Directed regioselective lithiation of (η6-arene) chromium tricarbonyl complexes

Uemura, Mamoru; Take, Kazuhiko; Isobe, Kazuo; Minami, Tatsuya; Hayashi, Yûji

doi:10.1016/s0040-4020(01)91416-4

Cited by 36 publications

(3 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…148). (315,316) (141) (142) (143) (144) (145) An overview of the aldol reaction in its various incarnations reveals an interesting dichotomy in the development of the two general class types for stereocontrol with respect to the family of ketides they provide access to. Thus, although chiral-auxiliary controlled diastereoselective aldol processes that afford syn or anti -substituted -hydroxy carbonyl compounds allow the ready synthesis of propionate fragments, they in general do not work well, with some exceptions (Eqs.…”

Section: Comparison With Other Methodsmentioning

confidence: 99%

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

Uemura

2006

Organic Reactions

Self Cite

View full text Add to dashboard Cite

This chapter covers reactions of ( 6 -arene) chromium complexes that occur in the side chain of arene, and reactions that exhibit stereocontrol as a result of complexation. Reactions that focus on nucleophilic additions to the chromium-coordinated aromatic ring and on directed lithiation of the arene ring are not covered.The tricarbonyl( 6 -arene) complexes are readily prepared by several convenient methods, and these complexes are relatively stable to air and moisture. Most arenes will coordinate to the tricarbonyl fragment. Certain functional groups are incompatible and electron withdrawing groups, such as CHO and CO 2 H, retard complexation. Protection of these functional groups as acetals or esters followed by chromium complexation and hydrolysis procedures give the corresponding tricarbonylchromium complexes of benzaldehyde or benzoic acid in good yields. Electron-donating substituents accelerate the rate of complexation. The chemical consequences of chromium complexation include (1) the activation of the aromatic ring to nucleophilic addition; (2) enhancement of acidity in the side chain; (3) enhancement of the rate of solvolysis in the side chain; (4) enhancement of acidity of aromatic hydrogens: (5) control of reactions by steric effects of the tricarbonylchromium fragment. After the reaction, the tricarbonylchromium fragment can be easily removed by mild oxidation. When the arene ring is disubstituted with different substituents at the ortho and meta positon, the complexes are planar chiral and the substrates are useful for asymmetric synthesis.

show abstract

Section: Comparison With Other Methodsmentioning

confidence: 99%

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

Uemura

2006

Organic Reactions

Self Cite

View full text Add to dashboard Cite

show abstract

“…The final demethylation of X-14881C (34) to the phenolic ochromycinone (35) using aluminum trichloride proceeded without problems (Scheme 9). A related Friedel-Crafts reaction of a carboxylic acid derived from lactone 38 to yield an anthrone 39 was employed by Uemura et al [48,49]. However, a …”

Section: Friedel-crafts Reactionsmentioning

confidence: 99%

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Krohn

Rohr

1997

Topics in Current Chemistry

182

148

View full text Add to dashboard Cite

General and recent aspects of chemical syntheses on angucyclinones and selected related natural products are summarized here. In the first part of this review on angucyclines, the chemical reaction used as a key step for the construction of the angucyclinone frame is discussed. In the second part, new members of the angucycline group of antibiotics, their bioactivity and recent biosynthetic studies including modern aspects of molecular biology (genetics) are reviewed.

show abstract

“…Jaouen examined intramolecular Friedel−Crafts acylation reactions of chiral-complexed β-phenylpropionic acid derivatives leading to diastereomeric indanone complexes and obtained modest levels of selectivity and low yields of products . Uemura used this chemistry to prepare tetralone derivatives in good yields and excellent diastereoselectivity …”

Section: Introductionmentioning

confidence: 99%

Reactivity of (η⁶-Arene)tricarbonylchromium Complexes toward Additions of Anions, Cations, and Radicals

et al. 2001

View full text Add to dashboard Cite

A computational and experimental study of additions of electrophiles, nucleophiles, and radicals to tricarbonylchromium-complexed arenes is reported. Competition between addition to a complexed arene and addition to a noncomplexed arene was tested using 1,1-dideuterio-1-iodo-2-((phenyl)tricarbonylchromium)-2-phenylethane. Reactions under anionic and cationic conditions give exclusive formation of 1,1-dideuterio-1-((phenyl)tricarbonylchromium)-2-phenylethane arising from addition to the complexed arene. Radical conditions (SmI(2)) afford two isomeric products, reflecting a 2:1 preference for radical addition to the noncomplexed arene. In contrast, intermolecular radical addition competition experiments employing ketyl radical addition to benzene and (benzene)tricarbonylchromium show that addition to the complexed aromatic ring is faster than attack on the noncomplexed species by a factor of at least 100,000. Density functional theory calculations using the B3LYP method, employing a LANL2DZ basis set for geometry optimizations and a DZVP2+ basis set for energy calculations, for all three reactive intermediates showed that tricarbonylchromium stabilizes all three types of intermediates. The computational results for anionic addition agree well with established chemistry and provide structural and energetic details as reference points for comparison with the other reactive intermediates. Intermolecular radical addition leads to exclusive reaction on the complexed arene ring as predicted by the computations. The intramolecular radical reaction involves initial addition to the complexed arene ring followed by an equilibrium leading to the observed product distribution due to a high-energy barrier for homolytic cleavage of an exo bond in the intermediate cyclohexadienyl radical complex. Mechanisms are explored for electrophilic addition to complexed arenes. The calculations strongly favor a pathway in which the cation initially adds to the metal center rather than to the arene ring.

show abstract

Directed regioselective lithiation of (η6-arene) chromium tricarbonyl complexes

Cited by 36 publications

References 43 publications

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Reactivity of (η⁶-Arene)tricarbonylchromium Complexes toward Additions of Anions, Cations, and Radicals

Contact Info

Product

Resources

About

Directed regioselective lithiation of (η6-arene) chromium tricarbonyl complexes

Cited by 36 publications

References 43 publications

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Reactivity of (η6-Arene)tricarbonylchromium Complexes toward Additions of Anions, Cations, and Radicals

Contact Info

Product

Resources

About

Reactivity of (η⁶-Arene)tricarbonylchromium Complexes toward Additions of Anions, Cations, and Radicals