Dienyl Carbonates Research Articles

ChemInform Abstract: Pd‐Catalyzed Allylic Alkylation of Dienyl Carbonates with Nitromethane with High C‐5 Regioselectivity.

AbstractThe investigation reveals that the structure of the ligands as well as the steric effect of the substrate are crucial factors in determining the regiochemical outcome of the reaction.

Pd-catalyzed allylic alkylation of dienyl carbonates with nitromethane with high C-5 regioselectivity

A highly regioselective palladium-catalyzed allylic alkylation of dienyl esters with nitromethane has been developed, providing selective access to the C-5 attacked products. The structures of the ligands as well as the steric effect of the substrates are important factors in determining the regiochemical outcome of the reaction.

ChemInform Abstract: Ruthenium‐Catalyzed Synthesis of Functional Conjugated Dienes from Propargylic Carbonates and Silyl Diazo Compounds.

AbstractThis reaction yields dienyl carbonates from propargylic carbonates via a 1,2‐shift of the carbonate group.

Synthesis of 1 Z,4 E,6 E‐Triene Derivatives by Chemo‐ and Regioselective Iridium‐Catalyzed Dienylation of ortho‐Aminostyrenes with Dienyl Carbonates

AbstractA chemo‐ and regioselective iridium‐catalyzed dienylation of ortho‐aminostyrene derivatives with dienyl carbonates was realized. With a catalyst generated from [Ir(cod)Cl]2 (2 mol %) and a racemic phosphoramidite ligand (4 mol %), 1Z,4E,6E‐trienes were obtained in moderate to good yields with exclusive formation of a cis double bond.

Ruthenium‐Catalysed Synthesis of Functional Conjugated Dienes from Propargylic Carbonates and Silyl Diazo Compounds

Ru being served? The reactions of propargylic carbonates with silyl diazo compounds in the presence of [Cp*RuCl(cod)] as a catalyst precursor led to the formation of dienyl carbonates in excellent yields under mild conditions (see scheme; Y = SiMe(3)).

Generation of Molecular Complexity from Cyclooctatetraene: Preparation of Optically Active Protected Aminocycloheptitols and Bicyclo[4.4.1]undecatriene

The racemic (6-cyclo-heptadienyl)Fe(CO)(3)(+) cation ((±)-7), prepared from cyclooctatetraene, was treated with a variety of carbon and heteroatom nucleophiles. Attack took place at the less hindered C(1) dienyl carbon and decomplexation of the (cycloheptadiene)Fe(CO)(3) complexes gave products rich in functionality for further synthetic manipulation. In particular, a seven-step route was developed from racemic (6-styryl-2,4-cycloheptadien-1-yl)phthalimide ((±)-9 d) to afford the optically active aminocycloheptitols (-)-20 and (+)-20.

Enantioselective, Iridium-Catalyzed Monoallylation of Ammonia

Highly enantioselective, iridium-catalyzed monoallylations of ammonia are reported. These reactions occur with electron-neutral, -rich, and -poor cinnamyl carbonates, alkyl and trityloxy-substituted allylic carbonates, and dienyl carbonates in moderate to good yields and excellent enantioselectivities. This process is enabled by the use of an iridium catalyst that does not require a Lewis acid for activation and that is stable toward a large excess of ammonia. This selective formation of primary allylic amines allows for one-pot syntheses of heterodiallylamines and allylic amides that are not otherwise accessible via iridium-catalyzed allylic amination without the use of blocking groups and protective group manipulations.

Palladium‐Catalyzed Dienylations of Chelated Enolates

AbstractIsomerization‐free reactions of dienyl carbonates with chelated amino acid ester enolates at –78 °C provide important information concerning the mechanism of these dienylations. The formation of regioisomeric products can be explained by competing SN2/SN2′ reactions, and the product distribution can be influenced by the proper choice of the reaction conditions. Chiral allylic substrates show a significant transfer of chirality. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Allylations of Chelated Enolates Using Dienyl Substrates

Isomerization-free reactions of dienyl carbonates (1-3) with chelated amino acid ester enolates at -78 degrees C provide important information concerning the mechanism of these dienylations. The formation of regioisomeric products can be explained by competing SN2/SN2' reactions, and the product distribution can be influenced by proper choice of the reaction conditions.

Sequential Catalytic Isomerization and Allylic Substitution. Conversion of Racemic Branched Allylic Carbonates to Enantioenriched Allylic Substitution Products.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Sequential Catalytic Isomerization and Allylic Substitution. Conversion of Racemic Branched Allylic Carbonates to Enantioenriched Allylic Substitution Products

A catalytic protocol for the conversion of readily accessible racemic, branched aromatic allylic esters to branched allylic amines, ethers, and alkyls has been developed. Palladium-catalyzed isomerization of branched allylic esters to terminal allylic esters, followed by sequential iridium-catalyzed allylic substitution, gave the branched allylic products in good yield with high regioisomeric and enantiomeric selectivity. Both electron-rich and electron-poor branched allylic esters gave products in >90% ee. High enantiomeric excesses were also observed for the products from the reactions of 2-thienyl acetates and dienyl carbonates.

Synthesis and reactivity of tricarbonyl(1-methoxycarbonyl-5-phenylpentadienyl)iron(1+) cation

Tricarbonyl(1-methoxycarbonyl-5-phenylpentadienyl)iron(1+) hexafluorophosphate ( 7) was prepared in two steps from tricarbonyl(methyl 6-oxo-2,4-hexadienoate)iron. While addition of carbon and heteroatom nucleophiles to 7 generally occurs at the phenyl-substituted dienyl carbon to afford (2,4-dienoate)iron products, the addition of phthalimide proceeded at C2 to afford a (pentenediyl)iron product ( 18). Complex 18 was structurally characterized by X-ray diffraction analysis.

Synthesis and reactions of cycloheptadienyl and cyclooctadienyl tungsten complexes: X-ray crystal structure of [W(CO) 2(PPh 3) 2(η 5-C 7H 9)][BF 4

Protonation of the cycloheptatriene complex [W(CO) 3(η 6-C 7H 8)] with H[BF 4] · Et 2O in CH 2Cl 2 affords the cycloheptadienyl system [W(CO) 3(η 5-C 7H 9)][BF 4] ( 1). Complex 1 reacts with NaI to yield [WI(CO) 3(η 5-C 7H 9)], which is a precursor to [W(CO) 2(NCMe) 3(η 3-C 7H 9)][BF 4], albeit in very low yield. The dicarbonyl derivatives [W(CO) 2L 2(η 5-C 7H 9)] + (L 2=2PPh 3, 4, or dppm, 5) were obtained, respectively, by H[BF 4] · Et 2O protonation of [W(CO) 2(PPh 3)(η 6-C 7H 8)] in the presence of PPh 3 and reaction of 1 with dppm. The X-ray crystal structure of 4 (as a 1/2 CH 2Cl 2 solvate) reveals that the two PPh 3 ligands are mutually trans and are located beneath the central dienyl carbon and the centre of the edge bridge. The first examples of cyclooctadienyl tungsten complexes [WBr(CO) 2(NCMe) 2(1–3-η:5,6-C 8H 11)] ( 6) and [WBr(CO) 2(NCMe) 2(1–3-η:4,5-C 8H 11)] ( 7) were synthesised by reaction of [W(CO) 3(NCR) 3] (R=Me or Pr n ) with 3-Br-1,5-cod/6-Br-1,4-cod or 5-Br-1,3-cod/3-Br-1,4-cod (cod=cyclooctadiene), respectively. Complexes 6 and 7 are precursors to the pentahapto-bonded cyclooctadienyl tungsten species [W(CO) 2(dppm)(1–3:5,6-η-C 8H 11)][BF 4] and [W(CO) 2(dppe)(1–5-η-C 8H 11)][BF 4] · CH 2Cl 2.

Syntheses and structural systematics of trialkylphosphine complexes of open titanocenes, zirconocenes and hafnocenes

The synthesis and characterization of the open hafnocene, Hf(2,4-C7H11)2(PMe3)(C7H11 = dimethylpentadienyl), is reported. Additionally, a much improved synthetic procedure has been developed for Hf(2,4-C7H11)2(PEt3). Structural data have been obtained for these complexes, and for Ti(2,4-C7H11)2(PEt3) and Zr(2,4-C7H11)2(PMe3), thereby allowing for detailed comparisons between all M(2,4-C7H11)2(PX3) species (M = Ti, Zr, Hf; X = Me, Et). The presence of the coordinated phosphines led in all cases to the adoption of the expected syn-eclipsed geometries, with the phosphines positioned by the open dienyl edges. These phosphine ligands lead to substantial alterations of the bonding patterns in these species, relative to ligand-free complexes. Most notably, the shortest M-C distances involve the central dienyl carbon atoms. Additionally, the data reveal high degrees of steric crowding within these complexes, especially for the weakly bound Ti(2,4-C7H11)2(PEt3), and also demonstrate that significant deformations which have taken place within the dienyl ligands were substantially determined by the relative sizes of the metal centers.

Reactivity of the Substituted Butadienes, Isoprene and Myrcene, with Decamethylsamarocene

The interaction of the substituted diene monomers isoprene, C5H8, and myrcene, C10H16, with a lanthanide was probed by examining their chemistry with (C5Me5)2Sm. CH2CHC(Me)CH2 reacts with (C5Me5)2Sm to form the bimetallic [(C5Me5)2Sm]2[μ-η2:η4-CH2CHC(Me)CH2], 1. Both (C5Me5)2Sm components in 1 exhibit trivalent metrical parameters. One Sm is oriented toward all four of the dienyl carbon atoms at distances of 2.604(9)−2.799(8) A, and the other Sm interacts with only two carbons at distances of 2.544(9) and 2.674(9) A. CH2CHC(CH2)CH2CH2CHCMe2 reacts with (C5Me5)2Sm to form [(C5Me5)2Sm]2[μ-η2:η4-CH2CHC(CH2)CH2CH2CHCMe2], 2, which is similar in structure to 1. The double bond of the pendant olefinic substituent attached to the diene in myrcene does not coordinate. The structures of 1 and 2 are compared to the (C5Me5)2Sm/PhC⋮CPh bimetallic reaction product [(C5Me5)2Sm]2[μ-η1:η1-PhCCPh], 3, which also contains two (C5Me5)2Sm units attached to an unsaturated hydrocarbon, but has equivalent trivalent (C5Me5)2Sm u...

The synthesis and reactions of A-ring aromatic steroid complexes of manganese tricarbonyl

Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO) 5 +BF 4 − in CH 2Cl 2 yields the corresponding [(steroid)Mn(CO) 3]BF 4 salts 1 and 2 as mixtures of α and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO) 3]BF 4 · CH 2Cl 2 ( 1) having the Mn(CO) 3 moiety on the α side of the steroid is reported: space group P2 1 with a=10.3958(9), b=10.9020(6), c=12.6848(9) Å, β=111.857(6)°, Z=2, V=1334.3(2) Å 3, ϱ calc=.481 cm −3, R=0.0508, and wR=0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear MnCO linkages. The nucleophiles NaBH 4 and LiCH 2C(O)CMe 3 add to [(β-estradiol 3,17-dimethyl ether)Mn(CO) 3]BF 4 ( 2) in high yield to give the corresponding α- and β-cyclohexadienyl manganese tricarbonyl complexes ( 3). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The α and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo-CH 2C(O)CMe 3 substituent is reported (complex 4): space group P2 12 12 1 with a=7.5154(8), b=15.160(2), c=25.230(3) Å, Z=4, V=2874.4(5) Å 3, ϱ calc=1.244 g cm −3, R=0.0529 and wR2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 Å out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths.

Oxidation of lipids. XI. Spin trapping and identification of peroxy and alkoxy radicals of methyl linoleate

Spin trapping of peroxy and alkoxy radicals generated from the hydroperoxide of methyl linoleate was studied using methyl- N-duryl nitrone (MDN) and phenyl- N-tert-butyl nitrone (PBN) as spin traps. The conjugated dienyl carbon radical was also generated from methyl linoleate and spin-trapped. The spin adducts of peroxy, alkoxy, and dienyl carbon radicals were observed by ESR and their hyperfine splitting constants were determined. The spin adducts of peroxy and alkoxy radicals could be distinguished clearly with MDN.

Correlation of the reactivity of coordinated π-hydrocarbons with electronic parameters : I. Indo calculations on the cation [(C 6H 7)Fe(CO) 3] +

INDO calculations on the cation [(C 6H 7)Fe(CO) 3] + suggest that there is a correlation between the bond index (or free valence) values at each dienyl carbon and the site of nucleophilic addition.