Efficient synthesis of cyclopentadienone derivatives by the reaction of carbon dioxide with 1,4-dilithio-1,3-dienes

One-pot reaction of carbon dioxide with 1,4-dilithio-1,3-diene derivatives afforded cyclopentadienone derivatives bearing various substituents in high yields within several minutes.     

Highly enantioselective catalytic carbon dioxide incorporation reaction: nickel-catalyzed asymmetric carboxylative cyclization of bis-1,3-dienes

A method for nickel-catalyzed asymmetric carbon dioxide (CO2) incorporation via carbon-carbon bond formation was developed. In the presence of a catalytic amount of Ni(acac)2 and MeO-MOP, various bis-1,3-dienes reacted with CO2 (1 atm) and a diorganozinc reagent (Me2Zn or Ph2Zn) to afford cyclic carboxylic acids in good yields (71-100%) and with high enantioselectivities (90-96% ee).     

Synthesis of long-chain polyketide fragments by reaction of 1,3-dioxy-1,3-dienes with allylsilanes: umpolung with sulfur dioxide

[reaction: see text] In the presence of a Lewis or protic acid and at low temperature, 1,3-dioxy-1,3-dienes add to sulfur dioxide generating zwitterionic intermediates that can react with carbon nucleophiles such as allylsilanes. After a retro-ene elimination of SO(2), valuable polyketide precursors are obtained.     

Efficient Synthesis of 1,3,5-Benzotriazocines from Tetrachloro-2-aza-1,3-dienes

Easily accessible 1-aryl-2-aza-1,3-butadienes undergo a regioselective cyclocondensation with 2-(aminomethyl)aniline, giving rise to 1,3,5-benzotriazocines in good yields. The structure of the title compounds was proved with the aid of ¹H and ¹³C NMR spectra and, in one case, single-crystal x-ray analysis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis of 1-nitro-1,3-dienes via nitrotrifluoroacetoxylation of 1,3-dienes

Nitrotrifluoroacetate adducts, obtained from 1,3-dienes by reaction with ammonium nitrate in trifluoroacetic anhydride, readily eliminate to afford 1-nitro-1,3-dienes in high yield.     

Nickel-catalyzed intermolecular coupling of 1,3-dienes and aldehydes via transmetalation of nickelacycles with diisobutylaluminum acetylacetonate

Intermolecular coupling reactions of 1,3-dienes and aldehydes via transmetalation of nickelacycle intermediate with (i)Bu(2)Al-acac were investigated. In the reactions, a linear adduct or a branched adduct was produced, depending upon the nature of 1,3-dienes and aldehydes, via two nickelacycles that were relatively stable among the four possible nickelacycles because of the equilibrium with pi-allynickel forms.     

New insights into the palladium-catalysed synthesis of δ-lactones from 1,3-dienes and carbon dioxide

Two-coordinate Pd(0) complexes are shown to be important intermediates in the telomerization of 1,3-dienes and CO₂ using palladium/phosphine catalysts without additives. Only one phosphorus atom is bound to palladium during the C–C bond forming steps, but the second phosphorus atom is crucial in the early stages of the catalytic cycle and for the elimination of the product. A ligand that gave an active palladium catalyst for the coupling of 1,3-butadiene and CO₂ has been designed. Use of a palladium catalyst in the reaction of isoprene with CO₂ allowed for the first time isolation and NMR spectroscopic characterization of the resulting mixture of lactones.     

Cross-metathesis of 1,3-dienes with electron-deficient olefins

Cross-metathesis reactions between 1,3-dienes and electron-deficient olefins have been investigated. Terminal monosubstituted 1,3-dienes afforded low yields of the desired CM products due to competing cleavage of the internal double bond. This undesired cleavage is successfully suppressed in the case of 1,3-dienes containing a sterically more congested internal double bond. Methyl vinyl ketone as the coupling partner was shown to provide the best yields.     

Polymerization of 1,3-dienes with neodymium catalysts

Neodymium catalysts are typical for the cis polymerization of 1,3-dienes. The systems prepared from a neodymium-carboxylate, a chlorine donor and A1(i-C₄H₉)₃ are characterized by a low efficiency, only ca. 6% of the neodymium being active in the catalysis. Much more active systems are obtained using allyl derivatives of neodymium in combination with aluminoxanes, in particular with methylaluminoxane (MAO). These systems have the characteristics of a single site catalyst. Evidence suggesting an ionic structure for the catalytic species is reported. Terminally substituted butadienes give polymers with a cis-1,4 isotactic structure, with the exception of (E, E)-2,4-hexadiene, which gives trans-1,4 polymers. An interpretation is reported.     

Cycloaddition reactions of 1,3-diazabuta-1,3-dienes with alkynyl ketenes

The cycloaddition reactions of ‘all-carbon’ 1,3-diazabuta-1,3-dienes with a few conjugated and unconjugated alkynyl ketenes are described. The reactions provide some interesting azetidinones and dihydropyrimidinones bearing an alkynyl moiety. The regiochemistry of cycloadduct is related with the degree of conjugation of the alkynyl ketene. Moreover, two alternative approaches to ‘all-carbon’ 1,3-diazabuta-1,3-dienes are reported.     

Nickel-catalyzed enantioselective three-component coupling of bis-1,3-dienes, aldehydes, and dimethylzinc

Nickel-catalyzed three-component coupling of bis-1,3-dienes, aldehyde, and dimethylzinc was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, bis-1,3-dienes smoothly react with an aldehyde and dimethylzinc via intramolecular cyclodimerization of bis-1,3-diene moiety. The reaction proceeds through formation of a cyclic bis-allylnickel complex, insertion of an aldehyde, and addition of dimethylzinc to the resulting oxanickellacycle intermediate. An enantioselective coupling was also achieved by the use of a chiral monodentate phosphine ligand, H-MOP.     

Diels-Alder reaction of methyl coumalate with 1,3-dienes

Reaction of methyl coumalate (1b) with 1,3-butadienes at 100° afforded the tetrahydrocoumarins (6) and the 4-methoxycarbonyltricyclo[3.2.1.0^2,7]octenes (7). The similar reaction of 1b with cyclohexadiene gave exclusively tetrahydronaphthalene-2-carboxylate. With cyclopentadiene, 1b afforded a product (10) resulting from the addition reaction in which cyclopentadiene acted as a dienophile. The reaction giving 6 is the first example of the reaction of a 2-pyrone as a dienophile.     

The reaction of phosphinyl radicals with 1,3-dienes

The stabilized radical, [(Me₃Si)₂CH]₂P·, reacts with 1,3-dienes to afford 1,4-diphosphino-2-butenes.     

Cobalt-catalyzed three-component coupling reaction of alkyl halides, 1,3-dienes, and trimethylsilylmethylmagnesium chloride

[reaction: see text] A combination of CoCl(2) and 1,6-bis(diphenylphosphino)hexane catalyzes a novel three-component coupling reaction of alkyl bromides, 1,3-dienes, and silylmethylmagnesium chloride, yielding homoallylsilanes in good to excellent yields. The reaction involves a radical species from alkyl halides.     

Efficient catalytic synthesis of optically active cyclic carbonates via coupling reaction of epoxides and carbon dioxide

Chiral Co(salen) complexes bearing the Lewis acid of group 13 can efficiently catalyze the reactions of carbon dioxide with epoxides in the presence of catalytic amounts of alkali metal salts, quaternary ammonium halide or ionic liquids. They exhibited excellent activity for producing enantiomerically enriched cyclic carbonates.     

Selenosulfonation of 1,3-dienes: One-pot synthesis of 2-(phenylsulfonyl)-1,3-dienes

A one-pot procedure for the transformation of a 1,3-diene into the corresponding 2-(phenylsulfonyl)-1,3-diene was developed. The reaction involves a 1,2-selenosulfonation-oxidation sequence.