Synthesis of 1,2,5- and 1,2,3,5-substituted pyrroles from substituted aziridines via Ag(I)-catalyzed intramolecular cyclization

An efficient synthesis of 1,2,5- and 1,2,3,5-substituted pyrroles has been achieved from the sequential reactions including a ring-opening of 1-(aziridin-2-yl)propargylic alcohols by various nucleophiles under mild condition followed by an intramolecular cyclization using Ag(I) catalyst.     

Stereoselective intramolecular hetero Diels-Alder reactions of 1-oxa-1,3-butadienes: a novel approach for the synthesis of complex annulated uracils

The intramolecular hetero Diels-Alder reactions of 1-oxa-1,3-butadienes 4, obtained from salicylaldehyde 1 via O-allylation followed by Knoevenagel condensation with barbituric acids 3 in the presence of hydrochloric acid as catalyst, affords the tetracyclic uracil derivatives 5 and 6 in a stereoselective manner and high overall yields.     

Reactions of [LiC(SiMe2H)3]·2THF: Sterically hindered tris(dimethylsilyl)methane derivatives and their hydrosilylation

Treatment of LiC(SiMe₂H)₃]·2THF (1) with alkeny1chlorosilanes produced sterically hindered alkenylsilanes (4–10) of structure H₂C=CH---(CH₂)_nSiRR′C(SiMe₂H)₃ (R=Me; R′=Me or Cl; n=0, 1, or 4). The Peterson reaction of 1 with carbonyl compounds gave sterically hindered olefins R(R′)C=C(SiMe₂H)₂. Pt or Rh catalyzed intramolecular hydrosilylation of H₂C=CHSiMe₂C(SiMe₂H)₃ (4) occurred to produce a new 1,3-disilacyclobutane derivative 15. Intermolecular hydrosilylation was favored for 5, 8, and 10, producing oligomeric products.     

Synthesis of 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional groups via Peterson protocol

Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional and reactive groups in a convenient one-pot operation via the Peterson protocol. Then poly(styrene) and poly(α-methylstyrene) (?&II) random homopolymers were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. The aldehyde group is introduced by direct electrophilic substitution of polymers ? and II. This formylation reaction was conducted in two different solvents: dichloromethane (CH₂Cl₂) and nitrobenzene (PhNO₂). The results indicate that PhNO₂ appeared to be a more suitable solvent for such an aldehyde functionalization of the polymers. The formylated polymers (I_CHO, II_CHO) were then converted to Si-H functionalized polymers (I_Si-H, II_Si-H) via reaction with tris(dimethylsilyl)methyllithium, (HMe₂Si)₃CLi.     

An efficient synthesis of 2-(guaiazulen-1-yl)furan derivatives via intramolecular Wittig reactions

An efficient and mild synthesis of 2-(guaiazulen-1-yl)furans,starting from easily accessible 1-(3-aryl-2-cyanopropenoyl) guaiazulenes,tributylphosphine and acyl chlorides,is described.The strategy employs the intramolecular Wittig protocol as a key step to append the crticial furan ring,leading to the highly functional furans in good yields.     

Ring opening of 2-(bromomethyl)-1-sulfonylaziridines towards 1,3-heteroatom substituted 2-aminopropane derivatives

1,3-Heteroatom substituted 2-aminopropane derivatives have been prepared from 2-(bromomethyl)-1-sulfonylaziridines for the first time using sodium azide or different potassium phenoxides in water in the presence of silica gel. The applicability of 1-arenesulfonyl-2-(bromomethyl)aziridines for the synthesis of functionalized sulfonamides has also been demonstrated towards different 1,3-dialkoxy-2-(tosylamino)propanes and 1,3-dialkylthio-2-(tosylamino)propanes upon treatment with the appropriate sodium alkoxide or sodium alkylthiolate in the corresponding alcohol or in methanol, respectively.     

Synthesis of furan derivatives of cyclic β-amino acid cispentacin via intramolecular nitrile oxide cycloaddition

Two furan derivatives of cispentacin have been synthesized starting from a d-mannitol derived conjugated nitroolefin through intramolecular nitrile oxide cycloaddition (INOC) as a key step.     

Synthesis of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of N-substituted-2(3H)-benzothiazolones

The decarbalkoxylations of disubstituted geminal diesters by water–DMSO with added salts (KCN or NaCN) is a convenient preparative route leading to the corresponding monoesters. Herein, we described an efficient and very simple methodology for the preparation of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of the corresponding N-substituted-2(3H)-benzothiazolones in the presence of disubstituted geminal diester, KCN, and water–DMSO.     

A simple and efficient approach for the synthesis of a novel class aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives via intramolecular nucleophilic substitution reaction

In this study, we synthesized a new series of substituted aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives (6-24) in yields ranging from 42 to 70% with an interesting mechanism that involves internal nucleophilic substitution followed by an S_N2-type nucleophilic substitution. First, 1-(4-chlorophenyl)-2-((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethanone (3) was synthesized from the reaction of 5-methyl-1,3,4-thiadiazole-2-thiol (1) with 2-bromo-1-(4-chlorophenyl)ethanone (2) in the presence of potassium hydroxide. Then, 1-(4-chlorophenyl)-2-((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethanol (4) was synthesized by a reduction reaction of this compound using NaBH₄. Finally, 5-methyl-3-alkyl-1,3,4-thiadiazol-2(3H)-one derivatives (6-24), which are the target compounds, were synthesized from the reaction of this compound (4), which is a secondary alcohol with various alkyl halides (5a-n) in the presence of sodium hydride (NaH). This study presents an interesting reaction mechanism related to the synthesis of aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives that is not recorded in the literature.     

Ring opening reactions of 1-arenesulfonyl-2-(bromomethyl)aziridines

The reactivity of 1-arenesulfonyl-2-(bromomethyl)aziridines with respect to lithium dialkylcyanocuprates and lithium dialkylcuprates (Gilman reagents) has been evaluated for the first time, pointing to the conclusion that these substrates can be applied successfully as synthetic equivalents for the 2-aminopropane dication synthon towards 2-alkylaziridines and α-branched N-tosylamides in good yields.     

A powerful, practical and chemoselective synthesis of 2-anilinoalkanols catalyzed by Bi(TFA)3 or Bi(OTf)3 in the presence of molten TBAB

A facile and efficient synthesis of β-amino alcohols by ring opening of epoxides with anilines in good to excellent yields in the presence of catalytic amounts of Bi(TFA)₃ or Bi(OTf)₃ via the use of molten tetrabutylammonium bromide (TBAB) as an ionic liquid is described. In addition, the observed chemoselectivity can be considered as a noteworthy advantage of this method.     

Synthesis of chroman-4-one and indanone derivatives via silver catalyzed radical ring opening/coupling/cyclization cascade

A variety of chroman-4-one and indanone derivatives were conveniently synthesized from readily available cyclopropanols and alkenyl aldehydes via a silver catalyzed radical ring-opening/coupling/cyclization cascade. The reaction proceeded under mild and neutral conditions with broad substrate scope and afforded the desired products in moderate to good yields. A probable mechanism for the cascade reaction was also proposed.     

Efficient formal synthesis of (±)-axamide-1 and (±)-axisonitrile-1 via an intramolecular Hosomi-Sakurai reaction

A formal synthesis of (±)-axamide-1 and (±)-axisonitrile-1 was achieved by using an intramolecular Hosomi-Sakurai reaction of the allylsilane derivative, as a key step, in which [(3-but-3-en-1-yl-3-methylcyclohex-1-en-1-yl)methyl](trimethyl)silane was transformed to a bicyclic compound possessing a core carbon framework under the oxidative dihydroxylation reaction conditions, in one step.     

A new approach towards 2-amino-1-aryloxy-3-methoxypropanes from 1-arylmethyl-2-(bromomethyl)aziridines

1-Arylmethyl-2-(bromomethyl)azirdines were converted into the corresponding 2-(aryloxymethyl)aziridines upon treatment with the appropriate potassium phenoxides in DMF/acetone in excellent yields, followed by regioselective ring opening towards N,N-di(arylmethyl)-N-(2-bromo-3-aryloxypropyl)amines using benzyl bromide in acetonitrile. Treatment of the latter β-bromoamines with sodium methoxide afforded the desired 2-amino-1-aryloxy-3-methoxypropanes as the major compounds (49-58%) besides the isomeric 3-amino-1-aryloxy-2-methoxypropanes in minor quantities (9-15%).     

An efficient approach to isoindolo[2,1-b][2]benzazepines via intramolecular [4+2] cycloaddition of maleic anhydride to 4-α-furyl-4-N-benzylaminobut-1-enes

Acylation of 4-α-furyl-4-N-benzylaminobut-1-enes with maleic anhydride gave 4-oxo-3-aza-10-oxatricyclo[5.2.1.0^1,5]dec-8-ene-6-carboxylic acid via amide formation followed by intramolecular Diels-Alder reaction of furan (IMDAF). The cycloaddition proceeded under mild reaction conditions (25 °C) and provided only the exo-adduct in quantitative yield. Treatment of this compound with PPA gave isoindolo[2,1-b][2]benzazepine derivatives via ring opening, aromatization and intramolecular electrophilic alkylation. In order to extend the scope of the reaction sequence, 7-oxo-5,11b,12,13-tetrahydro-7H-isoindolo[2,1-b][2]benzazepine-8-carboxylic acids were further transformed into useful synthetic intermediates.     

Ring opening reaction of furan with high regio- and diastereo-selectivity via controlled addition of isatin-derived diazoamides

Reaction of cyclic diazoamides with furan systems using rhodium(II) acetate as a catalyst afforded a variety of (3Z)-3-[(2E)-4-oxopent-2-en-1-ylidene]indol-2-ones in a regio- and diastereo-selective manner. The diastereoselectivity was based on the flow rate of cyclic diazoamides. The representative products were characterized by single-crystal X-ray analyses.     

用(R)-(+)-缩水甘油的亲核开环反应制备手性连二醇

以D-甘露醇为原料合成(R)-(+)-缩水甘油1。该环氧化合物的亲核开环反应为高立体选择性地(93%-96%e.e.)制备各种手性连二醇提供了一条简便途径。     

Synthesis of quaternary allylammonium salts via ring opening of 1-benzyl-2-(bromomethyl)aziridines

Treatment of 1-benzyl-2-(bromomethyl)aziridine, and some aryl substituted analogues, with an excess of iodomethane resulted in N-allyl-N-benzyl-N,N-dimethylammonium salts, in good yields. These quaternary allylammonium salts are of importance in different fields, from organic synthesis and polymeric chemistry to agricultural use.     

Synthesis of 2-aryl-1,2,3,4-tetrahydroquinazolin-1-ols and their conversion to 7-aryl-9H-6-oxa-5,8-diaza-benzocycloheptenes

2-Aminobenzylamine was reacted with corresponding aromatic or heteroaromatic aldehydes to give 1,2,3,4-tetrahydroquinazolines 1 the oxidation of which with H₂O₂-tungstate in methanol led to the formation of the corresponding 1,2,3,4-tetrahydroquinazolin-1-ols 2. A one-pot procedure involving the treatment of the in situ formed quinazoline 1 with H₂O₂-tungstate again led to the formation of 2. Compounds 2 react with 2 equiv of aryl isocyanate in toluene at room temperature to produce compounds 3. The probable mechanism of the ring-expanding carbamoylation of quinazolin-1-ols 2 to 6-oxa-5,8-diaza-benzocycloheptenes 3 is discussed.     

利用Kirkendall效应制备Ce1-xTixO2中空纳米球

利用Kirkendall效应, 在溶剂热条件下成功制备了复合氧化物Ce_1-xTi_xO₂的纳米空心球, 并通过XRD, TEM和XPS等测试手段进行了表征. 结果表明, Ce_1-xTi_xO₂纳米空心球的粒径为65 nm, 小于初始状态的CeO₂纳米球, 并且Ce_1-xTi_xO₂纳米空心球的结构与前驱体CeO₂晶体结构相同, 均为面心立方结构. Ti/Ce摩尔比和温度是影响产物形貌和结构的重要因素, 通过实验得出最佳反应条件为n(Ti)∶n(Ce)=8∶10, 于190 ℃反应8 h.