Application of SDP Ligands for Pd‐Catalyzed Allylic Alkylation

Chiral spiro diphosphines (SDP) are efficient ligands for the Pd‐catalyzed asymmetric allylic alkylation of 1,3‐diphenyl‐2‐propenyl acetate with dimethyl malonate and related nucleophiles. The newly synthesized ligand DMM‐SDP ( 1e ) with 3,5‐dimethyl‐4‐methoxy groups on the P‐phenyl rings of the phosphine shows the highest enantioselectivity (up to 99.1% ee). Diethylzinc as a base is critical for obtaining high enantioselectivity in the allylic alkylation using β‐dicarbonyl nucleophiles. The structure of catalyst [PdCl₂((S)‐SDP)] was determined by single crystal X‐ray diffraction. The SDP ligands create an effective asymmetric environment around the palladium, resulting in high enantioselectivities for the asymmetric allylic alkylation reaction     

Phase‐Transfer‐Catalyzed Olefin Isomerization/α‐Alkylation of α‐Alkynylcrotonates as a Route for 1,4‐Enynes

The phase‐transfer‐catalyzed alkylation of α‐alkynylcrotonates was developed as a means to provide 1,4‐enynes deconjugated by an all‐carbon quaternary center. Extension to the asymmetric version using the chiral phase‐transfer catalyst (S)‐ 3 provided the alkylated compounds with up to 87% ee.     

Reaction pathways in the liquid phase alkylation of biomass‐derived phenolic compounds

Alkylation is a promising reaction for the upgrading of bio‐oil because it maximizes the retention of carbon in the liquid product. The alkylation of m‐cresol with isopropanol and HY zeolite was studied in a liquid phase system. The experimental results were fitted with two conventional surface kinetic models, Langmuir–Hinshelwood and Eley–Rideal, from which adsorption and rate constants were estimated. Two types of alkylation reactions were observed: C‐alkylation with formation of a C?C bond with the ring and O‐alkylation with formation of an ether bond with the hydroxyl group. It was concluded that O‐alkylation products do not undergo intramolecular rearrangement but first decompose into the corresponding phenolic. Alkylation occurs from both isopropanol and propylene, both of them yielding O‐and C‐alkylation to different extents. Isopropanol favors O‐alkylation while propylene favors C‐alkylation. Rate constants for multiple alkylation steps were progressively lower, suggesting the presence of steric hindrance during incorporation of additional isopropyl groups. © 2014 American Institute of Chemical Engineers AIChE J, 61: 598–609, 2015     

An Efficient and Recyclable Catalyst for N‐Alkylation of Amines and β‐Alkylation of Secondary Alcohols with Primary Alcohols: SBA‐15 Supported N‐Heterocyclic Carbene Iridium Complex

A mesoporous silica (SBA‐15)‐supported pyrimidine‐substituted N‐heterocyclic carbene iridium complex was prepared and used as a catalyst for both environmentally friendly N‐alkylation of amines and β‐alkylation of secondary alcohols with primary alcohols. The structure of the supported iridium catalyst was characterized by Fourier transform infrared (FT‐IR), ¹³C and ²⁹Si solid‐state nuclear magnetic resonance (NMR), small‐angle X‐ray scattering (SAXS), transmission electron microscopy (TEM), iridium K‐edge X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectroscopic analyses which demonstrated that the coordination environment of the iridium centre and the 3‐dimensional‐hexagonal pore structure of SBA‐15 were retained after the immobilization. The catalyst was found to be highly efficient for both kinds of reaction on a wide range of substrates under mild conditions. Moreover, the supported iridium catalyst was obviously superior to the unsupported one in the N‐alkylation of aniline and β‐alkylation of 1‐phenylethanol with benzyl alcohol as substrate, which indicated that not only the iridium complex moiety but also the support material contributed to the catalytic activity of the supported iridium catalyst in these reactions. The supported iridium catalyst can be easily recycled by simple washing without chemical treatment, and exhibited excellent recycling performance without notable decrease in catalytic efficiency even after twelve test cycles for N‐alkylation of aniline with benzyl alcohol, nine cycles for N‐alkylation of different amines with different alcohols, and eight cycles for β‐alkylation of 1‐phenylethanol with benzyl alcohol, respectively.     

Highly Enantioselective Copper‐Catalyzed Allylic Alkylation with Phosphoramidite Ligands

New phosphoramidites were applied as chiral ligands in the Cu‐catalyzed allylic alkylation with dialkylzinc reagents. A variety of substrates, reagents and chiral ligands were screened, resulting in improved catalytic methodology for allylic bromides in which enantioselectivities up to 88% were reached.     

Tuning of Regioselectivity in Inorganic Iodide‐Catalyzed Alkylation of 2‐Methoxyfurans via Electronic and Steric Effects

In the presence of inorganic iodide, the methoxy C O bond in 2‐methoxyfurans may be cleaved to afford the corresponding lactonic anion. Due to the presence of an electron‐withdrawing group at the 3‐position, the alkylation with normal organic iodides occurred at the 3‐position highly regioselectively. However, when electron‐deficient allylic iodides with an electron‐withdrawing group at the 2‐position were used the 5‐alkylation products were formed as the major products with sodium iodide as the catalyst. With magnesium iodide as the catalyst, the 5‐allylation occurred highly regioselectively. As a whole, the 3‐ vs. 5‐alkylation selectivity may be determined by the relative steric hindrance at the 3‐ and 5‐positions and the electronic effect of the allylic iodides. A rationale was proposed.     

Regiocomplementary O‐Methylation of Catechols by Using Three‐Enzyme Cascades

S‐Adenosylmethionine (SAM)‐dependent enzymes have great potential for selective alkylation processes. In this study we investigated the regiocomplementary O‐methylation of catechols. Enzymatic methylation is often hampered by the need for a stoichiometric supply of SAM and the inhibitory effect of the SAM‐derived byproduct on most methyltransferases. To counteract these issues we set up an enzyme cascade. Firstly, SAM was generated from l ‐methionine and ATP by use of an archaeal methionine adenosyltransferase. Secondly, 4‐O‐methylation of the substrates dopamine and dihydrocaffeic acid was achieved by use of SafC from the saframycin biosynthesis pathway in 40–70 % yield and high selectivity. The regiocomplementary 3‐O‐methylation was catalysed by catechol O‐methyltransferase from rat. Thirdly, the beneficial influence of a nucleosidase on the overall conversion was demonstrated. The results of this study are important milestones on the pathway to catalytic SAM‐dependent alkylation processes.     

Tris(acetylacetonato)rhodium(III)‐Catalyzed α‐Alkylation of Ketones, β‐Alkylation of Secondary Alcohols and Alkylation of Amines with Primary Alcohols

The tris(acetylacetonato)rhodium(III) catalyst is shown to be a versatile catalyst in the presence of DABCO (1,4‐diazabicyclo[2.2.2]octane) as ligand for the α‐alkylation of ketones followed by transfer hydrogenation, for the one‐pot β‐alkylation of secondary alcohols with primary alcohols and for the alkylation of aromatic amines in the presence of an inorganic base in toluene.     

Chemical modification of chloromethylated polystyrene with pyridylazo‐β‐naphthol

Chloromethylated polystyrene was chemically modified through alkylation of pyridylazo‐β‐naphthol (PAN) in the presence of a phase‐transfer catalyst. The chemical modification was achieved through O‐alkylation as well as N‐alkylation of PAN, leading to formation of polymer‐supported quaternary ammonium salt in the latter case. Both types of a polymer‐supported PAN moiety were detected by FTIR spectroscopic analysis. The complexation behavior of the polymer‐supported PAN as an ion‐exchanger toward some metal ions was studied. Thermogravimetric and differential thermogravimetric analyses data were used to study the kinetics of the thermal decomposition process of the ion‐exchanger. Some thermodynamic parameters for the ion‐exchanger were calculated by applying the rate theory of the first‐order reaction. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3044–3048, 2000     

Enantioselective Synthesis of α‐Amino‐γ‐sulfonyl Phosphonates with a Tetrasubstituted Chiral α‐Carbon via Quinine‐Squaramide‐Catalyzed Michael Addition of Nitrophosphonates to Vinyl Sulfones

α‐Nitro‐γ‐sulfonyl phosphonates with a key tetrasubstituted chiral α‐carbon center have been synthesized for the first time in high yield and enantioselectivity through a quinine‐squaramide‐catalyzed conjugate addition of α‐nitro phosphonates to aryl vinyl sulfones. Representative examples presented here for the transformation of nitrosulfonyl phosphonates to aminosulfonyl phosphonates, alkylation at the α‐position of the sulfonyl group followed by desulfonation and scale‐up of the conjugate addition highlight the practical applications of the methodology.     

Asymmetric Friedel–Crafts Alkylations of Indoles with Ethyl Glyoxylate Catalyzed by (S)‐BINOL‐Titanium(IV) Complex: Direct Access to Enantiomerically Enriched 3‐Indolyl(hydroxy)acetates

Enantioselective Friedel–Crafts alkylation reactions of a variety of indoles with ethyl glyoxylate, catalyzed by a chiral (S)‐BINOL‐Ti(IV) complex (10 mol %), are reported. The corresponding ethyl 3‐indolyl(hydroxy)acetates were formed in good yields and with high enantiomeric excess (up to 96 %). When methyl pyruvate or p‐chlorophenylglyoxal was used, the bisindole compound was obtained in excellent yield. A possible mechanism is proposed.     

Development of Diphenylamine‐Linked Bis(imidazoline) Ligands and Their Application in Asymmetric Friedel–Crafts Alkylation of Indole Derivatives with Nitroalkenes

The new diphenylamine‐linked bis(imidazoline) ligands were prepared through Kelly‐You’s imidazoline formation procedure mediated by Hendrickson’s reagent in good yields. The novel ligands were tested in the asymmetric Friedel–Crafts alkylation of indole derivatives with nitroalkenes. In most cases, good yields (up to 97%) and excellent enantioselectivities (up to 98%) can be achieved. The optimized bis(imidazoline) ligand with trans‐diphenyl substitution on the imidazoline ring gave better enantioselectivity than the corresponding bis(oxazoline) ligand.     

Enhancement of Propylene Production in a Downer FCC Operation using a ZSM‐5 Additive

The effects of high severity operation and ZSM‐5 addition on the FCC product yield distribution have been studied in a down‐flow reactor unit. VGO cracking at high reaction temperatures of 500–650 °C increases the yield of light olefins (propylene and butenes) with a corresponding loss in gasoline yield and increase in dry gas formation. Similar behavior is observed with the addition of 0–20 wt % ZSM‐5 additive, however, with no increase in dry gas. The combination of the two effects (high severity and ZSM‐5 addition) makes the FCC unit an excellent source of light olefins for downstream petrochemical and alkylation units. The novel process configuration increased the light olefin yield without significant loss in gasoline by suppressing thermal cracking reactions and dry gas formation.     

Preparation of SO42−/Fe2O3?MoO3 and its catalytic activity in the electrolytic reaction of phenol with methanol

BACKGROUND: Environmentally friendly solid catalysts are important in many processes from an industrial point of view and are applied widely in the study of alkylation of phenol with methanol in gas phase. However, liquid‐phase reactions have not been well studied. This paper deals with an assessment of liquid‐phase electrolytic alkylation in the presence of SO₄^2?/Fe₂O₃? MoO₃. RESULTS: A bidentate structure was formed between the SO₄^2? and metal. A catalyst with an amorphous structure delivered lower catalytic activity even at a higher Mo content. The highest activity was obtained at an Mo content of 16% (molar composition), which delivered a phenol conversion of up to 70.5%. Experiments also showed that the catalyst can be reused at least for three times. CONCLUSION: Application of solid catalyst in the liquid‐phase reaction assisted by electrolysis alkylation was found to be viable. The main products were methoxyphenols, in contrast to that associated with gas‐phase operation. A possible mechanism of product formation has been proposed. Copyright © 2008 Society of Chemical Industry     

Organocatalytic Asymmetric Vinylogous Michael Addition of Dicyanoolefins to Imine Intermediates Generated in situ from Arenesulfonylalkylindoles

An organocatalytic asymmetric vinylogous Michael addition of dicyanoolefins to vinylogous imine intermediates generated in situ from arenesulfonylalkylindoles has been developed. This protocol provides an easy and convenient approach to C‐3 alkyl‐substituted indole derivatives with high yields (up to 93%), diastereomeric ratios (up to 99:1 dr) and enantioselectivities (up to 99% ee). The resulting adducts can be also readily converted to pyrazolo derivatives or α‐alkylation products of ketones without any decrease of the diastereoselectivities and enantioselectivities.     

Organocatalytic Multiple Cascade Reactions: A New Strategy for the Construction of Enantioenriched Tetrahydrocarbazoles

A novel cascade Friedel–Crafts alkylation/Michael addition/aromatization reaction of 2‐vinylindoles with α,β‐unsaturated aldehydes has been developed for the construction of functionalized tetrahydrocarbazoles. The products were obtained in up to 97% yield and with excellent stereoselectivities (ee up to>99%, dr up to>99:1).     

Partially Hydrogenated 1,1′‐Binaphthyl as Ligand Scaffold in Metal‐Catalyzed Asymmetric Synthesis

Although chiral binaphthyl‐type ligands are already known to be effective over a broad spectrum of reactions, they sometimes fail in providing high enantioselectivities in some catalytic asymmetric reactions. This article summarizes recent attempts to elevate their performance by partly hydrogenating the naphthyl components of the binaphthyl. The synthetic routes to some of these ligands are briefly outlined. Positive results are observed in asymmetric hydrogenation, alkylation, borane reduction, epoxidation and hetero‐Diels–Alder reactions. The function of the partially reduced binaphthyl skeleton, however, can sometimes be disadvantageous or ambiguous as illustrated in reactions such as asymmetric ring‐closing metathesis, 1,4‐conjugate addition, epoxidation, allylic alkylation, trimethylsilylcyanation, epoxide ring‐opening and hydroformylation.     

固体酸催化莰烯与邻甲酚的选择性烷基化反应

详细考察了各类固体酸催化剂对莰烯与邻甲酚烷基化产物选择性的影响。采用气相色谱、气相色谱-质谱联用技术、核磁和红外表征了烷基化产物,并对结果进行了分析。实验结果表明:以丝光沸石为催化剂,用量为6%,莰烯与邻甲酚的物质的量的比为1∶1.5,反应温度为160℃,莰烯的转化率为99.89%,目标C—C烷基化产物的选择性可达77.48%。以脱铝丝光沸石、Al-HM为催化剂,莰烯的转化率分别达到99.36%、99.6%,目标C—C烷基化产物的选择性分别为77.57%和80.5%。     

Friedel‐crafts alkylation of diphenyl oxide with 1‐decene over sulfated zirconia as catalyst

Friedel‐Crafts alkylation and acylation reactions, using highly polluting homogeneous Lewis and Bronsted acids, are ubiquitous in a variety of organic process industries. In many cases very high conversions and selectivities can be achieved with aluminum chloride as catalyst and nitrobenzene as a solvent. However, environmental concerns associated with aluminum chloride‐nitrobenzene or BF3‐HF or mineral acids catalysts have encouraged development of solid acids, which not only intensify the rates of reactions but also offer better product selectivity. Amongst these catalysts, sulfated zirconia has gained a considerable importance due to its super‐acidity under certain conditions. The alkylation of diphenyl oxide with 1‐decene was studied over sulfated zirconia catalyst and it leads to industrially important products. The surface reaction between chemisorbed 1‐decene diphenyl oxide from the liquid phase, in the absence of any mass transfer resistance, was found to be the rate determining step with Eley‐Rideal type of mechanism.     

Highly Enantioselective Zinc‐Catalyzed Friedel–Crafts Alkylation of Indoles with Ethyl Trifluoropyruvate

A highly enantioselective Friedel–Crafts alkylation of indoles with ethyl trifluoropyruvate has been developed using N,N′‐dioxide‐zinc(II) complexes. Both enantiomers of the desired adducts were obtained by the use of enantiomeric ligands in excellent results (up to 99% yield and 98% ee) within 0.5 h under mild conditions. On the basis of the experimental results, a proposed working model was proposed to explain the origin of the asymmetric induction.