Epoxidation of olefins by β-bromoalkoxydimethylsulfonium ylides

Olefins can be converted to their respective epoxides in a one-pot procedure by dissolving the olefin in anhydrous DMSO, adding NBS to the reaction mixture to generate a β-bromoalkoxydimethylsulfonium ylide, and then adding DBU to the reaction mixture. A large variety of alkenes were successfully epoxidized with yields largely dependent on the structure of the alkene. Most importantly, the facial selectivity of this one-pot process is the opposite of that observed when using traditional epoxidizing reagents. Electron-poor alkenes are not epoxidized under these conditions.     

Aminoselenenylation of olefins. Syntheses of β-phenylseleno carbamates

(β-Phenylseleno carbamates have been synthesized by reaction of olefins with phenylselenenyl chloride and carbamates in presence of silver tetrafluoroborate. This reaction constitutes a good method for the conversion of olefins to β-functionalized protected amines.     

Review of Directly Producing Light olefins via CO Hydrogenation

Directly making light olefins via CO hydrogenation is a promising process to obtain a nonpetroleum based supply of alkenes.Limited by the ASF distribution function of Fischer-Tropsch synthesis,the yield of light olefins (C2-C4) can not reach the desired levels,which is a great challenge to overcome.Beginning thermodynamic analysis,the ASF distribution function,the reaction performance of CO hydrogenation and slurry reactor studies.The problems currently faced by this research area are presented at the end of the article.     

Hydroformylation of olefins produced in the Fischer—Tropsch synthesis

Russian Chemical Bulletin - Alcohols were obtained by the one-stage hydroformylation of olefins from the hydrocarbon fraction C6–C9, which was produced in the Fischer—Tropsch synthesis...     

Selective reduction of α,β-unsaturated esters in the presence of olefins

Several α,β-unsaturated esters containing also isolated olefins or other functionalities subject to saturation were selectively reduced to the corresponding saturated esters by magnesium in methanol.     

Synthesis of keto acids from olefins andω-chloroformyl carboxylic esters

Summary The following were synthesized for the first time by the catalytic method from the corresponding alkene and acid chloride; 1) 6-oxo-7-decenoic acid; 2) 8-methyl-6-oxo-7-nonenoic acid; 3) 4-oxodecanoic acid; 4) 6-oxododecanoic acid; 5) 7,7,8-trimethyl-6-oxo-8-nonenoic acid; 6) 7,7,8-trimethyl-6-oxononanoic acid; 7) 6-oxotridecanoic acid (this acid was prepared previously by organomagnesium synthesis [4]).     

Hydroformylation of nitrogen-containing cyclic olefins via “in-situ” rhodium-phosphine catalysts

Hydroformylation of nitrogen-containing cyclic olefins (N-substituted nortropidines, N-methyl-1,2,3,6-tetrahydropyridine (THP) with rhodium-PR₃ catalysts prepared “in situ” is reported. The nortropidines reacted rapidly when either trialkyl- or triaryl-type phosphines were used, and the regioselectivities were not significantly influenced by the nature of the phosphine. With the less basic THP the rates and selectivities were generally lower, and were influenced by the phosphine ligand and by the presence of added bases such as Et₃N.     

Theoretical and experimental investigations of the enantioselective epoxidation of olefins catalyzed by manganese complexes

The enantioselective epoxidation of olefin by Mn^II（R,R-PMCP）(OTf)2, H₂O₂ and H₂SO₄ was explored by DFT calculations and experiments. Theoretical results suggest that [MnV（O）(R,R-PMCP)（SO4）]+species with a triplet ground spin state serves as the active species for the olefin epoxidation. It can be generated by the H₂SO₄ assisted O-O heterolysis of Mn^III（OOH） species. Mn^III-persulfate is also involve...     

Copper-catalyzed regioselective allylic oxidation of olefins via C–H activation

A regioselective oxidation of allylic C–H bond to C–O bond catalyzed by copper (I) was developed with diacyl peroxides as oxidants. The oxidation of allylic C–H bond was accomplished with good yield and regioselectivity under mild reaction conditions. This method has a broad substrate scope including cyclic olefins, terminal and internal acyclic olefins and allyl benzene compounds. The reaction proceeds by a radical mechanism as suggested by spin trapping experiments.     

Asymmetric hydrocyanation of olefins catalyzed by chiral diphosphite–nickel complexes

Chiral aryl diphosphite ligands derived from binaphthol were found to be effective in the nickel-catalyzed hydrocyanation of a variety of olefins. Enantioselective hydrocyanations of styrene, 4-substituted styrenes and norbornene were achieved with excellent regioselectivity and moderate enantioselectivity. The hydrocyanation of vinyl acetate gave 72.9% ee. The catalytic activity and the enantioselectivity of the Ni(0)–diphosphite complexes were found to be highly dependent on the structures of the ligands.     

Enantioselective Pd-catalyzed hydrogenation of tetrasubstituted olefins of cyclic β-(arylsulfonamido)acrylates

Asymmetric hydrogenation of tetrasubstituted olefins of cyclic β-(arylsulfonamido)acrylates produces the corresponding cyclic β-(arylsulfonamido)propionates using Pd(OCOCF₃)₂/diphosphine complexes as catalysts in the presence of TFA with up to 96% ee.     

Cross-metathesis of allyl halides with olefins bearing an α-alkoxy amide group

We have examined whether the allyl halide cross-metathesis reaction tolerates α-alkoxy amide groups. Ruthenium-based catalysts I-III did not catalyze the cross-metathesis of allyl halides in the presence of an α-alkoxy N,N-dimethylamide group to any appreciable extent, but the reaction could tolerate either a bulky N,N-diisopropylamide or Weinreb amide group. In particular, the Grubbs-Hoveyda-Blechert 2nd generation catalyst (III) efficiently catalyzed the cross-metathesis of allyl halides with olefins bearing a Weinreb amide group.     

Enantioselective oxysulfenylation and oxyselenenylation of olefins catalyzed by chiral Brønsted acids

This paper describes Brønsted acid catalyzed enantioselective oxysulfenylation and oxyselenenylation of olefins. Enantiomerically enriched tetrahydrofurans are formed with up to 63% ee with dibenzoyl-d-tartaric acid and its derivatives as catalyst. Chiral β-carboxyl sulfides and selenides have also been obtained with up to 50% and 84% ee, respectively, via enantioselective desymmetrization of thiiranium and seleniranium ions in the presence of catalytic amounts of chiral binaphthol derived N-triflyl phosphoramide.     

Reactions of cis-silyl tin olefins: (Anti-Denmark) nazarov cyclization of β-silyl divinyl ketones

Readily available silyl tin olefins efficiently couple with acid chlorides (Stille Reaction) to give β-silyl divinyl ketones. These ketones with large silyl groups (Et₃Si, t-BuMe₂Si) undergo Nazarov cyclizations wherein the silicon group is retained in the product.     

Living cationic polymerization of olefins. How did the discovery come about?

The tortuous road to living carbocationic polymerizations is chronicled. The impetus for this project was my conviction that, just as living anionic polymerizations have started with a critical insight, a similar breakthrough will also be possible with cations. Upon retrospect, the facts show a three-step progression to the objective: Discovery of 1) controlled initiation, 2) reversible termination (quasiliving systems), and 3) controlled chain transfer. But what good is the discovery of a process without demonstrating its usefulness in terms of desirable products? Thus, a section concerns unique microarchitectures obtainable only by this technique: functional liquids, telechelics, thermoplastic elastomers, etc. The marketing of some of these products has already started, and the fundamental exploration of the promises of this technique is in progress worldwide. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2285–2293, 1999     

The reaction of nitroso oxides with olefins: Concerted or nonconcerted addition?

The mechanism of the interaction of nitroso oxides (RNOO) with olefins was studied at MCQDPT2/6-311+G(3df, 2p)//CASSCF(10; 9)/6-311G(d) level of theory. The following reaction channels were considered: (1) (3 + 2)-cycloaddition and nonconcerted biradical addition of nitroso oxide (2) through the terminal oxygen atom and (3) through the nitrogen atom to the C=C multiple bond. It was shown for the cases of (A) cis/trans-HNOO + C₂H₄, (B) cis/trans-HNOO + C₂F₄, (C) cis/trans-PhNOO + C₂H₄, and (D) cis/trans-PhNOO + C₂H₃CH₃ model systems that the typical reaction of nitroso oxides with alkenes was cycloaddition. For olefins with a decreased electron density at the multiple bond, as in system B, a substantial contribution of the one-center mechanism with the formation of biradical intermediates is possible.     

Selective hydroformylation–acetalization of various olefins using simple and efficient Rh-phosphinite complex catalyst

A simple and efficient Rh-phosphinite complex catalyst was studied for the selective hydroformylation of various olefins. The influence of various reaction parameters including the effect of temperature, pressure, catalyst loading, time, and solvents was studied. The protocol was also applied for the synthesis of various acetals via tandem hydroformylation–acetalization of olefins in alcohols as solvents. High activity and selectivity for acetal formation was achieved in the absence of co-catalysts with admirable substrate to catalyst mole ratio (TON 2500). The developed protocol works for a wide range of olefins to synthesize corresponding aldehydes and acetals under optimized reaction conditions.     

Asymmetric epoxidation of olefins by chiral dioxiranes generated in situ from ketones of d-(−)-quinic acid

The in situ generated dioxiranes (Caroate as peroxide source) of the optically active ketones 4a and 4b, which may be conveniently prepared from d-(−)-quinic acid, serve as effective oxidants for the asymmetric epoxidation (ee values up to ca. 90% with 4a) of prochiral olefins.     

Synthesis of imine–amine type of chiral ligands and their application in the asymmetric cyclopropanation of olefins with diazoacetates

Novel chiral ligands 1, which possess both imine and amine moieties, were prepared from readily available homochiral materials. Copper complexes of 1 were prepared in situ and used in the asymmetric cyclopropanation of olefins with alkyl diazoacetates to give cyclopropanecarboxylates, inducing e.e. values of up to 87%. The size of the chelate ring in the copper complexes influenced the enantioselectivity of the reaction.