Allylic Systems Research Articles

Synthetic Anthracyclines From Anthraquinones

Our syntheses of important and novel daunomycinones, aklavinones, fridarnycins and vineomycinones, from 1,4- or 1,5-dihydroxyanthraquinones, are reviewed. The reductive Claisen rearrangement has proven to be the most versatile of the methods developed for appending rings or functionalized side chains. Some novel polycyclic systems have been made, some interesting new properties of substituted quinizarins and anthrarufins uncovered, and new methods for elaboration of allyl systems developed.

Stereoselective Synthesis of Acyclic Terpenes

Allylation reaction is one of the most important process in organic synthesis due to the synthetic flexibility of allylic systems. Described herein are the new methods to control regio-and stereochemistry of allylic compounds for efficient synthesis of acyclic terpenes. (1) Remarkable SN2'-, (E) -, and antiselectivities are observed in the coupling reaction between Grignard reagents and allylic phosphates in the presence of a copper (I) salt. (2) Stereochemically homogeneous mono-and di-substituted allylmetals can be directly prepared from the corresponding allylic halides and reactive metals at low temperature. (3) Allylic barium reagent reacts with a variety of carbonyl compounds to produce the homoallylic alcohol with remarkably high α -selectivity with retention of stereochemistry of the starting halides.

3,3]Sigmatropic ring expansion of cyclic thionocarbonates. 8. highly stereoselective synthesis of ( Z- or ( E)-double bonds by controlling chairlike-boatlike transition states in the [3,3]sigmatropic rearrangement of 8-membered thionocarbonates

A highly stereoselective synthesis of ( Z)- or ( E)-double bonds in 10-membered thiolcarbonates ( 3) was successfully conducted by controlling the chairlike-boatlike transition states in the [3,3]sigmatropic rearrangement of 8-membered thionocarbonates ( 2). The geometry of the product appeared to be highly dependent on the substituent pattern in the allylic system of the substrates ( 1). The 10-membered thiolcarbonates ( 3) were readily converted to ( Z)- or ( E)-allylic thiolcarbonates ( 11). Treatment of ( Z)- 3j or 3i with lithium in liquid ammonia afforded ( Z)-trisubstituted or tetrasubstituted olefins ( 12j and 12i) in high yields.

The diastereoselectivity of electrophilic attack on trigonal carbon adjacent to a stereogenic centre

This paper summarises the work described in the nine papers immediately preceding it. The diastereoselectivity of attack on a trigonal carbon adjacent to a stereogenic centre is governed by the general rule expressed most simply by the drawing 34, except when the medium-sized group on the stereogenic centre is methyl at the same time as the substituent cis to the stereogenic centre is a hydrogen atom, when reaction may or may not take place in the sense of the drawing 35. When the large group on the stereogenic centre is a silyl group, the diastereoselectivity of electrophilic attack is high, as shown by enolate alkylations and aldol reactions, and the reactions of allylsilanes with osmium tetroxide, peracid, the Simmons–Smith reagent and boranes. The protodesilylation of allylsilanes can be used to control the geometry of trisubstituted double bonds, notably those exocyclic to a ring, provided that the medium-sized group on the stereogenic centre is an isopropyl group. Two regiocontrolled syntheses of allylsilanes that are secondary at both ends of the allylic system are reported in the last two papers. The first of the two syntheses gives largely trans-allylsilanes, but the second provides good control, of double bond geometry with either the cis- or the trans-configuration. Both syntheses are amenable to the synthesis of homochiral allylsilanes.

ChemInform Abstract: γ‐Selective Cross‐Coupling Reaction of Allyltrifluorosilanes: A New Approach to Regiochemical Control in Allylic Systems.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

.gamma.-Selective cross-coupling reaction of allyltrifluorosilanes: a new approach to regiochemical control in allylic systems

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT.gamma.-Selective cross-coupling reaction of allyltrifluorosilanes: a new approach to regiochemical control in allylic systemsYasuo Hatanaka, Yasuo Ebina, and Tamejiro HiyamaCite this: J. Am. Chem. Soc. 1991, 113, 18, 7075–7076Publication Date (Print):August 1, 1991Publication History Published online1 May 2002Published inissue 1 August 1991https://doi.org/10.1021/ja00018a076RIGHTS & PERMISSIONSArticle Views878Altmetric-Citations70LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (288 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Thiophendioxid-Komplexe des Cobalts

Thiophene-1,1-dioxide (TDO) is thermally unstable and can be stabilized by coordination to metals in low oxidation states as hitherto shown in the case of some iron carbonyl compounds. We now present examples of cobalt complexes such as CoCp(η 4-TDO) ( 4) and their derivatives: CoCp(η 4-2,5-diphenylthiophenedioxide) ( 5), CoCp(η 4-3,4-diphenylthiophenedioxide) ( 6), CoCp(η 4-tetraphenylthiophenedioxide) (7). CoCp(η 4-2,5-di-t-butylthiophenedioxide) ( 8) and CoCp(η 4-di-t-butylthiophenedioxide) ( 9). Also complexes with the η 3-ligand 2-hydrothiophenedioxide (TDO-H), containing a cyclic allyl system have been obtained: Co(CO) 3(TDO-H) ( 11). One or two CO groups may be substituted by a variety of organophosphanes and phosphites including the chelating diphosphanes DPPM and DPPE. All compounds have been characterized by 1H and 13C NMR methods. In addition the crystal structures of 4, 7 and Co(CO)(η 2-DPPE)(TDO-H) ( 11i) have been determined.

Conjugate Addition of Allylic Groups to α,β-Enones via Photoinduced Electron Transfer Reaction of Allylic Stannanes

Abstract Conjugate addition of allylic groups, including allyl and cinnamyl systems, to a variety of α,β-unsaturated ketones could be achieved by photoirradiation with allylic stannanes.

MNDO calculations on borazine derivatives. The substitution of one [HNBH] fragment for one [HCCH] fragment in benzene to form the azaborines and the nature of the cyclotrimer of the 1,2-isomer

The three azaborine isomers with the formula C4H6BN, 1,2-, 1,4-, and 1,3-azaborine (I, II, and III), have been examined using MNDO (modified neglect of diatomic overlap) calculations. The most stable azaborine was I (heat of formation -8.147 kcal/mol), followed by II (+11.60 kcal/mol) and III (+16.64 kcal/mol). Qualitatively, although the π- and π*-orbitals calculated for the azaborines exhibited an ordering similar to that in benzene and borazine, the HOMO/LUMO energy differences (9.27, 9.68, and 8.44 eV, respectively) were smaller than was the difference calculated for borazine (12.81 eV), but of the same magnitude as the difference for benzene (9.76 eV). With the exception of borazine, each molecule had a π-orbital for the HOMO and a π*-orbital for the LUMO; borazine's LUMO was a π*-orbital. The calculated shapes and atomic contributions for the π-and π*-orbitals of the azaborines were best described as “hybrids” of the π- and π*-orbitals of benzene and borazine. As was observed for the π- and π*-orbitals of borazine, the azaborines exhibited increased orbital density at the nitrogen atom in the π-bonding orbitals and at boron in the π-antibonding orbitals, as would be predicted from electronegativity considerations. Although I and II exhibited significant double- and single-bond localization, all of the ring bonds in III were delocalized. The delocalization in III was not uniform but, rather, resembled two inequivalent fused allyl systems. The cyclotrimer (IV) of 1,2-azaborine (heat of formation -44.07 kcal/mol), based purely on thermodynamic considerations, was predicted to form spontaneously from three monomer molecules with the concurrent loss of three molecules of dihydrogen. The cyclotrimers that could theoretically be produced from 1,2-azaborine without the loss of dihydrogen (IVc and IVt) were each calculated to be less stable (heats of formation +24.45, and +33.29 kcal/mol, respectively) than was the experimentally observed IV. The carbon molecules triphenylene (TP) and cis- and trans-4a,4b,8a,8b,12a,12b- hexahydrotriphenylene (TPc and TPt) (heats of formation +76.79, +101.6, and +103.1 kcal/mol, respectively) were each calculated to be less stable than were the azaborine cyclotrimer analogs, as was observed in comparisons of benzene with the azaborines and borazine.

{Bis[bis(trimethylsilyl)methyl]stannio(II)}bis(η2-ethen)nickel(O) und verwandte Verbindungen, Teil I

{Bis[bis(trimethylsilyl)methyl]stannio(II)}bis(η2-ethene)nickel(0) and Related Compounds, Part II The coordinatively unsaturated (16e) (ethene)nickel(0) stannylene complex (C2H4)2Ni=Sn{CH(SiMe3)2}2 (1) reacts with 1,6-heptadiene with preservation of the Ni=Sn bond to yield quantitatively the 1,6-diene derivative (η2,η2-C7H12)Ni=Sn-{CH(SiMe3)2}2 (2). The alkene ligands of both 1 and 2 are readily displaceable. Compounds 1 and 2 react with butadiene at −50°C by a 4-e oxidation of the metal-metal pair Ni(0)/Sn(II) to Ni(II)/Sn(IV) and concomitant reduction of two butadiene molecules to butenediyl moieties to afford stereo-selectively the 16-e complex Ni-cis-{η3(Ni),η1(Sn)-anti-C3H4CH2}2Sn{CH(SiMe3)2}2 (3). Similarly, the reaction of 1 or 2 with isoprene yields regio- and stereoselectively the derivative Ni-cis-{η3(Ni,η1(Sn)-anti-C3(3-Me)H3CH2}2Sn{CH-(SiMe3)2}2 (4). These reactions imply the cleavage of one formal NiSn bond and the formation of two new SnC bonds. Upon reaction of 3 with PMe3 the configuration of the allyl system changes and, again fully stereoselectively, the 18-e addition compound (Me3P)Ni-cis-{η3(Ni),η1(Sn)-syn-C3H4-CH2}2Sn{CH(SiMe3)2}2 (5) is formed. When 5 is treated with BPh3, the phosphane ligand is trapped and, kinetically controlled, Ni-cis-{η3(Ni),η1(Sn)-syn-C3H4CH2}2Sn{CH(SiMe3)2}2 (6) is obtained as a stereoisomer of 3. At 40°C 6 slowly rearranges into the thermodynamically stable stereoisomer Ni-trans-{η3(Ni),η1(Sn)-syn-C3H4CH2}2Sn{CH(SiMe3)2}2 (7). Mild protolysis of 3 with pyridine hydrochloride or hydrobromide affords region and stereoselectively (Me3Si)2CH}2(X)SnNi-(η3-1-MeC3H4)(NC5H5) (X = C1, 8a; Br, 8b). In the course of this protonation reaction one butadiene molecule is eliminated, accompanied by a 2-e reduction of the metal-metal pair Ni(II)/Sn(IV) to Ni(II)/Sn(II) and, at the expense of two SnC bonds, reformation of a NiSn bond. All compounds are isolated in high yield and fully characterized by 1H-, 13C-, and 31P-NMR spectroscopy.

Diazadiene stabilized palladacyclopent 2 enes and the catalytic addition of various allylic systems to dimethyl acetylenedicarboxylate

With diazadiene (dad=Rn=Cr'-Cr=NR)as co-ligand the palladacyclopent-2-enes 3 formed by direct coupling of a 1-alkene and an acetylenedicarboxylic acid esters can be trapped. With activated 1-alkanes such as allylic alcohols the reaction becomes catalytic, yeilding linear addition-products4-11 from two molecules of the alkene and one molecule of the alkyne; no simple reductive elimination occurs, but instead elimination of one mole of water takes place. Allylic esters react analogously but a cyclic 1:2-addition-product 15 (also formed by loss of the leaving group) is the main product. The elimination of the leaving group is probably the driving force of the reaction, since only β-H-transfer that make elimination possible are observed.

Alkylation of allylic derivatives. 17. Cross-coupling reactions of diallylic pivalates with butyl- and phenylcopper reagents

Cross coupling (Z)-1-phenhyl-1,4-pentadien-3-yl pivalate (cis-1-OPiv) with LiCu(CN)Bu, LiCuPh 2 , and LiCu(CN)Ph gives only the fully conjugated γ-coupling product. The relationship between structure and reactivity was also investigated. Generally, coupling occurs at the least-substituted allylic system; mechanistic implications are discussed

Short and Supershort Cr–Cr Distances: A Vanishing Borderline Between Metal–Metal Bonds, Magnetic Couplings and Ligand Artifacts

Abstract The structural features of three classes of Cr(II) compounds (alkoxides, amides, aryls) are critically reviewed with the aim of investigating the role of ligand bridging interactions in the formation of short Cr–Cr quadruple bonds. A systematic failure of Cr–Cr bond formation is observed with either monodentate or bidentate ligands. Fairly short Cr–Cr contacts are easily elongated and dinuclear structures cleaved by simply coordinating a molecule of solvent either to chromium or to the alkali cation present in anionic chromates. Conversely, extremely short Cr–Cr contacts are almost invariably formed when particular bridging ligands with a three-center chelating geometry and the electronic configuration of an allylic system have been used. Comparison of the magnetic properties of two series of Cr(II) aryls and pyrrolyls, where the three center chelating geometries of the ligands have been progressively modified, indicated that three-center chelating ligands are able to determine the dimeric aggreg...

ChemInform Abstract: Trifluoromethylated Allylic Anion and Radical. Generation by the Electronic Inversion of π‐Allylic Palladium Complex by Samarium Diiodide.

AbstractTreatment of the acetate (I), derived from an allylic alcohol bearing a trifluoromethyl group at the end of the allylic system, with samarium(II) iodide in the presence of Pd(PPh3)4 generates trifluoromethylated π‐allylic palladium complexes which are further converted to the difluoro diene (II) and the two dimers (III) and (IV).

ChemInform Abstract: The Nitrogenated Allylic System as an Intramolecular Nucleophile: A New Route to Pyrazoles.

AbstractNitrosation of the N‐allylcarboxamides (I) yields the N‐nitroso derivatives (III) which undergo cyclization upon treatment with calcium carbonate in dioxane, forming the pyrazoles (IV), together with the allyl carboxylates (V).

ChemInform Abstract: Application of Elementoorganic Compounds of 15th and 16th Groups in Organic Synthesis. Part 82. An Efficient SbCl3‐Metal System for Allylation, Reduction and Acetalization of Aldehydes.

AbstractA novel and highly efficient method of allylation, reduction and acetalization of aldehydes is described, which works under very mild conditions.

Synthesis of the novel sarcosine and proline (FK-525) analogs of FK-506: rearrangement of the allylic ester system

Synthesis of the novel sarcosine and proline (FK-525) analogs of FK-506: rearrangement of the allylic ester system

ChemInform Abstract: Diphosphinonitrenium and ‐phosphenium Cations, Jahn‐Teller Distorted Allyl Systems

Ab initio calculations at SCF, MCSCF, and ACPF level were performed on a series of the phosphenium- and nitreniumcation family. These show that they possess an allylic π-system with 4 electrons, which is distorted from planarity when the terminal groups of the allylic system are PR2 (R H) fragments. The distortion is such as to adopt C2 symmetry, and is the consequence of Jahn-Teller distortion via mixing of the energy highest π2 orbital with an energetically low lying δ* orbital. The latter interaction is only operative if a symmetry breaking from C2v to C2 symmetry occurs. The importance of Jahn-Teller distortion on the biradical character in these systems is investigated by correlation calculations.

Reactions of coordinated ligands. Part 47. Synthesis, structure, and reactivity of [.eta.4(5e)-butadienyl]ruthenium complexes: crystal structures of CpRu:C(Ph)-.eta.3-[C(Ph)C(Ph)CH(Ph)], CpRuC(Ph):C(Ph)-.eta.2-[C(Ph):CH(Ph)]P(OMe)3, and CpRu2[.mu.-(Z)-C(Ph):CH(Ph)](CO)2(.eta.4-C4Ph4)

The chemistry of the first example of a {eta}{sup 4}(5e)-butadienyl complex is described. Reaction of (CpRu(NCMe)({eta}{sup 4}-C{sub 4}Ph{sub 4}))(BF{sub 4}) with K(BHBu{sub 3}{sup a}) affords CpRu{double bond}C(Ph)-{eta}{sup 3}-(C(Ph)C(Ph)CH(Ph)) (5), which was structurally identified by single-crystal X-ray crystallography. Compound 5 is triclinic, space group P{anti 1} (No. 2); a = 10.156 (5), b = 10.996 (5), c = 13.145 (6) {angstrom}, {alpha} = 112.12 (4), {beta} = 101.20 (4), {gamma} = 103.76 (4){degree}. The molecule contains an open-chain {eta}{sup 4}(5e)-butadienyl system, in which the CpRu fragment is double bonded to C(1) (Ru-C(1) = 1.896 (5) {angstrom}), the remaining three carbon ruthenium distances Ru-C(2) (2.204 (5) {angstrom}), Ru-C(3) (2.152 (4) {angstrom}), and Ru-C(4) (2.154 (6) {angstrom}) being appropriate for an {eta}{sup 3}-allyl system. A mechanism is proposed for the formation of 5 involving conrotatory ring-opening of an {eta}{sup 3}-cyclobutenyl intermediate carrying an endo hydrogen, which becomes a pseudo-syn hydrogen on the terminus of the C{sub 4} chain.

Diphosphinonitrenium and ‐phosphenium Cations, Jahn‐Teller Distorted Allyl Systems

Ab initio calculations at SCF, MCSCF, and ACPF level were performed on a series of the phosphenium‐ and nitreniumcation family. These show that they possess an allylic π‐system with 4 electrons, which is distorted from planarity when the terminal groups of the allylic system are PR2 (R  H) fragments. The distortion is such as to adopt C2 symmetry, and is the consequence of Jahn‐Teller distortion via mixing of the energy highest π2 orbital with an energetically low lying δ* orbital. The latter interaction is only operative if a symmetry breaking from C2v to C2 symmetry occurs. The importance of Jahn‐Teller distortion on the biradical character in these systems is investigated by correlation calculations.