Enantioselective Rhodium-Catalyzed Alkylative Desymmetrization of 3,5-Dimethylglutaric Anhydride

A rhodium-catalyzed enantioselective cross-coupling of sp³ organozinc reagents and 3,5-dimethylglutaric anhydride has been developed to afford the corresponding products, syn-deoxypolypropionates, in excellent yields and enantioselectivities. This reaction has been developed so that both commercially available and in situ prepared organozinc reagents are competent coupling partners.

The structural characterization and hydroformylation activity of the tri-rhodium complex [Rh-3(mu(2)-dppm)(2)(mu(2)-CO)(3)(K-1-CO)(3)]BF4

Rh-2(cod)(2)(mu(2)-dppm)(mu(2)-Cl)]BF4 (1) rearranges under carbon monoxide to give [Rh-3(mu(2)-dppm)(2)-(mu(2)-CO)(3)(K-1-CO)(3)]BF4 (2). Complex 2 has been structurally characterized by single crystal X-ray crystallography. The hydroformylation activities of 1 and 2 were compared for substrates styrene and 1-hexene and the activity of 2 found to be unexpectedly high.

Asymmetric rhodium carbene insertion into the Si-H bond: identification of new dirhodium(II) carboxylate catalysts using parallel synthesis techniques

Decomposition of methyl 2-diazophenylacetate in the presence of silanes and a chiral dirhodium(11) catalyst results in Si-H insertion of the intermediate carbenoid with varying degrees of enantioselectivity. New chiral dirhodium(11) carboxylate catalysts were identified using solution phase parallel synthesis techniques. (C) 2003 Elsevier Science Ltd. All rights reserved.

N-H insertion reactions of rhodium carbenoids. Part 2. Preparation of N-substituted amino(phosphoryl)acetates (N-substituted phosphorylglycine esters).

Rhodium(II) acetate-catalyzed reaction of Et 2-diazo-2-diethoxyphosphorylate, EtO2CC(:N2)PO(OEt)2, with carbamates, amides, ureas or anilines gives a range of N-substituted 2-amino-2-diethoxyphosphorylacetates, EtO2CCH(NHR1)PO(OEt)2 (where R1 = Boc, Cbz, acetyl, propionyl, pivaloyl, n-Pr, Ph and substituted Ph groups), by N-H insertion reaction of the intermediate rhodium carbenoid.

N-H insertion reactions of rhodium carbenoids. Part 1. Preparation of  -amino acid and  -aminophosphonic acid derivatives.

Rh(II) acetate-catalyzed decompn. of diazophenylacetates PhC(N2)CO2Me 1 and PhC(N2)CO2R* 3 [R*OH = (-)-borneol, (+)-menthol, (-)-8-phenylmenthol] in the presence of a range of N-H compds. results in an N-H insertion reaction of the intermediate carbenoids and formation of N-substituted phenylglycine derivs. PhCH(NR1R2)CO2Me 2 [R1 = R2 = Et; R1 = 4-MeOC6H4, COCH2CHMe2, CO2CH2Ph, (S)-CH(CO2Me)CH2Ph, (S)-CHMePh, R2 = H; 64-83% yields] and PhCH(NR1R2)CO2R* 4 (R1 = R2 = Et; R1 = COMe, CO2Me, R2 = H; same R*; 37-71% yields). The corresponding reactions of di-Me ?-diazobenzylphosphonate PhC(N2)P(O)(OMe)2 5 with primary amines constitute a simple route to aminophosphonates PhCH(NHR)P(O)(OMe)2 6 (R = COMe, COEt, CO2CH2Ph, CO2CMe3, 4-ClC6H4, 4-MeC6H4, 4-MeOC6H4; 13-96% yields).

Asymmetric rhodium carbenoid insertion into the Si-H bond.

Buck, Richard T.; Doyle, Michael P.; Drysdale, Martin J.; Ferris, Leigh; Forbes, David C.; Haigh, David; Moody, Christopher J.; Pearson, Neil D.; Zhou, Qi-Lin. Dep. Chemistry, Loughborough Univ., Loughborough, Leicestershire, UK. Tetrahedron Letters (1996), 37(42), 7631-7634. Publisher: Elsevier, CODEN: TELEAY ISSN: 0040-4039. Journal written in English. CAN 125:328854 AN 1996:644681 CAPLUS (Copyright (C) 2009 ACS on SciFinder (R)) Abstract Decompn. of Me 2-diazophenylacetate in the presence of dimethylphenylsilane and a chiral dirhodium(II) catalyst results in Si-H insertion of the intermediate carbenoid to give PhCH(SiMe2Ph)CO2Me with varying degrees of enantioselectivity (up to 47% ee; 47% using (S)-Rh2L4, LH = I).

New chiral rhodium(II) carboxylates and their use as catalysts in carbenoid transformations

New chiral dirhodium(II) carboxylates were prepd. from Rh2(OAc)4 and half phthalate esters and or pyrroles. Their use as catalysts for the decompn. of diazocarbonyl compds. studied.

Rhodium carbenoid O-H insertion reactions with phenols; a facile method for the synthesis of trialkyl 2-aryloxyphosphonoacetates and their use in the preparation of 2-aryloxy-3-phenylpropanoates

Substituted phenols undergo a facile Rh carbenoid-mediated O-H insertion reaction with (EtO)2P(O)C(:N2)CO2R (I; R = Et, Me) to give 44-86% 2-aryloxyphosphonoacetates II (R1 = e.g., H, 4-Me, 4-Cl, 2-OH, 4-PhCH2O). Phenols contg. strongly electron withdrawing groups, bulky ortho-substituents or certain ortho-heteroatom substituents show reduced or variable yields. Catechol affords a mono-adduct which cyclizes to lactate III. Aniline inserts preferentially and exclusively over phenol in a competition reaction with I (R = Et) to give (EtO)2P(O)CH(NHPh)CO2Et. II are versatile intermediates in a prepn. of 2-aryloxy-3-phenylpropenoates IV by Wadsworth-Emmons reaction with benzaldehydes R2C6H4CHO (R2 = PhCH2O, 2-Cl, H). Dissolving Mg metal redn. provides a mild method for the conversion of propenoates IV into the corresponding propanoates.

Competing O-H insertion and  -elimination in rhodium carbenoid reactions; synthesis of 2-alkoxy-3-arylpropanoates

Rhodium(II) carboxylate catalyzed decompn. of diazo esters 3 (shown as I) and PhCH2C(CO2Et)N2 4 in the presence of alcs. or water results in formation of 2-alkoxy- or 2-hydroxy-3-arylpropanoates, resp., by O-H insertion in competition with cinnamates by elimination; the ratio of insertion to elimination is dramatically affected by the carboxylate ligand on rhodium. Use of methanol-d as the alc. confirms that the alkene does not arise by elimination from the initial alkoxyester product.

Orotate complexes of rhodium(I) and iridium(I): effect of coligand, counter ion, and solvent of crystallisation on association via complementary hydrogen bonding

The new complexes [NEt3H][M(HL)(cod)] (M = Rh 1 or Ir 2; H3L = 2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, erotic acid; cod = cycloocta-1,5-diene) have been prepared by the reaction between [M2Cl2(cod)(2)] and erotic acid in dichloromethane in the presence of Ag2O and NEt3. They crystallise as dichloromethane adducts 1 . CH2Cl2 and 2 . CH2Cl2 from dichloromethane-hexane solutions. These isomorphous structures contain doubly hydrogen-bonded dimers, with additional hydrogen bonding to NEt3H+ cations and bridging CH2Cl2 molecules to form tapes. The use of (NBu4OH)-O-n instead of NEt3 gave the related complex [NBu4n][Rh(HL)(cod)] 1' which has an innocent cation not capable of forming strong hydrogen bonds and in contrast to 1 exists as discrete doubly hydrogen-bonded dimers. Complex 1' cocrystallises with 2,6-diaminopyridine (dap) via complementary triple hydrogen bonds to give [NBu4n][Rh(HL)(cod)]. dap . CH2Cl2 3. Complex 3 exhibits an extended sheet structure of associated [2 + 2] units, with layers of NBu4n, cations separating the sheets. These structural data together with those reported previously for platinum orotate complexes suggest that the steric requirements of the other ligands co-ordinated to the metal are important in influencing their hydrogen-bonding abilities. The solvent of crystallisation, the hydrogen-bonding propensity of the coligand and the nature of the counter ion also determine the type of association in the solid state.