucleophilic aromatic substitution of fluoride (S N Ar) and preferentially occurs in a meta-tele fashion.

α-Arylation of 2-Arylacetates and Benzofuran-2-one with Tricarbonyl(fluoroarene)chromium Complexes

In order to synthesise fragments of the natural product diazonamide A, α-arylation of 2-arylacetates 3 and benzofuran-2-one with the aid of the tricarbonyl(fluoroarene)chromium complex rac-2 was investigated. After decomplexation of the products rac-4 and rac-6, it was possible to obtain 2,2-diarylacetates rac-5 and the 3-arylbenzofuran-2-one rac-7.