Synthesis of arylallenes by palladium-catalyzed retro-propargylation of homopropargyl alcohols

Treatment of tertiary homopropargyl alcohol with aryl halide under palladium catalysis provided arylallenes regioselectively. The reaction includes retro-propargylation, which proceeds in a concerted fashion via a cyclic transition state and transfers the stereochemistry of homopropargyl alcohols through C-C bond cleavage. The present method enables the use of homopropargyl alcohols as allenylmetal equivalents.     

锡-铟促进和微波辐射辅助下醛和炔丙基溴的炔丙基化反应

A rapid and regioselective preparation of homopropargyl alcohols was reported. In the presence of SnCl2C6HsMe3NBr and microwave irradiation, the mixture of tin-indium and propargyl bromide reacted quickly with aldehydes in aqueous media to produce the homopropargyl alcohols exclusively in high yields. For benzaldehydes bearing different substituents, electronic effect of the substituents affected the reaction, the electron-withdrawing groups promoting the reaction and the electron-donating groups impeding the reaction. The reactions of benzaldehydes bearing an ortho substituent group on the phenyl ring with propargyl bromide may yield a mixture of regioisomers （homopropargyl and homoallenyl alcohols） or a single homoallenic alcohol due to the steric effect.     

Intramolecular hydrosilation of acetylenes: Regioselective functionalization of homopropargyl alcohols

Platinum-catalyzed intramolecular hydrosilation of hydrodimethylsilyl ethers of homopropargyl alcohols proceeds regioselectively in a 5-exo-dig mode. The resulting vinylsilanes can be transformed into 3-alkanon-1-ol and 3-bromo-3-alken-1-ol derivatives by H₂O₂ oxidation and bromine cleavage, respectively.     

Stereoselective synthesis of optically active cyclopenta[c]pyrans and cyclopenta[c]furans by the intramolecular Pauson–Khand reaction

An intramolecular Pauson–Khand reaction of enynes derived from homoallyl, homopropargyl, and allyl alcohols is described. 2-Heteroaryl-substituted homoallyl, homopropargyl, and allyl alcohols are easily and efficiently resolved through enzymatic resolution in high ee (91–99%) and with a known stereochemistry. Each enantiomerically enriched enyne derived from homoallyl and homopropargyl alcohols affords the conformationally most stable diastereomeric cyclopenta[c]pyran ring system as the sole product, whereas enantiomerically enriched enynes derived from allyl alcohols give a diastereomeric cis:trans mixture of the cyclopenta[c]furan ring system.     

Chemoenzymatic route to various spirocyclic compounds based on enantiomerically enriched tertiary allylic,homoallylic, and homopropargylic alcohols

A ring closing metathesis (RCM) reaction of dienes and an intramolecular Pauson–Khand (PKR) reaction of enynes derived from tertiary allyl, homoallyl, and homopropargyl alcohol backbones to afford the corresponding spirocyclic dihydrofuran and dihydropyrans and spirocyclic cyclopentenone pyrans, respectively, are described. Cyclopent-2-ene anchored tertiary allyl, homoallyl, and homopropargyl alcohols 1a–c have been efficiently resolved via enzymatic resolution with high ee (up to 90%) with 44%, 40%, and 43% chemical yields, respectively. Moreover, the cyclohex-2-ene anchored tertiary allyl, homoallyl, and homopropargyl alcohols 3a–c have also been resolved in the same manner with high ee (up to 97%) and in 42%, 45%, and 49% chemical yields. Enantiomerically enriched dienes derived from tertiary homoallyl alcohols yield the corresponding enantiomerically enriched spirocyclic dihydropyran derivatives via RCM with 74% and 78% chemical yields and with 90% and 97% ee, respectively. Moreover, enantiomerically enriched enynes derived from tertiary homoallyl alcohols afford the corresponding enantiomerically enriched cyclopentenone pyrans with spirocyclic motifs via PKR with 80% and 81% chemical yields, respectively, and as single diastereomers.     

Lead-promoted Barbier-type reaction of aldehydes with propargyl bromides in aqueous media

This paper reports that the reaction of the propargyl bromides with aldehydes promoted by powdered lead in aqueous media.The selectivity and possible mechanism of these reactions are discussed.The yields of products for reaction of propargyl bromide are 31~71%.The ratios of al-lenyl alcohol and homopropargyl alcohol are 1:1.5 to 1:3.The product for reaction of phenyl propargyl bromide is allenyl alcohol and the yields are 52~84%.     

Novel Pd/C-catalyzed redox reactions between aliphatic secondary alcohols and ketones under hydrogenation conditions: application to H-D exchange reaction and the mechanistic study

A liquid-phase redox system between secondary alcohols and ketones is described. Deuteration of either secondary alcohols or ketones using the Pd/C-H2-D2O system gave a mixture of deuterium-labeled secondary alcohols and ketones. The results indicated that the secondary alcohol was oxidized to the corresponding ketone without oxidants under the hydrogenation conditions and the hydrogenation of the aliphatic ketone to the corresponding secondary alcohol simultaneously proceeded. Detailed mechanistic studies on the redox system as well as the H-D exchange reaction are discussed.     

Silver-catalyzed one-pot synthesis of arylnaphthalene lactones

Arylnaphthalene lignan lactones are valuable natural products with promising anticancer and antiviral properties. In an effort to simplify their synthesis, we investigated a one-pot multicomponent coupling reaction between phenylacetylene, carbon dioxide, and 3-bromo-1-phenyl-1-propyne. After the corresponding 1,6-diyne was generated in situ, cyclization afforded the desired product. The level of regioselectivity was enhanced through the tuning of electronic properties. The use of cinnamyl bromide which led to the formation of a 1,6-enyne intermediate was also studied.     

Highly efficient redox isomerization of allylic alcohols at ambient temperature catalyzed by novel ruthenium-cyclopentadienyl complexes--new insight into the mechanism

A range of ruthenium cyclopentadienyl (Cp) complexes have been prepared and used for isomerization of allylic alcohols to the corresponding saturated carbonyl compounds. Complexes bearing CO ligands show higher activity than those with PPh3 ligands. The isomerization rate is highly affected by the substituents on the Cp ring. Tetra(phenyl)methyl-substituted catalysts rapidly isomerize allylic alcohols under very mild reaction conditions (ambient temperature) with short reaction times. Substituted allylic alcohols have been isomerized by employing Ru-Cp complexes. A study of the isomerization catalyzed by [Ru(Ph5Cp)(CO)2H] (14) indicates that the isomerization catalyzed by ruthenium hydrides partly follows a different mechanism than that of ruthenium halides activated by KOtBu. Furthermore, the lack of ketone exchange when the isomerization was performed in the presence of an unsaturated ketone (1 equiv), different from that obtained by dehydrogenation of the starting allylic alcohol, supports a mechanism in which the isomerization takes place within the coordination sphere of the ruthenium catalyst.     

A FACILE SYNTHESIS OF 3-GLYCOSYL-5-SUBSTITUTED-2-ISOXAZOLES

The 1,3-dipolar cycloaddition reaction between a 2-deoxy-D-aldose oxime (D-gluco or D-ribo) and an alkyne as dipolarophile (phenylacetylene, 2-propyn-1-ol, 3-chloro-1-propyne, or 3-bromo-1-propyne) is described. The new 3-glycosyl-5-substituted-2-isoxazoles are characterized physically and spectroscopically.     

Pd(OAc)2/dppf as an efficient and highly active catalyst for the allylation of amines, alcohols and carboxylic acids with 1-phenyl-1-propyne

Pd(OAc)₂/1,1′-bis(diphenylphosphino)ferrocene as an efficient, highly active catalyst for the allylation of amines, alcohols and carboxylic acids with 1-phenyl-1-propyne has been developed. The effect of various reaction parameters, such as ligand, time, solvent, temperature, metal: ligand ratio and catalyst concentration on yields of the product were investigated. The optimized procedure works well under mild operating conditions and permits rapid generation of a library for various allylated products.     

新型离子液体的合成及其在Heck反应合成烯丙醇类化合物中的应用

以甲基咪唑（或咪唑）和N-取代芳基-3-氯丙酰胺为原料,与KPF-6经离子交换制得6个新型酰胺基功能化离子液体（2a～2c和3a~3c）。以2-溴-6-甲氧基萘与烯丙醇反应为模板反应,2或3为反应介质,考察反应的转化率和区域选择性。结果表明： 3为反应介质时,转化率和区域选择性均高于2。以溴代芳烃和烯丙醇为原料,3c为反应介质,醋酸钯催化Heck反应制得2-取代芳烃烯丙醇化合物,收率85%~89％,立体选择性均大于99%。所得产物的结构均经¹H NMR, ¹³C NMR, IR, EI-MS和元素分析表征。     

One-pot, solvent-free regioselective addition reactions of propargyl bromide to carbonyl compounds mediated by Zn-Cu couple

A Barbier-type propargylation of carbonyl compounds with propargyl bromide has been achieved with reactive zinc-copper couple under solvent-free conditions. The reaction of aldehydes with propargyl bromide produced the unique homopropargyl alcohols in excellent yields at room temperature without the formation of homoallenyl alcohols. The ketones reacted with propargyl bromide to give the corresponding homopropargyl alcohols in good to excellent yields at −14 to −16 °C. The advantages of this method are excellent yields, short reaction time, high regioselectivity, and avoidance of the use of organic solvents.     

乙酸镍吡啶配合物催化的分子氧氧化反应研究

Ni(OAc)2结合吡啶和叔丁基过氧化氢(TBHP)实现了苄基C-H与苄基醇类化合物在温和条件下(80～90℃,O21 atm)的选择性催化分子氧氧化反应.研究了过氧化物添加剂,配体,溶剂和温度的影响,得到了优化的反应条件.在苄基C-H的氧化中显示了很高的酮/醇选择性.用ESR法进行了Ni(III)的检测,证实了反应机理.竞争实验说明羰基化合物的生成不是因为醇继续氧化.酮可被解释为过氧化氢中间体受金属催化分解的产物.     

The polymerization of 3-chloro-1-propyne and 3-bromo-1-propyne with Mocl5 and WCL6 based initiators and the structure of the resulting polymers

The WCl₆ and MoCl₅ initiated polymerizations of 3-chloro-1-propyne and 3-bromo-1-propyne were performed in both halogenated and aliphatic non-nucleophilic and in aromatic nucleophilic solvents. The structure of the obtained polymers suggested that the polymerization reaction occurs in two steps. In both nucleophilic and non-nucleophilic solvents, the first step consists of the metathesis polymerization of 3-chloro(bromo)-1-propyne followed by electrophilic cis–trans isomerization leading to polymers containing trans-cisoidal allyl chloride or bromide structural units. When the polymerization is performed in non-nucleophilic solvents, in the second step an intramolecular electrophilic addition followed by elimination takes place. The resulting polymers contain a highly conjugated cyclopentadiene ladder structure. When the polymerization is performed in nucleophilic aromatic solvents, the intramolecular electrophilic addition competes with the electrophilic substitution of the solvent resulting in polymers containing high concentrations of arylpropenyl structural units. Subsequently, depending on the nucleophilicity of the polymerization solvent, the polymer structure contains structural units based on cyclopentadiene and/or arylpropenyl groups.     

Carbonylative cross-coupling reaction of aryl iodides with alkylaluminums by palladium complex catalysis

Secondary and/or tertiary alcohols and unsymmetrical ketones have been obtained in moderate to good yields by the palladium-catalyzed (5 mol%) carbonylative coupling of aryl iodides with alkylaluminum compounds under very mild conditions (20–50°C, 1 atm of carbon monoxide). The type of the reaction product depended on the aluminum reagent employed. While the selective formation of secondary alcohols was observed in the reaction with i-Bu₃Al, the use of Et₃Al led to a mixture of a ketone and two alcoholic products. With Et₂AlCl predominantly unsymmetrical ketones were produced. In all cases, formation of directly cross-coupled products was not observed. DME and benzene can be used as solvents, but THF is unsuitable. Nickel catalysts were found to be ineffective for this reaction.     

水相中铟促进下支链高烯丙基醇的合成

通过铟促进下醛与2-苯基-4-溴-2-丁烯在水相中经烯丙基化反应合成一系列的支链高烯丙基醇, 产率较高, 反应条件温和.     

An efficient direct alpha-alkylation of ketones with primary alcohols catalyzed by [Ir(cod)Cl]2/PPh3/KOH system without solvent

alpha-Alkylation of ketones was successfully achieved by the reaction of ketones with alcohols catalyzed by iridium complexes in the presence of a small amount of base. For example, 2-octanone was allowed to react with butanol under the influence of [Ir(cod)Cl]2/PPh3/KOH to give 6-dodecanone in good yield. The reaction was found to proceed by using a 1:1 mixture of ketone and alcohol without use of any solvent.     

Sonogashira coupling reaction of homopropargyl ether with aryl bromides and synthesis of 2,5-disubstituted 3-bromofurans

This paper presents Sonogashira coupling reaction of aryl bromides with protected homopropargyl alcohols such as tert-butyldimethyl(1-phenylbut-3-ynyloxy)silane and tert-butyldimethyl(1-(2,4-dichlorophenyl)but-3-ynyloxy)silane in piperidine catalyzed by PdCl₂/PPh₃ without copper(I). The coupling products, disubstituted acetylene, are obtained in good or excellent yields. These products can be further used for the synthesis of 2,5-disubstituted 3-bromofurans.     

Synthesis of 1,2-allenic ketones through oxidation of homopropargyl alcohols with CrO_3(cat.)/TBHP under MWI

A CrO₃ catalyzed oxidation of homopropargyl alcohols with tert-butyl hydroperoxide under microwave irradiation was found to be an efficient and rapid alternative for the preparation of 1,2-allenic ketones.The advantages of this procedure include short reaction time,less adverse impact on the environment and reasonably high efficiency.