16644-98-7

Photoinduced oxygenation generates biologically active, oxidatively truncated lipids in the retina. Previously, doubly allylic dihydroperoxides, 9,12-dihydroperoxyoctadeca-10,13-dienoic acid (9,12-diHPODE) and 10,13-dihydroperoxyoctadeca-8,11-dienoic acid (10,13-diHPODE), were postulated as key intermediates in the free radical-promoted oxidative fragmentation of linoleate that generates aldehydes, such as the cytotoxic γ-hydroxyalkenal 4-hydroxy-2-nonenal (HNE), in vivo. We now report an efficient preparation of regioisomerically pure 9,12- and 10,13-diHPODE, devised to enable studies of their fragmentation reactions. Free radical-induced oxygenation of linoleate initially generates conjugated monohydroperoxy octadecadienoates (HPODEs) that are then converted into diHPODEs. In contrast, we found that singlet oxygenation of conjugated HPODEs does not produce diHPODEs. Unconjugated HPODEs are unique products of singlet oxygenation of linoleate that are coproduced with conjugated HPODEs. Preparative separation of the mixture of regioisomeric mono and diHPODEs generated by singlet oxygenation of linloeate is impractical. However, a simple tactic circumvented the problem. Thus, selective conversion of the undesired conjugated HPODEs into Diels-Alder adducts could be accomplished under mild conditions by reaction with N-phenyltriazolinedione. These adducts were readily removed, and the two remaining unconjugated HPODEs could then be easily isolated regioisomerically pure. Each of these was subsequently converted into a different, regioisomerically pure, diHPODE through further singlet oxygenation.

(9Z,11E)-Hexadeca-9,11-dienal (1) was identified as a major component of the sex pheromone of the sugarcane borer Diatraea saccharalis. The identification is based on mass spectral examination of the extracts prepared from calling females, derivatization experiments with 4-methyl-3,5-dihydro-1,2,4-triazole-3,5-dione (2), stereospecific synthesis of dienal 1, and gas chromatography (GC) with electroantennographic detection (GC-EAD). In GC analysis, the antennaly active component and synthetic dienal 1 show identical retention times on several GC phases. However, the behavioral activity of synthetic 1 was much weaker than that of natural extracts. This suggests that an additional component(s) might be involved in sexual communication of this species.

A synthetic method using tungsten-π-allyl compounds is developed for total syntheses of natural bislactones including (+)-dihydrocanadensaolide (2), (±)-avenociolide (3), and (±)-isoavenociolide (4). Syntheses of these natural compounds are based on a com

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(Z)-13-hexadecen-11-yn-1-yl acetate (2), the sex pheromone of Thaumetopoea pytyocampa, and (5Z,7E)-5,7-dodecadien-1-ol (3), sex pheromone component of Malacosoma disstria, have been prepared in high chemical and stereoisomeric purity by synthetic schemes involving the stereospecific coupling of ω-functionalized 1-alkynes with (Z)- or (E)-1-iodo-1-alkenes in the presence of a catalytic amount of (PPh3)4Pd and CuI, under phase transfer conditions.

Dibromoborane-dimethyl sulfide undergoes direct hydroboration of both terminal and internal alkynes with remarkable facility to give alkenyldibromoboranes.These reactive alkenylboranes, which may be isolated, undergo many synthetically useful transformations.Oxidation provides the carbonyl compounds, while protonolysis with acetic acid occurs stereospecifically to yield the corresponding alkenes. 1-Alkenyldibromoboranes can be converted easily to 1-iodo-1-alkenes by basic hydrolysis and iodination.Both internal and 1-alkenyldibromoboranes serve as convenient precursors to symmetrical conjugated dienes by reaction with 3 equiv of methylcopper.Hydroboration of alkynes with HBBr2*SMe2 is critically examined in terms of relative reactivities of both alkyne and alkene substrates.A very broad reactivity spectrum is evident, with internal acetylenes reacting with remarkable facility.The regiospecifity of the hydroboration of unsymmetrically substituted alkynes indicates HBBr2*SMe2 to be a highly selective reagent, sensitive to both steric and electronic effects.The regioselectivity is compared with that of other hindered hydroborating reagents, such as 9-BBN and disiamylborane.

We report palladium-catalyzed cross-coupling reactions of chiral secondary non-stabilized dialkylzinc reagents, prepared from readily available chiral secondary alkyl iodides, with alkenyl and aryl halides. This method provides α-chiral alkenes and arenes with very high retention of configuration (dr up to 98:2) and satisfactory overall yields (up to 76 % for 3 reaction steps). The configurational stability of these chiral non-stabilized dialkylzinc reagents was determined and exceeded several hours at 25 °C. DFT calculations were performed to rationalize the stereoretention during the catalytic cycle. Furthermore, the cross-coupling reaction was applied in an efficient total synthesis of the sesquiterpenes (S)- and (R)-curcumene with control of the absolute stereochemistry.

The first isolated examples of intermolecular oxidative addition of alkenyl and alkynyl iodides to AuI are reported. Using a 5,5′-difluoro-2,2′-bipyridyl ligated complex, oxidative addition of geometrically defined alkenyl iodides occurs readily, reversibly and stereospecifically to give alkenyl-AuIII complexes. Conversely, reversible alkynyl iodide oxidative addition generates bimetallic complexes containing both AuIII and AuI centers. Stoichiometric studies show that both new initiation modes can form the basis for the development of C?C bond forming cross-couplings.

A “one-shot” cross coupling between benzyl alcohols and alkenyl halides has been established. A combination of low-valent Ti-mediated C?OH homolysis and the prominent chemistry of Ni-based radical catalysis afforded the desired cross-coupled product with good efficiency. The reaction proceeded regardless of the electronic property of benzyl alcohols, and Ar?B bond remained intact throughout the reaction. Alkenyl bromides with various substitution patterns were applicable to this reaction. Attempts for utilizing sterically demanding tri-substituted alkenes indicated that the steric hinderance mainly inhibited the radical-trapping by Ni species. This reaction can be a simple and efficient strategy for synthesizing densely substituted allylbenzene derivatives. (Figure presented.).

Total synthesis of Debilisone C, a lactone containing conjugated endiyne has been achieved. The adopted strategy involves the stereoselective construction of the five membered lactone ring and the C20 endiyne chain followed by regioselective coupling of both the parts. The lactone was obtained from the oxidative cleavage of the hydroxy olefin which was derived from the benzyl protected S-epichlorohydrine by regioselective epoxide opening with allyl trimethyl silane in presence of a Lewis acid at -78 °C. Takai olefination, Pd0/Ag1 catalyzed cross-coupling reaction and selective substitution of trimethylsilyl groups were successfully utilized to establish the C20 polyyne chain. The final coupling of both the parts have been carried out by alkyl coupling using LDA in THF-DMPU (1 : 1).

Reactions of [Bu4N][RBF3] [R = CnF 2n+1CF=CF (cis, trans), CF2=CF, CF2=C(CF 3), trans-C4H9CF=CF, trans-C6H 5CF=CF, C4H9CH=CH (cis, trans), CF 3C≡C, and C4H9C≡C] with chlorine, bromine, BrF3 + Br2 (as equivalent of "BrF"), and ICl in solution (CH2Cl2, CHCl3, CF 3CH2CF2CH3) led to 1, 2-addition of halogen and/or replacement of boron by halogen (halodeboration). The reaction of [Bu4N][CF3C≡CBF3] with less than equimolar amounts of diluted fluorine (5 %) in 1, 1, 1, 3, 3-pentafluorobutane (PFB) showed only [Bu4N][CF3CF2CF 2BF3] as fluorine addition product besides extensive fluorodeboration. Suspensions of the insoluble K[CF2=CFBF 3] salt reacted with Cl2 and Br2 in CH 2Cl2 giving preferentially products of halogen addition across the C=C bond. In reactions with ICl iododeboration with formation of CF2=CFI occurred besides 1, 2-addition with formation of [CF 2I-CFClBF3]-. The halodeboration reaction of[Bu4N][trans-C4H9CF=CFBF3] with Br2, "BrF", and ICl, of K[trans-C6H 5CF=CFBF3] with Br2, and of [Bu 4N][trans-C4F9CF=CFBF3] with ICl proceeded stereospecifically. Copyright

A novel one-pot synthesis of 1,1-dihalo-1-alkenes and 1,1-bis(butyltelluro) -1-alkenes was developed from hydrozirconation of alkynylzinc bromide with Cp2Zr(H)Cl and subsequent capture of the Zn/Zr 1,1-heterodimetallo-1- alkene intermediates wi

The C-Si bonds of triisopropylsilyl-substituted alkenes, 1,3-dienes, and related multifunctional substrates, as well as analogous C-TBDPS and C-TBS bonds, are readily and chemoselectively cleaved with NIS (or other sources of I+, such as N-iodo

Treatment of (E)-alk-1-enyldicyclohexylboranes with tributyltin methoxide in the presence of galvinoxyl (1 mol%) at room temperature results in transfer of the alk-1-enyl group from boron to tin to give (E)-alk-1- enyltributylstannanes in a highly stereoselective fashion. Subsequent halodestannylation of (E)-alk-1-enyltributylstannanes is allowed to proceed in a one-pot manner to produce the corresponding (E)-1-iodoalk-1-enes and (E)-1-bromoalk-1-enes in good to high yields, respectively. Georg Thieme Verlag Stuttgart.

Both eight-membered enamide rings and fused [4.2.0]aminocyclobutane- containing δ-lactams can be accessed from N-vinyl-β-lactams. The eight-membered rings are made through a [3,3] sigmatropic rearrangement. At elevated temperature, the eight-membered lact

(Chemical Equation Presented) We describe a tandem Mitsunobu/3,3- sigmatropic rearrangement of allylic azides on a chiral auxiliary system that favors one regioisomer thanks to its exceptional steric bias. The sequence may be completed by the oxidative cleavage of the auxiliary or by a ring-closing metathesis reaction that produces a carbo-or heterocycle directly and a recyclable form of the chiral auxiliary. Applications of the methodology to the total synthesis of (+)-coniine, (+)-lentiginosin, and (+)-pumiliotoxin C are reported.

The Pd(0)-mediated rapid coupling of methyl iodide with an excess of alkenyltributylstannane was examined with the aim of incorporating a short-lived 11C-labeled methyl group into a biologically significant organic compound with a 1-methylalkene unit for the synthesis of a PET tracer. Four sets of reaction conditions (A-D) were used, all performed in DMF at 60 °C for 5 min. Condition B, using CH3I/stannane/Pd2(dba) 3/P(o-tolyl)3/CuCl/K2CO3 (1: 40: 0.5: 4-6: 2: 5), works well in almost all cases. Condition D, using CH 3I/stannane/Pd2(dba)3/P(o-tolyl) 3/CuX (X = Br, Cl, or I)/CsF (1: 40: 0.5-5: 2-20: 2-20: 5-50), shows the best results with regard to general applicability to tin substrates, affording the corresponding methylated product in >90% yield based on consumption of methyl iodide. P(t-Bu)2Me was less effective than P(o-tolyl)3, particularly for α,β-unsaturated carbonyl substrates. No regio- or stereoisomerization occurred under these reaction conditions. The efficiency of the protocol was demonstrated by synthesis of an 11C-methylated compound. The Royal Society of Chemistry 2006.

The carbocupration reaction of alkynyl carbamates leads to the stereospecific preparation of polysubstituted alkenyl carbamates. Subsequent treatment of these enol carbamates with the Negishi reagent gave the corresponding vinyl zirconocene species. Georg Thieme Verlag Stuttgart.

Reaction of alkenyl boronic acids with halosuccinimides (NIS, NBS or NCS) gives the corresponding alkenyl halides with the same geometry. This method is suitable for the synthesis of geometrically pure (E) and (Z) alkenyl halides, as well as 1,1- and 1,2-

Trans-alkenyl iodides are treated with tert-butyllithium in hexane at room temperature to provide pur trans-alkyllithiums in good yield.

(E)-1-iodo-1-alkenes 4 can be prepared stereoselectively from aldehydes 1 via IH-elimination of 1,1-di-iodoalkanes 3 with DBU. Key words: Vinyl iodide; diiodoalkane; elimination; stereoselectivity.

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Coupling reactions of lithium compounds, (Z)-carbonyl olefination of phosphonium ylides and 'crossed' Wittig olefination of bisylides are the key reaction steps in the synthesis principle for nonconjugated, bisolefinic Lepidoptera pheromones and structural analogs. Double unsaturated (E,Z)- and (E,E)-1-vinyl halides are converted into the corresponding (E,Z)- and (E,E)-1-vinyl lithium compounds and coupled selectively to (E,Z)- and (E,E)-alkadienols, alkadienals and alkadienyl acetates with different carbon chain length, geometry and relative positions of double bonds. 'Crossed' Wittig reactions of 1,ω-alkylidene bisylides with two different alkanals gives rise to the formation of corresponding (Z,Z)-dienic sex attractants and derivatives. A monounsaturated (E)-1-vinyl iodide is the synthon for the preparation of an (E)-alkenyl bromide which is converted to an (E)-alkenyl phosphonium salt and (Z)-selectively olefinated to (Z,E)-isomers of moth sex pheromones.

The previously unreported diiodomethylsodium has been prepared; its thermal stability as well as nucleophilc behaviour (alkylation leading to 1,1-diiodoalkanes and allylation leading either to 1,1-diiodo-3-alkenes or 1-iodoalkadiene) are described and compared with the corresponding reactions of the lithium carbenoid.Alternatively, both lithium and sodium derivatives of diiodomethane react as electrophiles with α-sulfonyl carbanions to give 1-iodoalkenes in good yield.

The relative reactivities of alkylmercury halides toward PhS., PhSe., or I. decrease drastically from R = tert-butyl to R = sec-alkyl to R = n-butyl, indicative that R. is formed in the rate-determining step in the attack of these radicals upon RHgCl.The alkyl radicals thus formed will enter into chain reactions in which a heteroatom-centered radical (A.) is regenerated from substrates such as RS-SR, ArSe-SeAr, ArTe-TeAr, PhSe-SO2Ar, Cl-SO2Ph; ZCH=CHA (A = Cl, I, SPh, SO2Ph); or PhCCHA (A = I, SPh, SO2Ph). β-Styrenyl (PhCH=CHA, Ph2C=CHA) and β-phenethynyl (PhCCA) systems with A = I, Br, SO2Ph also enter into chain reactions with mercury(II) salts with the ligands PhS, PhSe, PhSO2, or (EtO)2PO.The relative reactivities of a series of reagents toward t-Bu. and of PhCH=CHA, Ph2C=CHA, and PhCCA toward c-C6H11. are reported as well as the regioselectivity of t-Bu. attack observed for 1,2-disubstituted ethylenes (ZCH=CHA) with Z and A from the group Ph, Cl, Br, I, SO2Ph, SPh, Bu3Sn.Reactions of (E)- and (Z)-PhCH=CHI or MeO2CCH=CHI with t-Bu. or c-C6H11. occurred in a regioselective and stereospecific (retention) manner.Reactions of (E)- and (Z)-ClCH=CHCl occurred in a nonstereospecific manner in which the E/Z product ratio increased with the bulk of the attacking radical.A similar effect on the E/Z product ratios was observed for (Z)-MeO2CCH=CHCl.

A general and stereospecific synthesis of (Z)-disubstituted alkenes using mono- and dihaloboranes is presented.The hydridation of dialkylhaloboranes in the presence of 1-alkynes provides the corresponding dialkylvinylboranes (1), representing the first general synthesis of such derivatives.Treatment with iodine in the presence of sodium methoxide induces the migration of one of the alkyl groups from boron to the adjacent carbon, followed by a rapid deiodoboronation to afford (Z)-disubstituted alkenes (2) in high yields.Similarly, the hydroboration of 1-alkynes with alkyl bromoboranes (R1BHBr*SMe2, 4) followed by iodination in the presence of sodium methoxide in methanol affords (Z)-disubstituted alkenes (2) in good yields.Both procedures constitute a general one-pot synthesis of (Z)- disubstituted alkenes from an alkene and 1-alkyne.A simple synthesis of Muscalure (7), the sex pheromone of the housefly (Musca domestica), is achieved in good yields.An alternative general stereospecific synthesis of (Z)- and (E)-disubstituted alkenes based on alkenylboronic esters is also described.

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Several new methods for the preparation of vinyl iodides via mercuration and thallation reactions of vinylboronic acids have been explored.Chloramine-T oxidation of alkylvinylmercury iodides or iodide treatment of alkylvinylthallium trifluoroacetate substrates, prepared from the corresponding alkylvinylboronic acid and thallic trifluoroacetate, yields the corresponding alkylvinyl iodides.These method are also efficient for the synthesis of the corresponding radioiodinated compounds.

Alkenes and alkynes, which are normally inert to lithium borohydride, are readily hydroborated by this reagent in ethyl ether in the presence of carboxylic esters at 25 deg C.Alkenes form dialkylborinates while alkynes give rise either to vinylboranates or divinylborinates, depending upon the structure and reactivity of the alkyne and the stoichiometry of the reagent.This valuable intermediates are readily transformed into other organic derivatives, thus making this controlled hydroboration procedure a practical, valuable procedure in organic synthesis.

Lithium diorganocuprates add across the triple bond of substituted and non-substituted acetylenyl acetals and ketals to give dialkenylcuprates, which can be decomposed into alkoxyallenes or may be trapped with a variety of electrophiles, such as alkyl, alkenyl, alkynyl and aryl halides.They may also undergo conjugate addition to α-β unsaturated esters and ketons.The method is used for the synthesis of (+/-)-manicone, pure geranial and (E,Z)2,4-dienals.

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1,3,2-Benzodioxaborole readily hydroborates alkynes to form vinylboronic esters.The esters can be hydrolyzed to the corresponding vinylboronic acids which react with sodium iodide and chloramine-T to form isometrically pure (E)-iodoalkenes.

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