Stereocontrolled addition of boron enolates to trans α,β-aziridine aldehydes. A new route to anti-1,2-amino alcohols

A study of the addition of boron enolates of methyl ketones to trans α,β-aziridine aldehydes is reported. The reaction proceeds with excellent anti stereoselectivity furnishing functionalized products, capable of other controlled transformations, some of which are described.     

A chiral ketone for enantioselective recognition of 1,2-amino alcohols

A novel auxillary chiral ketone has been designed, synthesized, and used to enantioselectively recognize 1,2-amino alcohols. This work proves that the keto group can serve as a chiral recognition center by imine formation supported by resonance assisted hydrogen bonding (RAHB).     

Diastereoselective synthesis of unsaturated 1,2-amino alcohols from α-hydroxy allyl ethers using chlorosulfonyl isocyanate

Diastereoselective synthesis of 1,2-amino alcohols was achieved from a highly diastereoselective allylic amination reaction of α-hydroxy allyl ethers using chlorosulfonyl isocyanate. Diastereoselectivities varied depending on the stereochemistry of the ethers used and the stability of the carbocation intermediate obtained during the reaction. We propose that this CSI reaction is the results of either a S_Ni or S_N1 mechanism, according to the stability of the carbocation intermediate.     

Synthesis of enantiopure 1-substituted, 1,2-disubstituted, and 1,4,5-trisubstituted imidazoles from 1,2-amino alcohols

A highly versatile method for the preparation of enantiopure 1-substituted, 1,2-disubstituted, and 1,4,5-trisubstituted imidazoles was developed by using the cyclocondensation reaction of a 1,2-dicarbonyl compound, an aldehyde, a 1,2-amino alcohol, and ammonium acetate.     

可见光催化醛、酮或亚胺与缺电子芳烃还原偶联构筑芳基取代醇和胺（英文）

通过C=X(X=O,N)双键极性翻转构筑碳-碳键是有机化学反应的重要合成策略.传统C=X(X=O,N)双键的极性翻转往往需要苛刻的反应条件和对水或空气敏感的强还原剂辅助,导致其适用范围受限.近年来,可见光催化反应以其独特高效的单电子转移特性,在室温条件下实现了这一类贫电子官能团向亲核性中间体的高效转化.该策略已经拓展C=X(X=O,N)双键自身或与烷基链的偶联,从而得到烷基取代的醇和胺类化合物.本文利用可见光催化反应使C=X(X=O,N)双键极性翻转与芳香化合物的直接偶联,高效温和地合成芳基取代的醇和胺.反应无需强还原剂,底物适用范围广.该方法是对可见光催化C=X(X=O,N)双键极性翻转的重要补充,具有潜在的应用价值.本文以苯甲醛和1,4-二氰基苯为底物,fac-Ir(ppy)_3为光敏剂,二异丙基乙胺为终端还原剂,DMSO为溶剂,蓝光照射12 h能够以82%的收率实现模板反应.其它光敏剂如[Ru(bpy)3]Cl_2则不能催化该反应.溶剂效应指出,丙酮、乙腈可以得到低于40%的收率,甲醇、二氯甲烷、DMF等溶剂不适用该反应体系.控制实验证实,光敏剂、二异丙基乙胺和光照三个反应组分缺一不可.底物拓展发现,不同取代基的芳基腈类化合物包括烷基取代、砜基和酯基取代甚至杂芳环取代都能很好地适用于该体系,芳基醛、酮以及亚胺作为反应的另一组分亦能高效参与该还原偶联反应.自由基捕获实验证实反应过程中涉及自由基历程.光谱淬灭实验表明,芳香腈是唯一有效淬灭激发态fac-Ir(ppy)_3发光的物种.进一步结合底物的氧化还原电位,证实芳香腈能被激发态的光敏剂fac-Ir(ppy)_3还原,但二异丙基乙胺和芳香醛、酮不能与激发态光敏剂发生作用,催化反应经历光敏剂的氧化淬灭路径.首先,光敏剂受光激发到达激发态,与芳基腈发生单电子转移.随后,二异丙基乙胺促使失去电子的铱配合物还原再生,得到相应氮自由基阳离子.该氮自由基阳离子活化反应体系中的C=X(X=O,N)双键,使其从激发态铱物种得到电子形成苄位自由基,进而与得到电子的芳基氰偶联得到最终产物.     

A highly efficient and direct approach for synthesis of enantiopure beta-amino alcohols by reductive cross-coupling of chiral N-tert-butanesulfinyl imines with aldehydes

A highly efficient and practical approach for the synthesis of optically pure beta-amino alcohols by the SmI2-induced reductive cross-coupling of chiral N-tert-butanesulfinyl imines with aldehydes was developed. This method allows the preparation of a broad range of chiral beta-amino alcohols, including functionalized ones under mild conditions. It provides a straightforward access to enantiopure beta-amino alcohols that are widely applicable in asymmetric synthesis.     

A simple chiral derivatisation protocol for H NMR spectroscopic analysis of the enantiopurity of O-silyl-1,2-amino alcohols

A simple chiral derivatisation protocol for determining the enantiopurity of O-silyl-protected-1,2-amino alcohols by ¹H NMR spectroscopic analysis is described, which involves their treatment with 2-formylphenylboronic acid and enantiopure (syn)-methyl-2,3-dihydroxy-3-phenylpropionate to afford mixtures of imino-boronate esters whose diastereoisomeric ratio is an accurate reflection of the enantiopurity of the parent amino alcohol.     

The use of acetylenic aldehydes in Baylis-Hillman reactions: synthesis of versatile allyl propargyl alcohols

The utility of acetylenic aldehydes in Baylis-Hillman reactions giving allyl propargyl alcohols in moderate to good yields is reported.     

Opening of epoxides with aromatic amines promoted by indium tribromide: a mild and efficient method for the synthesis of β-amino alcohols

A mild and efficient synthesis of β-amino alcohols by aminolysis of epoxides promoted by indium tribromide is described. The methodology is regio- and chemoselective and works well with independence of the epoxide or the aromatic amine used. In addition, the reaction can be carried out in a wide variety of undried solvents under air.     

Polyethylene glycol (PEG) as an efficient recyclable medium for the synthesis of β-amino sulfides

Aziridines undergo ring opening readily with various thiols in the presence of polyethylene glycol (PEG) to afford the corresponding β-amino sulfides in high yields with good regioselectivity under mild and neutral conditions. The PEG can be recovered and reused.     

Dy(OTf)3 in ionic liquid: an efficient catalytic system for reactions of indole with aldehydes/ketones or imines

Dy(OTf)₃ immobilized in ionic liquids was found to be an efficient catalytic system for the reactions of indole with aldehydes/ketones or imines. Enhanced activity was observed. The use of ionic liquids as the reaction media allows facile separation and recycling of the catalyst.     

Unexpected reaction of 2,2-dihydropolyfluoroalkylaldehydes with ammonia and aldehydes or ketones: a novel synthetic method for 4-fluoroalkyl-1,2-dihydropyrimidine

4-Fluoroalkyl-1,2-dihydropyrimidines were synthesized in good yields by the tri-component reaction of 2,2-dihydropolyfluoroalkylaldehydes, ammonia and aldehydes, ketones or enol ethers in the presence of zinc chloride under mild conditions.     

Sulfamic acid: an efficient, cost-effective and recyclable solid acid catalyst for the three-component synthesis of α-amino nitriles

α-Amino nitriles are synthesized by the three-component coupling reaction of aldehydes, amines and trimethylsilyl cyanide using sulfamic acid as a heterogeneous solid acid catalyst, under solvent-free conditions in excellent yields. The catalyst was recovered by simple filtration and was recycled in subsequent reactions.     

Solid-supported Pd(0): an efficient heterogeneous catalyst for aerobic oxidation of benzyl alcohols into aldehydes and ketones

Solid-supported nano- and microparticles of Pd(0) (SS-Pd) were used as heterogeneous catalysts for aerobic oxidation of benzyl alcohols. Primary and secondary benzyl alcohols gave the corresponding products in good yields. In addition, the catalysts could be reused up to five runs without significant loss of activities.     

Synthesis of conjugated enynes from ketones and aldehydes by 1,2-CC insertion and 1,2-CH insertion of carbenoids as the key reactions

The addition reactions of 1-chlorovinyl p-tolyl sulfoxides, which were derived from ketones and chloromethyl p-tolyl sulfoxide, with lithium acetylides gave adducts in moderate to good yields. Treatment of the adducts with Grignard reagents resulted in the formation of conjugated enynes in good to high yields via the 1,2-carbon-carbon insertion (1,2-CC insertion) reaction of the generated magnesium carbenoid intermediates. On the other hand, the addition reactions of 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes with lithium acetylides directly gave conjugated enynes bearing a p-tolyl sulfinyl group at the 1-position through the 1,2-carbon-hydrogen insertion (1,2-CH insertion) reaction of the generated lithium carbenoid intermediates. These procedures provide a good way for the synthesis of multi-substituted conjugated enynes from ketones and aldehydes.     

Polystyrene-supported TBD as an efficient and reusable organocatalyst for cyanosilylation of aldehydes, ketones, and imines

Polystyrene-supported TBD (PS-TBD) catalyzes cyanosilylation of both aldehydes and ketones using TMSCN to give the corresponding products in high yields. Imines were also converted into the desired α-cyanoanimes under the same conditions. PS-TBD was easily recovered and reused without significant loss of catalytic activity.     

General and efficient route for the synthesis of 3,4-disubstituted coumarins via Pd-catalyzed site-selective cross-coupling reactions

Palladium-catalyzed site-selective cross-coupling reactions of 3-bromo-4-trifloxycoumarin or 3-bromo-4-tosyloxycoumarin provide an efficient and facile route for the synthesis of 3,4-disubstituted coumarins, which include 3,4-diarylcoumarins, 3-amino-4-arylcoumarins, and 3-aryl-4-aminocoumarins. The order of reactivity of the (pseudo)halide substituents in the coumarins was found to be 4-OTf > 3-Br > 4-OTs.     

Graphite oxide: an efficient reagent for oxidation of alcohols under sonication

Graphite oxide (GO) was used as an effective oxidizing agent for the synthesis of aldehydes and ketones from various alcohols under ultrasonic irradiation. Under optimized conditions, quantitative yields of the products were obtained. Compared to other reagents used for the same chemical transformation, GO displays several advantages, including low cost, ease of synthesis, and high stability to ambient conditions.     

One-pot four-component synthesis of tetrahydrofuran derivatives involving an alkyne, an ethylene and two aldehydes via CuCl-mediated reactions of oxazirconacyclopentenes with aldehydes

In the presence of 1 equiv. of CuCl, the reaction of zirconacyclopentenes with 2 equiv. of aldehydes from −78°C to room temperature afforded tetrahydrofuran derivatives in good isolated yields upon hydrolysis with aqueous 3N HCl; oxazirconacycloheptenes, generated in situ from zirconacyclopentenes with one aldehyde, was found to be the reactive intermediate.     

An efficient and reusable vanadium based catalytic system for room temperature oxidation of alcohols to aldehydes and ketones

A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates.