Direct benzylation and allylic alkylation in high-temperature water without added catalysts

In high-temperature water a series of benzyl and allylic alcohols reacted with 1,3-dicarbonyl compounds and activated aromatic compounds to give the alkylated products without added catalysts.     

Iodine-catalyzed allylation of 1,3-dicarbonyl compounds with allylic alcohols at room temperature

A highly efficient iodine-catalyzed allylation of 1,3-dicarbonyl compounds with a wide variety of allylic alcohols has been developed. The reaction is operationally straightforward and proceeds under very mild conditions at room temperature in good to excellent yields (up to 99%) and regioselectivity.     

Fluorinated alcohols as promoters for the metal-free direct substitution reaction of allylic alcohols with nitrogenated, silylated, and carbon nucleophiles

The direct allylic substitution reaction using allylic alcohols in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE) as reaction media is described. The developed procedure is simple, works under mild conditions (rt, 50 and 70 °C), and proves to be very general, since different nitrogenated nucleophiles and carbon nucleophiles can be used achieving high yields, especially when HFIP is employed as solvent and aromatic allylic alcohols are the substrates. Thus, sulfonamides, carbamates, carboxamides, and amines can be successfully employed as nitrogen-based nucleophiles. Likewise, silylated nucleophiles such as trimethylsilylazide, allyltrimethylsilane, trimethylsilane, and trimethylsilylphenylacetylene give the corresponding allylic substitution products in high yields. Good results for the Friedel-Crafts adducts are also achieved with aromatic compounds (phenol, anisole, indole, and anilines) as nucleophiles. Particularly interesting are the results obtained with electron-rich anilines, which can behave as nitrogenated or carbon nucleophiles depending on their electronic properties and the solvent employed. In addition, 1,3-dicarbonyl compounds (acetylacetone and Meldrum's acid) are also successfully employed as soft carbon nucleophiles. Studies for mechanism elucidation are also reported, pointing toward the existence of carbocationic intermediates and two working reaction pathways for the obtention of the allylic substitution product.     

Polymer-incarcerated gold-palladium nanoclusters with boron on carbon: a mild and efficient catalyst for the sequential aerobic oxidation-Michael addition of 1,3-dicarbonyl compounds to allylic alcohols

We have developed a polymer-incarcerated bimetallic Au-Pd nanocluster and boron as a catalyst for the sequential oxidation-addition reaction of 1,3-dicarbonyl compounds with allylic alcohols. The desired tandem reaction products were obtained in good to excellent yields under mild conditions with broad substrate scope. In the course of our studies, we discovered that the excess reducing agent, sodium borohydride, reacts with the polymer backbone to generate an immobilized tetravalent boron catalyst for the Michael reaction. In addition, we found bimetallic Au-Pd nanoclusters to be particularly effective for the aerobic oxidation of allylic alcohols under base- and water-free conditions. The ability to conduct the reaction under relatively neutral and anhydrous conditions proved to be key in maintaining good catalyst activity during recovery and reuse of the catalyst. Structural characterization (STEM, EDS, SEM, and N(2) absorption/desorption isotherm) of the newly prepared PI/CB-Au/Pd/B was performed and compared to PI/CB-Au/Pd. We found that while boron was important for the Michael addition reaction, it was found to alter the structural profile of the polymer-carbon black composite material to negatively affect the allylic oxidation reaction.     

Metal-free oxidative C-C bond formation of active methylenic sp C-H bonds with benzylic sp C-H and allylic sp C-H bonds mediated by DDQ

An efficient and simple method for the oxidative coupling of benzylic and allylic sp³ C-H bonds with active methylenic sp³ C-H bonds under metal-free conditions was developed by employing 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as an oxidant. The reaction was shown to proceed smoothly for various 1,3-dicarbonyl compounds with a range of benzylic and allylic substrates in good to excellent yields.     

Highly selective 1,3-isomerization of allylic alcohols via rhenium oxo catalysis

Two reaction strategies are developed to promote the highly selective 1,3-isomerization of a variety of allylic alcohols using O3ReOSiPh3 as a catalyst. The first strategy utilizes substrates whose 1,3-regioisomer contains a conjugated alkene, which relies on thermodynamics to obtain high selectivity. The second strategy employs N,O-bis(trimethylsilyl)acetamide as an additive to selectively and irreversibly remove the product from the reaction equilibrium and works well for the isomerization of tertiary allylic alcohols into primary allylic alcohols containing trisubstituted alkene components. High stereoselectivity is also observed in the 1,3-isomerization of enantioenriched allylic alcohols.     

可循环利用硅胶吸附三氯化铈-碘化钠催化1,3-二酮的 烷基化无溶剂反应

在无溶剂条件下, 硅胶吸附的水合三氯化铈-碘化钠(CeCl3?7H2O-NaI)可以作为路易斯(Lewis)酸有效催化活泼亚甲基化合物和烯丙醇的直接烷基化反应, 得到较高产率的烷基化产物(62%～90%). 该催化剂经过简单处理至少可以循环利用四次, 第四次循环后产率达到78%.     

Yb[N(SO2C8F17)2]3-catalyzed allylation of 1,3-dicarbonyl compounds with allylic alcohols in a fluorous biphase system

Allylation of 1,3-dicarbonyl compounds with allylic alcohols was successfully accomplished using rare earth metal (III) bis(perfluorooctanesulfonyl)imide [RE(NPf₂)₃, RE = La∼Lu] as catalysts in fluorous solvents. Ytterbium bis(perfluorooctanesulfonyl)imide [Yb(NPf₂)₃] catalyzes the high efficient reaction of allylation in fluorous solvents. By simple separation, fluorous phase containing only catalyst can be reused several times.     

Photoredox-Catalyzed Isomerization of Highly Substituted Allylic Alcohols by C−H Bond Activation

Photoredox-catalyzed isomerization of γ-carbonyl-substituted allylic alcohols to their corresponding carbonyl compounds was achieved for the first time by C−H bond activation. This catalytic redox-neutral process resulted in the synthesis of 1,4-dicarbonyl compounds. Notably, allylic alcohols bearing tetrasubstituted olefins can also be transformed into their corresponding carbonyl compounds. Density functional theory calculations show that the carbonyl group at the γ-position of allylic alcohols are beneficial to the formation of their corresponding allylic alcohol radicals with high vertical electron affinity, which contributes to the completion of the photoredox catalytic cycle.     

Highly selective methanesulfonic acid-catalyzed 1,3-isomerization of allylic alcohols

Secondary and tertiary allylic alcohols undergo 1,3-isomerization smoothly in the presence of methanesulfonic acid under simple and efficient conditions to afford selectively the corresponding primary E-allylic alcohols in excellent yields.     

Gold(III)-catalyzed direct nucleophilic substitution of propargylic alcohols

Gold-catalyzed nucleophilic substitution of propargylic alcohols with various nucleophiles (allylsilane, electron-rich aromatics, alcohols, thiols, hydrides, 1,3-dicarbonyl derivatives, sulfonamides) is described under very mild conditions (room temperature in dichloromethane). Preliminary mechanistic investigations suggest a mechanism through a carbocation intermediate. Nucleophilic substitutions on allylic and benzylic alcohols are also described.     

Allylic activation across an Ir–Sn heterobimetallic catalyst: nucleophilic substitution and disproportionation of allylic alcohol

A nucleophilic substitution of allylic alcohols with carbon (arene, heteroarene, allyltrimethylsilane, and 1,3-dicarbonyl compound), sulfur (thiol), oxygen (alcohol), and nitrogen (sulfonamide) nucleophiles has been demonstrated using an in house developed [Ir(COD)(SnCl₃)l(μ-Cl)]₂ heterobimetallic catalyst in 1,2-dichloroethane to afford the corresponding allylic products in moderate to excellent yields. In 4-hydroxycoumarin, allylation occurs at the 3-position. The diaryl-substituted allylic alcohols undergo disproportionation in presence of the heterobimetallic catalyst to provide the corresponding alkenes and chalcones. An electrophilic mechanism is proposed from Hammett correlation study.     

Metal oxo complexes as catalysts for the isomerisation of allylic alcohols

The 1,3-allylic rearrangement of allylic alcohols is an important transformation in organic synthesis and various methods for effecting such a transposition have been reported. This short review will focus on the development of transition metal oxo complexes as catalysts for the isomerisation of allylic alcohols. Mechanistic investigations are also discussed.     

Direct palladium/carboxylic acid-catalyzed C-allylation of cyclic 1,3-diones with allylic alcohols in water

The direct activation of C-O bonds in allylic alcohols in water as a suspension medium by palladium complexes has been accelerated by carrying out the reactions in the presence of a carboxylic acid. The palladium-catalyzed allylation of cyclic 1,3-diones using allylic alcohols directly gave the corresponding C-allylated products in good yields.     

Heteropoly acid-catalyzed highly efficient alkylation of 1,3-dicarbonyl compounds with benzylic and propargylic alcohols

Various 1,3-dicarbonyl compounds reacted readily with benzylic and propargylic alcohols in the presence of 10 mol % of phosphomolybdic acid supported on silica gel (PMA/SiO₂) under mild reaction conditions to produce 2-benzylic- and 2-propargylic-1,3-dicarbonyl compounds in excellent yields and with high selectivity.     

Yb(OTf)3-promoted effective benzylation and allylation with N-tosyl amino group as a stable leaving group

A simple, inexpensive, environmentally friendly, and highly efficient benzylation and allylation of 1,3-dicarbonyl compounds with sulfonamides in the presence of Yb(OTf)₃ is described. Yb(OTf)₃ was proved to be a good catalyst for the cleavage of sp³ carbon–nitrogen bond. Various 1,3-dicarbonyl compounds can couple with a broad range of tosyl-activated benzylic and allylic amines to give diversely functionalized products in good to excellent yields.     

Ruthenium-catalyzed redox isomerization of trifluoromethylated allylic alcohols: mechanistic evidence for an enantiospecific pathway

Transfer news: A synthetic approach to chiral β-CF(3)-substituted saturated carbonyl compounds has been developed in which ruthenium complexes efficiently catalyze the redox isomerization of CF(3)-bearing allylic alcohols by an intramolecular suprafacial enantiospecific 1,3-hydrogen transfer (see scheme). This method was used for the enantioselective synthesis of (S)-CF(3)-citronellol.     

Gold-catalysed allylic alkylation of aromatic and heteroaromatic compounds with allylic alcohols

Friedel-Crafts allylic alkylation of a wide variety of aromatic and heteroaromatic compounds with allylic alcohols catalysed by AuCl(3) (5 mol%) under mild conditions at room temperature was accomplished in good to excellent yields (up to 99%) and regioselectivity.     

The Heck-type arylation of allylic alcohols with arenediazonium salts

The Heck coupling of ArN₂BF₄ with secondary allylic alcohols, carried out in methanol using Pd(dba)₂ as catalyst without extra ligands and base, leads to the corresponding β-arylated carbonyl compounds. Such conditions afford arylated acetals from primary allylic alcohols.     

Palladium-catalyzed alkylation of vinyl oxiranes with substituted allenes. Direct access to bifunctionalized allylic alcohols

The first palladium-catalyzed alkylation of vinyl oxiranes with substituted allenes to form functionalized allylic alcohols is described. The reaction of activated allenes 5 with vinyl oxiranes 1 in the presence of catalytic amounts of Pd(PPh(3))(4) (10 mol %) and 1,3-bis(diphenylphosphino)propane (dppp) (20 mol %) in THF at 60 degrees C gave the corresponding allylic alcohols 6 in good to excellent yields. The allylic alcohols were obtained in different ratios of trans/ cis isomers.