Related Dienes Research Articles

N-Methylation of Amines with Methanol Catalyzed by Iridium(I) Complexes Bearing an N,O-Functionalized NHC Ligand

A set of neutral [IrBr(L2)(κC-tBuImCH2PyCH2OMe)] and cationic [Ir(L2)(κ2C,N-tBuImCH2PyCH2OMe)]PF6 (L2 = cod, (CO)2) Ir(I) compounds featuring a flexible lutidine-derived polydentate ligand having NHC and −OMe as donor functions have been evaluated as catalyst precursors for the N-methylation of aniline using methanol both as a reducing agent and a C1 source. The carbonyl complexes are somewhat more active than the related diene compounds with the neutral compound [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] being the more active. A range of aromatic primary amines, including heterocyclic amines, have been selectively transformed into the corresponding N-methylamino derivatives using this catalyst at a low catalyst loading (0.1 mol %) and substoichiometric amounts of Cs2CO3 (half equiv) as a base, in methanol at 423 K. For aliphatic primary amines, selective N,N-dimethylation was achieved under the same catalytic conditions. The unselective deprotonation of the methylene linkers in [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] affords two isomeric neutral complexes featuring a coordinated dearomatized pyridine core, which were converted into [Ir(OMe)(CO)2(κC-tBuImCH2PyCH2OMe)] upon addition of methanol. This compound undergoes thermal activation of a C–H bond of the tert-butyl group to give the cyclometalated iridium(I) complex [Ir(CO)2{κ2C,C-(-CH2Me2C-ImCH2PyCH2OMe)}] featuring a bidentate C,C-coordinated NHC ligand. Mechanistic investigations support a borrowing hydrogen mechanism proceeding through iridium(I) intermediates with the methoxo complex as the catalytic active species and the cyclometalated complex as the catalyst resting state. Deuterium labeling experiments have demonstrated that both species are in equilibrium under catalytic conditions, which is consistent with the exhibited catalytic activity of the cyclometalated complex.

Syntheses and Structures of Functionalized [9]Cycloparaphenylenes as Carbon Nanohoops Bearing Carbomethoxy and N-Phenylphthalimido Groups.

Functionalized [9]cycloparaphenylenes ([9]CPPs) bearing nine aromatic units in the macrocyclic structures were synthesized. The macrocyclic structures were substituted with carbomethoxy or N-phenylphthalimido groups. The Diels-Alder reaction of (E,E)-1,4-bis(4-bromophenyl)-1,3-butadiene or a related diene with dimethyl acetylenedicarboxylate followed by the nickel-mediated homocoupling reactions and oxidative aromatization produced the functionalized [9]CPPs. Treatment of a resultant [9]CPP with aniline or 1,4-diaminobenzene gave the corresponding N-phenylphthalimides. The X-ray structure of a [9]CPP bearing six carbomethoxy groups was obtained.

Identification and characterisation of a novel mono-unsaturated highly branched isoprenoid (HBI) alkene in ancient Arctic sediments

The occurrence of a novel C25 highly branched isoprenoid (HBI) mono-unsaturated hydrocarbon in Arctic marine sediments from the Fram Strait is described. The structure was determined following synthesis from a closely related diene and NMR spectroscopic analysis. The position of the double bond was confirmed by oxidation (RuO4) and comparison of the mass spectrum of the resulting C19 ketone with that of an authentic sample synthesised previously. The same C19 ketone was also present following oxidation of the Fram Strait sediment extracts. The source of the novel HBI monoene biomarker is not known, but is believed to be certain marine diatoms on the basis of structural similarities with other HBIs from such sources. It does not, however, appear to be biosynthesised by Arctic sea ice diatoms, unlike its regio isomer, IP25, an established proxy for Arctic sea ice. Alternatively, it may represent a diagenetic product of the sea ice diatom biomarker IP25; this seems unlikely, however, on the basis of their respective structures. Since the new HBI monoene and IP25 possess similar gas chromatographic and mass spectral properties, but probably have contrasting sources, we suggest that future paleo sea ice reconstruction studies based on the occurrence of IP25 should pay further attention to the rigorous assignment of this biomarker in marine sediment extracts. Some suggestions for achieving this, based on analytical purification and mass spectrometric measurements, are provided.

Sulfinyl-Mediated Stereoselective Overman Rearrangements and Diels–Alder Cycloadditions

The Overman rearrangement of allylic sulfinyl trichloroacetimidates affords sulfinyl trichloroacetamides with high stereoselectivity and excellent yields. Bis-allylic substrates lead to amido 2-sulfinyl butadiene derivatives in excellent yields, with total chemo- and diastereoselectivity. The Diels-Alder cycloaddition of related dienes is controlled by the sulfoxide moiety.

ChemInform Abstract: Simple Synthesis and the Diels-Alder Reaction of 3-(p-Tolylthio)-2-( trimethylsilyloxy)-1,3-butadiene.

The reaction of 3-(p-tolylsulfinyl)-2-butanone with trimethylsilyl trifluoromethanesulfonate in the presence of diisopropylethylamine gave 3-(p-tolylthio)-2-(trimethylsilyloxy)-1,3-butadiene (2) quantitatively. The Diels–Alder reactions of 2 and the related dienes with methyl acrylate were studied.

Efficient trans-Selectivity in the Cyclocondensation of (S)-2-[2-(p-Tolylsulfinyl)phenyl]acetaldehyde with Activated Dienes Catalyzed by Yb(OTf)3

Reactions of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde 1 with Danishefsky's and related dienes took place in the presence of Yb(OTf)3 in a completely stereoselective manner, mediated by a remote sulfinyl group (1,5-asymmetric induction), to afford the corresponding 2,3-dihydro-4H-pyran-4-ones. These reactions followed a stepwise mechanism, as was corroborated by isolation of the corresponding intermediates, with a high level of trans-selectivity for 4-methyl-substituted dienes. Treatment of the adducts with Raney Ni provided concomitant cleavage of the C-S bond and reduction of the conjugated carbonyl grouping.

Stereodivergent Approach to the Asymmetric Synthesis of Bacillariolides: A Formal Synthesis of ent-Bacillariolide II

[reaction: see text] Asymmetric synthesis of densely functionalized bicyclic frameworks for entry into bacillariolides I/III and ent-bacillariolide II is reported. The key features are ring-closing metathesis of a pair of diastereomerically related dienes obtained through a stereodivergent route from a R-(+)-glyceraldehyde derivative, transformation of a nonstereoselective cyclopentene ester enolate alkylation process to a completely stereoselective one through alkylation of a bulky ester enolate with a bulky electrophile, and a remote silyloxymethyl group directed epoxidation.

Chiral Copper Complexes of Phosphino Sulfenyl Ferrocenes as Efficient Catalysts for Enantioselective Formal Aza Diels—Alder Reactions of N‐Sulfonyl Imines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Chiral copper complexes of phosphino sulfenyl ferrocenes as efficient catalysts for enantioselective formal Aza Diels-Alder reactions of N-sulfonyl imines.

In the presence of a catalytic amount of silver perchlorate, copper(I) bromide complexes of planar chiral 1-phosphino-2-sulfenylferrocenes behave as very efficient chiral Lewis acids catalysts in the formal Aza Diels-Alder reaction of N-arylsulfonyl aldimines with electron-rich dienes (Danishefsky's and related dienes). Mixing of equimolar amounts of the readily available enantiopure ferrocenyl P,S-bidentate ligand and CuBr quantitatively affords the precatalyst Cu complex as an air-stable solid. This catalytic asymmetric procedure has a broad structural scope: aldimines of aromatic, alpha,beta-unsaturated, and even enolizable aliphatic aldehydes have been successfully used. The corresponding 2,3-dihydro-4-pyridones were obtained in good yields (57-90%) and with homogeneously high enantioselectivity (82-97% ee).

Preparation of N-Heterocycles by Radical Cyclisation of Enamides Mediated by Manganese(III) or Copper(I). A Comparison of Cyclisation Methods

Reaction of enamides with manganese(III) acetate or copper(I) chloride/bipyridine has been investigated. In both cases, an initial 5- endo- trig radical cyclisation reaction took place to produce functionalised pyrrolidinones. The copper(I)-mediated cyclisations were very efficient and bicyclic dienes could be isolated in >80% yield, while the corresponding manganese(III) reactions were generally more problematic, giving related dienes in lower yield (35–52%).

Towards a tandem-radical macrocyclization-transannular cyclization approach to steroids: Transannular cyclizations of a macrocyclic core

The triple transannular radical cyclization of 1-cyano-5-methyl-1-phenylseleno-8-hydroxy-4,9,13-cycloheptadecatriene ( 1a) provided a product 2 possessing the steroid ring skeleton of unassigned configuration in 4% isolated yield. A high yielding transannular cyclization of the related diene lacking the Δ 4,5double bond identifies the second cyclization as the Achilles heel of the triene cyclization.

Synthesis of functionalized hexahydro-, octahydro-, and decahydro-1H-phenalenes via Diels–Alder reactions of 1-methylene-4a-methoxycarbonyl-1,2,3,4,4a,5,6,7-octahydronaphthalene and related dienes

The results of a study of Diels–Alder reactions of the bicyclic dienes 6–8 with a variety of dienophiles are reported. Although 6 and 7 undergo cycloaddition reactions smoothly and efficiently, thermal Diels–Alder reactions of 8 are generally sluggish or, under the conditions investigated, do not proceed at all. Additions of tetracyanoethylene (TCNE) to 6–8 are highly face-selective, with preferential attack of the dienophile on the side of the dienes opposite to the angular methoxycarbonyl group. Reaction of 7 with maleic anhydride (MAN) is completely face-selective and proceeds preferentially via an endo transition state. Diels–Alder reactions of 6 and 7 with methyl acrylate (MAC) and nitroethylene (NE) are entirely regioselective, but the face-selectivities, which vary from ~2:1 to ~3:1, are rather low. The use of this chemistry as a method for the synthesis of functionalized, stereochemically defined, perhydro-1H-phenalenes is demonstrated.

Simple Synthesis and the Diels–Alder Reaction of 3-(p-Tolylthio)-2-(trimethylsilyloxy)-1,3-butadiene

Abstract The reaction of 3-(p-tolylsulfinyl)-2-butanone with trimethylsilyl trifluoromethanesulfonate in the presence of diisopropylethylamine gave 3-(p-tolylthio)-2-(trimethylsilyloxy)-1,3-butadiene (2) quantitatively. The Diels–Alder reactions of 2 and the related dienes with methyl acrylate were studied.

A correlation between the rates of photoinduced long-range intramolecular electron transfer in rigidly linked donor-acceptor systems and computed π,π and π *,π * splitting energies in structurally related dienes

It has been found that the rates of photoinduced intramolecular electron transfer in a series of rigidly linked donor (dimethoxynaphthalene)-acceptor (dicyanovinyl) systems, in which the length and configuration of the hydrocarbon bridge are varied, correlate well with the computed Koopmans' theorem STO-3G π *,π * splitting energies in a structurally related series of dienes. It is proposed that the origin of this correlation lies in a through-bond coupling mechanism which obtains between the π * LUMOs of the chromophores and the bridge σ and σ * orbitals in both series of molecules.

Synthesis of 4-(4'-Chlorophenyl)-5-Phenyl-1,2-Dihydronaphthalene

BF3-catalysed cyclization reactions of 1-(biphenyl-2'-y1)- 1-(4″-chlorophenyl)but-3-en-1-ol yielded none of the desired title compound but only 9-(4'-chloropheny1)-10-ethylphenanthrene and 9-allyl-9-(4'-chlorophenyl) fluorene by alternative cyclization pathways. Corresponding cyclization of the related diene 1-(biphenyl-2'-yl)-1-(4″-chlorophenyl)buta-1,3-diene also failed to yield the desired title compound but gave instead the unexpected product 9-(4'-chlorophenyl) phenanthrene through a novel mechanism. Flash pyrolysis of l-(biphenyl-2'-yl)-l-(4″-chlorophenyl)buta-1,3-diene gave the desired compound as a minor constituent of the reaction mixture, the major constituent being 4-(biphenyl-2'-yl)-7-chloro- 1,2-dihydronaphthalene.

A study of the diels-alder reaction of 3-oxabicyclo[3.3.0]oct-1(5)-ene-2,4-dione with cyclopentadiene and some related dienes

The reaction of 3-oxabicyclo[3.3.0]oct-l(5)ene-2,4-dione, 2, with cyclopentadiene, 3, 5,5-diethoxycyclopentadiene, 4, and 6,6-dimethylfulvene, 5, is studied. Reaction of 2 and 3 yields the expected endo-adduct, while reaction of 2 and 5 gives a mixture of the endo- and exo-adducts whose ratio is slightly dependent on the reaction conditions. Attractive electrostatic interactions in the transition state leading to the exo-adduct can explain the absence of endo stereoselectivity in the last reaction. Steric factors seem to be responsible for the absence of reaction between 2 and 4. The analysis of the 13C NMR spectra of these adducts and some derived compounds confirms the tentative configuration assignment carried out on the basis of PMR data. Also, the synthesis of dimethyl(1R,2S,6R,7S)-10-oxotricy-clo [5.2.1.0 2.6]decane2,6-decarboxylate, 1, from the endo-adduct of the reaction of 2 and 5, is described

The Effects of Homoconjugated Cyclopropane and Oxirane Rings on the Diels‐Alder Reactivity of 2,3‐bis (methylidene)norbornane

AbstractPreparation of 6exo, 7exo‐bis (methylidene)‐tricyclo[3.2.1.02,4]octane (6) is described. The reactivity of 6 towards tetracyanoethylene is evaluated and compared with that of exo‐2,3‐epoxy‐5,6‐bis (methylidene)norbornane (5), 2,3‐bis‐(methylidene)norbornane (1) and other related dienes. The cyclopropane group in 6 exerts an unsignificant rate retardation effect on the Diels‐Alder reactivity of this diene relative to that of 1, whereas a relatively important rate retardation effect is caused by the exo‐oxirane ring in 5. The observed effects are probably due to electronic factors (through‐space and through‐bond interactions).

Preparation and thermolysis of exo-and endo-Tricyclo[6,2,1,02,7] undeca-3,5,9-triene

Syntheses of exo- and endo-tricyclo[6,2,1,02,7]undeca-3,5,9-triene, (3) and (4) respectively, are described. Both trienes undergo ready π4s+ π28 cycloreversion to yield cyclopentadiene and benzene at 40-60�C, the exo-triene (3) being slightly more reactive. At 60�C, for (3) k = 2.29x 10-3 s-1, ΔH? = 104.1 � 4.2kJ mol-1, ΔS? =14.6 � 1.6 mol-1 K-1, while for (4) k = 5.25 x 10-3s-1, ΔH? =ll5.0 � 3.3 kJ mol-1, ΔS? = 34.3 � 13.0 J mol-1 K-1 .� The cycloreversion of (3) and (4) are believed to be concerted reactions. The related dienes exo- and endo-tricyclo[6,2,1,02,7]undeca-3,5-diene, (25) and (28) respectively, have also been prepared, and are stable up to 200�C. At 300�C, interconversion between (25) and (28) occurs, apparently via bicyclo[6,2,1]undeca-2,4,6-triene. The relationship of the trienes (3) and (4) to the recently described bicyclo[6,2,l]undeca-2,4,6,9-tetraene is discussed.

Studies on cyclitols—XVII : Structural requirements for abnormal hydroxylation of dienes by permanganate

Abnormal hydroxylation by permanganate of cyclopentadiene ( 1a) and 1,3-cyclohexadiene ( 1b) has been described previously. This pathway, referred to as the epoxidic pathway, gives (1,2,3,4/0)-1,2-epoxydiols ( 3), and (1,2,3/4)- and (1,2,4/3)-tetrols ( 5 and 6) in addition to normal products. A second abnormal pathway, described by other authors, converts 1,5-hexadiene ( 7) and related dienes ( 9) into tetrahydrofurandiols ( 8 and 10). This is referred to as the oxacyclane pathway. The study has now been extended to include 1,4-cyclohexadiene ( 11) and 1,5-cyclooctadiene ( 17). VPC analysis using authentic markers shows that 11 gives only normal products, neither epoxydiol nor ( cis/trans)-tetrol being detectable. The study of 17 is less complete; only normal products have been identified, but in the absence of authentic abnormal products for comparison, the conclusions are only tentative. 17 is a constrained analogue of 7, and might possibly be expected to react by the oxacyclane pathway. Examination of models suggests that 17 probably cannot assume a conformation leading to the transition state necessary to give analogues of 8 by the oxacyclane pathway, and also that in any conformation that would lead to the necessary transition state, the methylenic hydrogens would seriously hinder the approach of the reagent. Measurements of the models also show that the interatomic distances, among the carbon atoms in the double bonds, are markedly different in 11 with respect to 1a and 1b. On the other hand, the distances in 7 are more like those in 1. It is proposed that the epoxidic pathway requires conjugated double bonds in the substrate, and that the oxacyclane pathway requires proximity of isolated double bonds. 11 does not react by the oxacyclane route because the proposed bicyclic product 21 would be too strained to be formed.

X-ray evidence for contrasting stereochemistry in related diene addition products

2,3-Dichloro-5,6-dicyanobenzoquinone(DDQ) reacts readily with 1,5,5-trimethyl-3-methylenecyclohexene to give an adduct having endo-stereochemistry which crystallises in the monoclinic space group P21/n with lattice parameters a= 9·06 ± 0·01, b= 16·10 ± 0·01, c= 12·00 ± 0·01 A, β= 96° 42′± 5′, Z= 4. In contrast the addition of cyclopentadiene to DDQ under similar conditions yields an exo-stereomer as the principle product which is monoclinic, space group p21/n with unit-cell dimensions a= 8·051 ± 0·005, b= 11·14 ± 0·01, c= 13·55 ± 0·01 A, β= 94° 28′± 6′, Z= 4. Both structures were solved by centrosymmetric symbolic addition and refined by least-squares calculations to R= 0·112 for 955 reflections and R= 0·082 for 1225 reflections respectively.