Diastereotopic group selectivity in the deprotonation of (.eta.-arene)Cr(CO)3 complexes

Heppert, Joseph A.; Thomas-Miller, M. Elizabeth.; Milligan, Michael L.; Velde, David Vander; Aubé, Jeffrey

doi:10.1021/om00102a032

Cited by 17 publications

(7 citation statements)

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“…12). (47,214) With tricarbonyl(benzaldimine)chromium, deprotonation takes place at the benzylic position, and the enantiopure ortho-substituted analog 135 gives optically pure --substituted benzylamine derivatives upon trapping with alkyl halides and subsequent hydrolysis (Eq. 124).…”

Section: --Heteroatom-substituted Tricarbonyl(arene)chromium Complexesmentioning

confidence: 99%

“…In parallel with reactions involving the generation of metal enolates from stannylated or silylated precursors, there have been recent developments on the use of ketones that undergo in situ enolization or activation by transient conversion into enamines and participate in aldol addition reactions. (214) In the first of these, lanthanum binaphthoxide complexes (LLB) are able to effect deprotonation of ketones and activation of aldehydes to afford aldol adducts in high selectivities and yields (Eqs. 45 and 46).…”

Section: Direct Aldol Addition Reactions Of Unsubstituted Systemsmentioning

confidence: 99%

“…22). (83,213,214) (110) (111) The ligands are derived from linked BINOL or bisprolinols anchored around a phenol. The typical addition reactions are conducted at reduced temperature and provide adducts in impressive levels of selectivity.…”

Section: Direct Aldol Addition Reactions Of Substituted Systemsmentioning

confidence: 99%

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

Uemura

2006

Organic Reactions

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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.

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Section: --Heteroatom-substituted Tricarbonyl(arene)chromium Complexesmentioning

confidence: 99%

Section: Direct Aldol Addition Reactions Of Unsubstituted Systemsmentioning

confidence: 99%

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

Uemura

2006

Organic Reactions

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“…This may be achieved by ortho ‐deprotonation,7 either by a chiral base8 or by an achiral base on an (arene)tricarbonylchromium complex bearing a chiral auxiliary 9. Among others, chiral acetals9b–9h and chiral aminals9k,9l have already been used for this purpose. However, chiral acetals have the drawback of a difficult hydrolysis,9c–9g whereas chiral aminals have the drawback of a sometimes moderate ortho regioselectivity 9k…”

Section: Introductionmentioning

confidence: 99%

Diastereoselective Alkylation of (Arene)tricarbonylchromium and Ferrocene Complexes Using a Chiral, C₂‐Symmetrical 1,2‐Diamine as Auxiliary

et al. 2005

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The aminal of (benzaldehyde)tricarbonylchromium and en‐antiopure bipyrrolidine undergoes diastereoselective ortho‐metallation with butyllithium. Quenching with various electrophiles, followed by hydrolysis of the aminal, affords ortho‐substituted (benzaldehyde)tricarbonylchromium compounds with high ee (91–99 %). When quenched with Ph2PCl, a new chiral P,N‐bidentate ligand is obtained, which shows efficiency in Pd‐ and Cu‐catalysed reactions. The aminal of ferrocenecarbaldehyde could also be formed, but the ortho‐deprotonation occurs with only moderate diastereoselectivity (70 %). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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“…The planar chirality of the (h 6 -arene)chromium moiety is deduced to be R from diastereoselective ortho-lithiation of 3 as reported in the literature. [23][24][25][26] Although most of the phosphorus(III) compounds are known to be susceptible to air oxidation, the stibanes 2 and 4 are isolated as relatively stable crystals in air. The structures of 2 and 4 were elucidated mainly by their MS, 1 H-NMR, and elemental analyses.…”

Section: )mentioning

confidence: 99%

Synthesis of Optically Active Organoantimony Compounds Having an (S)-.ALPHA.-Methylbenzyldimethylamine Group and Its Evaluation for Asymmetric Reaction.

Yasuike

Okajima

Kurita

2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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The chemistry of asymmetric catalysts is an interesting research field in asymmetric reactions and has recently been the focus of attention.1) A number of chiral ligands containing nitrogen, 2) phosphorus [3][4][5][6][7][8][9] and arsenic [10][11][12][13] have been widely studied and are well documented. With respect to enantiomerically pure phosphine ligands bearing a chiral benzylamine moiety, (R/S)-[a-methyl-2-(diphenylphosphino)-benzyl]dimethylamine (AMPhos) [14][15][16][17] and its (h 6 -arene)-chromium complex 18,19) have been reported to be effective chiral ligands for enantioselective reductions, cross-coupling reactions, and allylic alkylations. It is also known that a variety of optically active phosphine derivatives bearing a ferrocene skeleton can be used in a wide range of asymmetric reactions.7) However, the synthesis of optically active organoantimony compounds and its applications to asymmetric reactions have not been reported so far. In this context, we are interested in the synthesis and utilization of optically active organoantimony compounds for asymmetric synthesis and have recently reported an efficient and stereoselective resolution of racemic Sb-chiral stibindoles 20) and 2,2Ј-bis[di(p-tolyl)stibano]-1,1Ј-binaphthyls (BINASb).21) Here we report the syntheses of new, optically active antimony compounds having a C-chiral benzylamine moiety, (S)-(amethyl-2-di-p-tolylstibanobenzyl)dimethylamine [AMSb] (2) and AMSb-Cr(CO) 3 complex (4), and their use for transition metal-catalyzed enantioselective hydrosilylation of ketones.The syntheses of the optically pure organoantimony compounds 2 and 4 used in this study are shown in Chart 1. (S)-(a-Methylbenzyl)dimethylamine (1) was ortho-lithiated with n-butyllithium (n-BuLi) in ether according to the literature method, 17) followed by trapping with bromodi(p-tolyl)stibane [(p-Tol) 2 SbBr] to give AMSb (2) in 45% yield; [a] D ϩ12.6°( cϭ2, CHCl 3 ). On the other hand, (h 6 -arene)chromium complexes have some significant properties owing to the strong electron-withdrawing ability and steric bulkiness of the coordinated transition metal, and their applications to organic synthesis have been developed.22) It is also known that the arylic hydrogens on the chromium complexes are easily lithiated to functionalize at an appropriate position. The key common starting (S)-tricarbony[h 6 -(a-methylbenzyl)dimethylamine]chromium (3) was obtained by the reaction of 1 with hexacarbonylchromium in 73% yield as yellow crystals. 23)The novel chiral antimony compound 4 was readily prepared by way of diastereoselective lithiation of 3. According to the procedure reported by Gibson and co-workers, 24) the chromium complex 3 was lithiated by treatment with tertbutyllithium (t-BuLi) in anhydrous diethyl ether at Ϫ80°C under an argon atmosphere. Subsequent treatment of the mixture with (p-Tol) 2 SbBr at the same temperature gave rise to CHCl 3 ) as the sole product. The planar chirality of the (h 6 -arene)chromium moiety is deduced to be R from diastereoselective ortho-lithi...

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Diastereotopic group selectivity in the deprotonation of (.eta.-arene)Cr(CO)3 complexes

Cited by 17 publications

References 0 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

Diastereoselective Alkylation of (Arene)tricarbonylchromium and Ferrocene Complexes Using a Chiral, C₂‐Symmetrical 1,2‐Diamine as Auxiliary

Synthesis of Optically Active Organoantimony Compounds Having an (S)-.ALPHA.-Methylbenzyldimethylamine Group and Its Evaluation for Asymmetric Reaction.

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Diastereotopic group selectivity in the deprotonation of (.eta.-arene)Cr(CO)3 complexes

Cited by 17 publications

References 0 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

Diastereoselective Alkylation of (Arene)tricarbonylchromium and Ferrocene Complexes Using a Chiral, C2‐Symmetrical 1,2‐Diamine as Auxiliary

Synthesis of Optically Active Organoantimony Compounds Having an (S)-.ALPHA.-Methylbenzyldimethylamine Group and Its Evaluation for Asymmetric Reaction.

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Diastereoselective Alkylation of (Arene)tricarbonylchromium and Ferrocene Complexes Using a Chiral, C₂‐Symmetrical 1,2‐Diamine as Auxiliary