Arene Tricarbonylchromium Complexes Research Articles

Asymmetric synthesis of a fully protected ent-actinoidinic acid.

[structure: see text] The asymmetric synthesis of a fully protected ent-actinoidinic acid derivative 14 is described. As key steps, an enantioselective deprotonation of an arene tricarbonylchromium(0) complex and a diastereoselective Suzuki coupling were applied. The asymmetric centers of the amino acid function were created via stereocontrolled Strecker reactions.

Contra-intuitive stereocontrol: endo-selective nucleophilic additions on an arene–tricarbonylchromium template

In arene–tricarbonylchromium complexes, exo-selectivity is the normal. This account, on the other hand, summarizes our results of endo-selective nucleophilic additions with very high stereocontrol at relatively remote sites, which enhances the potential of these complexes as synthons for target synthesis.

Intramolecular Pd-catalyzed carbocyclization, Heck reactions, and aryl-radical cyclizations with planar chiral arene tricarbonyl chromium complexes.

(o-butenylhalobenzene)Cr(CO)(3) complexes were synthesized by diastereoselectve allylmetal additions to o-halo benzaldehyde complexes. The addition of allylZnBr proved particularly convenient and clean. The complexes undergo intramolecular Pd-catalyzed cyclizations (Heck reactions) without decomplexation and/or alkene isomerization. In complexes with a benzylic stereogenic center, the diastereoselectivity of the alkene carbopalladation is governed by the planar chirality of the complex rather than by the benzylic stereogenic center in the side chain. This reaction outcome can be rationalized by the geometry of the arene plane vs that of the Pd coordination plane in the transition step of the alkene carbopalladation step. An alternative cyclization procedure involves the generation of a Cr(CO)(3)-coordinated arene radical from the bromo and iodo complexes. Intramolecular aryl-radical cyclization affords indan complexes. The transition metal arene pi-bond remains intact during this process.

Reversal of Asymmetric Induction in Arenetricarbonyl-chromium(0) Complexes via Dilithiation with the (-)-Sparteine/BuLi System and Enantioselective Quench

Reversal of Asymmetric Induction in Arenetricarbonyl-chromium(0) Complexes via Dilithiation with the (-)-Sparteine/BuLi System and Enantioselective Quench

Diastereoselective Transformation of Arenes into Highly Enantiomerically Enriched Substituted Cyclohexadienes

Sequential addition of a C-nucleophile and a C-electrophile to enantiomerically pure arene tricarbonyl chromium complexes 3a,b, 6, and 8b, containing aryl bound chiral oxazoline, SAMP-hydrazone and chiral imine auxiliaries affording substituted cyclohexadienes. C-Nucleophiles included alkyl-, vinyl-, and phenyl-lithium reagents. C-Electrophiles included methyl iodide, allyl bromide, benzyl bromide, and propargyl bromides. The 1,3-cylohexadienes were obtained with a 1,5,6-substitution pattern. The results are consistent with a diastereoselective exo-nucleophilic addition to an ortho position of the complexed arene, followed by addition of the electrophile to the metal center. With allyl, ben-zyl, and propargyl groups, direct reductive elimination then yielded trans-5,6-substituted products. With methyl iodide, reductive elimination was preceded by CO insertion and acetyl cyclohexadienes were formed exclusively whose in situ deprotonation/alkylation gave products in which three C-substituents had been added across an arene double bond with complete regio- and stereocontrol. The two path-ways reflect migratory aptitude to carbonylation. An X-ray structure determination of the phenyl oxazoline complex 3a allowed a rationalization of observed diastereoselectivity. Asymmetric induction was very high with the oxazoline and the SAMP-hydrazone complexes (>90% de) whereas the chiral benzaldehyde imine complex 8b afforded the substituted diene aldehydes in moderate enantiomeric purity (34-58% ee). Changing the reaction medium from THF to toluene in reactions with 8b resulted in products of the opposite chirality.

Asymmetric deprotonation—substitution of arenetricarbonylchromium(0) complexes: substituent controlled lithiation with the butyllithium–sparteine system

Attempted enantioselective deprotonation of fluorobenzenetricarbonylchromium(0) with ca. 1 equivalent of butyllithium/(−)-sparteine in ether–hexane at −78°C followed by a chlorotrimethylsilane quench gave the racemic ortho-substituted product. Analogous enantioselective deprotonation of anisoletricarbonylchromium(0), followed by electrophilic quench, gave the 1-(Rp)-substituted complexes in up to 77% yield with 27% e.e., but with methoxymethoxybenzenetricarbonylchromium(0), (4-triisopropylsilyloxymethyl)methoxymethoxybenzenetricarbonylchromium(0) and (N-t-butoxycarbonylaniline)tricarbonylchromium(0), the 1-(Sp)-products were formed in up to 58% yield with 92% e.e. The results are explained in terms of coordinative and non-coordinative enantioselective lithiation.

The first examples of ester enolate addition across a chiral (alkoxybenzene)–chromium complex π-bond with a remarkable degree of 1,5-asymmetric induction

The first examples are described wherein addition of an ester enolate to an alkoxy-substituted arene–chromium tricarbonyl complex, to afford a substituted cyclohexenone in high enantiomeric excess.

Directed Lithiation in Arenetricarbonylchromium(0) Complexes: Assessment of Some Directing Group Specificities and of Electrophilic Quench Efficacies

The synthesis of a series of phenol ethers and 4-triisopropylsilyloxymethylphenol ethers and their η 6-tricarbonylchromium(0) complexes are reported. The directed lithiation of these followed by quenching with a series of electrophiles gave access to a wide range of functionalised complexes for use in synthesis.

Single versus double nucleophilic addition of carboxylic acid enolates to anisole tricarbonyl chromium complexes with formation of arylcarboxylic acids and/or tetrahydrobenzofuran-2,5-diones: the size of the substituents on the acid makes the difference

Potassium enolates of carboxylic acid trimethylsilyl esters, obtained upon interaction of bis(trimethylsilyl)ketene acetals with t -BuOK, react with anisole tricarbonyl chromium to give, directly upon iodine promoted oxidative demetalation, a mixture of the expected carboxylic acids and of bicyclic lactones resulting, on a formal point of view, from a double nucleophilic addition of the dianions of the carboxylic acids to the arene complexes followed by hydrolysis of labile dienol ethers. The course of the reaction was highly dependent on the nature of the starting carboxylic acid: enolates resulting from sterically crowded carboxylic acids led in preference to the lactones, whereas those originating from non-hindered acids gave mostly arylcarboxylic acids. The structures of two of these lactones have been established by X-ray diffraction studies. An intermediate dienol ether originating from the 1,2 addition of t -butyl acetic acid dianion to a double bond of anisole could be isolated and fully characterized by NMR spectroscopy. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS arene–tricarbonyl–chromium complexes / bis(trimethylsilyl)ketene acetals / arylcarboxylic acids / tetrahydrobenzofuran-2,5-diones Version française abrégée — Additions nucléophiles d’énolates d’acides carboxyliques à l’anisoletricarbonylchrome : influence de la taille des substituants de l’acide sur la formation d’acides arylcarboxyliques et (ou) de tetrahydrobenzofurane-2,5-diones. L’interaction de solution de t butylate de potassium dans le THF avec les acétals de cétènes disilylés conduit de façon quantitative aux énolates d’esters correspondants. Ces derniers réagissent, par exemple, avec les aldéhydes pour donner des β-hydroxyacides, mais également avec les complexes arène–chrome–tricarbonyle pour conduire, après démétallation oxydante, à des acides arylcarboxyliques. Dans le cas du complexe de l’anisole, des lactones bicycliques, provenant formellement d’une double addition nucléophile des dianions des acides carboxyliques à une double liaison du cycle aromatique, suivie de l’hydrolyse d’un éther de diénol intermédiaire, sont isolées à côté des acides arylcarboxyliques attendus. Le rapport acide/lactone dépend de la nature des substituants des cétals de cétènes, les cétals fortement encombrés conduisant préférentiellement aux lactones. La structure de deux de ces lactones bicycliques a été établie par diffraction des rayons X. Par ailleurs, un intermédiaire réactionnel, un éther de diénol provenant d’une addition 1,2 de l’anion de l’acide t -butylacétique à une double liaison de l’anisole, a été isolé et caractérisé. Un mécanisme faisant intervenir deux additions nucléophiles successives est proposé : une première addition nucléophile de l’énolate sur les complexes de départ crée une liaison carbone–carbone. Elle est suivie de l’oxydation du chrome par l’iode et d’une deuxième addition nucléophile, mettant en jeu l’oxygène du groupement carboxyle, avec création d’une liaison carbone–oxygène. L’ensemble de ces réactions conduit à une nouvelle molécule, contenant une lactone et un éther de diénol. L’hydrolyse de cette dernière fonction conduit à une tétrahydrobenzofurane-2,5-dione.

Stereoselective bis-functionalizations of arene chromium tricarbonyl complexes via brook rearrangements

[reaction: see text] An efficient method has been developed for the stereoselective bis-functionalization of arene chromium tricarbonyl complexes. Initial nucleophilic addition of organolithium reagents to a carbonyl moiety is followed by a 1,4-carbon to oxygen silyl migration (Brook rearrangement) and alkylation of the resultant aryl anion.

Stereoselective route to mitosanes via tricarbonyl η 6 arene chromium complexes

Stereoselective reduction followed by metalation of a η 6 arene chromium tricarbonyl complex allows rapid access to substituted mitosanes, whose skeleton mimics the mitomycin family of antitumour agents.

Stereoselective reactivity of diastereotopic carbon–carbon triple bonds induced by chiral orthosubstituted arene tricarbonyl chromium complexes. Diastereoselective Co 2(CO) 8 complexation and LiAlH 4 reduction

The diastereoselective Co 2(CO) 8 complexation and LiAlH 4 reduction of diastereotopic carbon–carbon triple bond, induced by chiral ortho substituted arene tricarbonylchromium complexes is described. The relative configuration of the obtained diastereoisomers are determined unequivocally by X-ray crystallography, 1H-NMR and transition state analysis.

ChemInform Abstract: Dipolar [3 + 2] Cycloaddition Reactions with Planar Chiral Arene Tricarbonyl Chromium Complexes: Synthesis of Enantiopure Trisubstituted Pyrrolidines.

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Molecular modelling of ( η6-arene)–Cr(CO) 3 complex systems : The barrier to rotation about the arene–metal bond axis

Based on the 1H-NMR calculated percentage of population of mono- and disubstituted arene–tricarbonyl–chromium complexes, the preferred conformation with regard to the internal rotation about the arene–chromium axis has been theoretically studied. Analytical force field expressions have also been developed to calculate the arene–(CO) 3 potential barrier and arene–Cr bond stretching. The torsional and stretching force constants are given. The new expressions to calculate force field were derived from reactivity constants and vibrational spectroscopy. The arene–Cr(CO) 3 intermolecular forces which are responsible for the change in equilibrium ratio of stable conformations were divided into two terms, the potential barrier of the arene–(CO) 3 rotating groups, and the arene–chromium stretching energy. The stable forms determined by these forces can be changed by great attractive and/or repulsive electrostatic and steric non-bonded interactions. These non-bonded forces are also depending on the arene–metal distance, which change linearly following the resonance effect of substituents on the aromatic ring. Arene–chromium bonding forces play the most important role in the arene–tricarbonyl–chromium studied here. There are appreciable changes in the arene–chromium distances from one complex to another, and it was found to be dependent of electron density on the aromatic ring. Electron-donating or electron-withdrawing substituent characters affect directly this distance and the energy difference between stable forms.

Conformational searching using the comparative molecular field analysis (CoMFA) method of substituted arene–tricarbonyl–chromium complexes

This article deals with the ( η 6-arene)–Cr(CO) 3 interaction study. A new strategy developed using the comparative molecular field analysis (CoMFA) method has been developed. It consists of the arene–(CO) 3 rotational barrier determination, which was determined from the partial least squares regression coefficients. The 1H-NMR calculated percentage of population of the eclipsed forms of 22 complexes has been used in this correlation. These NMR data will be discussed on the basis of the classical QSAR and 3D-QSAR. The goal of this study is to show the possibility of using the CoMFA method as a force field tool development.

Dipolar [3+2] Cycloaddition Reactions with Planar Chiral Arene Tricarbonyl Chromium Complexes: Synthesis of Enantiopure Trisubstituted Pyrrolidines

Dipolar [3+2] Cycloaddition Reactions with Planar Chiral Arene Tricarbonyl Chromium Complexes: Synthesis of Enantiopure Trisubstituted Pyrrolidines

Sidechain Functionalizations by Cuprate Additions to Phosphorylallenyl-Substituted Arenetricarbonylchromium Complexes

Sidechain Functionalizations by Cuprate Additions to Phosphorylallenyl-Substituted Arenetricarbonylchromium Complexes

Asymmetric synthesis of sulfinyl-substituted arene chromium tricarbonyl complexes

The synthesis of (SRSS)-[(phenylsulfinyl)benzene] chromium tricarbonyl 5 and (SRSS)-[(p-tolylsulfinyl)benzene] chromium tricarbonyl 6 is achieved via a nucleophilic displacement reaction between the anion derived from (benzene) chromium tricarbonyl 9 and a suitable sulfinate ester. Replacing the sulfinate ester with a chiral sulfinyl-transfer reagent allows the isolation of the non-racemic sulfinyl-substituted complexes with good enantioselectivities (ee 80–89%) under optimised conditions. The use of Kagan’s cyclic sulfite methodology for the synthesis of an enantiomerically pure tert-butylsulfinyl complex is unsuccessful, but results in the identification of a novel fragmentation–isomerisation process of the intermediate sulfinate.

Unexpected formation of 3,3a,4,7a-tetrahydrobenzofuran-2,5-diones as well as arene carboxylic acids upon formal double exo nucleophilic addition of R1R2C−COO− to anisolechromium tricarbonyl complexes

Bis(trimethylsily)ketene acetals of the general structure 2 (R1 = H, Me, R2 = Me, Et, Pri, CMe=CH2) react at –78 °C in the presence of ButOK with a series of arenechromium tricarbonyl complexes 3 to give as expected, after oxidation with I2 followed by silica gel chromatography, arylcarboxylic acids 7. In the case of anisolechromium tricarbonyl 8, besides the m-methoxyarylcarboxylic acids, tetrahydrobenzofuran-2,5-diones 11, are formed as the result of a double nucleophilic addition.

(η 6-Arene)tricarbonylchromium and (η 5-cyclohexadienyl) tricarbonylmanganese complexes: indirect nucleophilic substitutions

Treatment of X-substituted (η 6-arene)tricarbonylchromium complexes with a nucleophile and a proton source afforded new arenetricarbonylchromium complexes via chromium hydride intermediates and elimination of HX ( cine and tele nucleophilic aromatic substitutions). Treatment of (η 5-X-substituted-cyclohexadienyl)tricarbonyl manganese complexes with hydride and a proton source gave η 5-cyclohexadienyl complexes resulting from a cleavage of the C–X bond: the η 3-X-substituted cyclohexenyl intermediates underwent elimination of an agostic hydrogen and the X group.