Divergent synthesis of fused Benzo-xanthene and oxazine derivatives via Cu-catalyst

Cu-Cu₂O combination showed synergic effects in catalyzing intramolecular Ullmann coupling reaction for halo-Betti bases to afford fused benzo-xanthenes from both electron-rich and electron-deficient aromatic systems in good yield under mild reaction conditions. The sterically hindered halo-Betti bases also provided products in excellent yield. Under optimized condition, a gram scale reaction was also performed to afford the product in excellent yield. However, without ortho-halo substituted Betti-bases failed to afford fused benzo-xanthene derivatives. Exploring the reaction optimization without Cu metal, serendipitously it was produced 1,3-oxazine derivatives in excellent yield via intramolecular cross-dehydrogenative coupling (CDC) reaction. Similarly, electron-rich, electron-deficient and sterically hindered Betti-bases provided the products in good to excellent yield under mild condition.     

Tandem reaction of heterocyclic ketene aminals with diazoesters: Synthesis of pyrimidopyrrolidone derivatives

A tandem reaction of heterocyclic ketene aminals (HKAs) with diazoesters in the presence of a Cu catalyst is demonstrated for the efficient synthesis of pyrimidopyrrolidone derivatives. The reaction shows a broad substrate scope and excellent functional group tolerance. Our method provides rapid access to diverse pyrimidopyrrolidones in moderate to excellent yields under mild reaction conditions.     

A highly selective, organocatalytic route to chiral dihydro-1,2-oxazines

[reaction: see text] The organocatalyzed asymmetric synthesis of chiral dihydro-1,2-oxazines from achiral starting materials proceeds in moderate to excellent yields and excellent enantioselectivity. This sequential reaction gives the desired products in a single pot.     

二氧化钛纳米粒子催化合成Hantzsch酯和多氢喹啉衍生物(英文)

1,4-Dihydropyridine and polyhydroquinoline derivatives have been prepared efficiently in a one-pot synthesis via Hantzsch condensation using nanosized titanium dioxide as a heterogeneous catalyst.The present methodology offers several advantages such as excellent yields,short reaction times (30-120 min),environmentally benign,and mild reaction conditions.The catalyst can be readily separated from the reaction products and recovered in excellent purity for direct reuse.     

Rhodium-catalyzed asymmetric cyclodimerization of oxabenzonorbornadienes and azabenzonorbornadienes: scope and limitations

Cationic rhodium(I)-catalyzed cyclodimerization of oxabenzonorbornadienes produced naphtho[1,2-b]furan ring systems in a single step with excellent yields and excellent enantioselectivities. The effect of various Rh(I) catalysts, Ag(I) salts, solvents, and phosphine ligands on the yield and enantioselectivity of the reaction was investigated, and the scope and limitations of this reaction with various oxabicyclic alkenes were studied. Similar results were obtained with the azabenzonorbornadiene analogues, providing the corresponding cyclodimerization products in excellent yields and excellent enantioselectivities.     

Novel bifunctional chiral thiourea catalyzed highly enantioselective aza-Henry reaction

A novel bifunctional chiral thiourea organocatalyst bearing a glycosyl scaffold and a tertiary amino group was synthesized starting from readily available alpha-D-glucose. This thiourea was proven to be an effective organocatalyst for the asymmetric aza-Henry reaction between N-Boc imines and nitromethane. The corresponding adducts were obtained in good to excellent yields with excellent enantioselectivities (up to 99.8% ee). In addition, the reaction of nitroethane also proceeded smoothly with excellent enantioselectivity, albeit with low to good diastereoselectivities.     

羽毛角蛋白稳定的钯纳米颗粒催化Suzuki偶联反应

采在温和条件下羽毛角蛋白负载的Pd纳米颗粒可高效催化水中溴代芳烃与苯硼酸的偶联反应,且具有官能团的广泛适用性,生成的联苯类化合物可在反应液中沉淀出来,具有很好的产率和纯度.催化剂通过简单过滤可重复使用7次.     

γ′‐Selective Functionalization of Cyclic Enones: Construction of a Chiral Quaternary Carbon Center by [4+2] Cycloaddition/Retro‐Mannich Reaction with 3‐Substituted Maleimides

The first example of organocatalyzed γ′‐selective functionalization of cyclic enones with 3‐substituted maleimides results in the stereoselective construction quaternary carbon center is presented. The reactions provided γ′‐functionalized cyclic enones and β‐functionalized cyclopentenones in good to excellent yields with excellent diastereo‐ and enantioselectivities. DFT calculations indicated that the reaction might proceed as a [4+2] cycloaddition/retro‐Mannich reaction which could explain the unexpected product with a chiral quaternary carbon center and the excellent stereoselectivity.     

Novel isothiocyanate transposition in 2-alkyliminothiazoles: a simple solution for regiochemical problem

Novel alkyl/aryl transposition in the reaction of 2-iminothiazoles with alkyl/aryl isothiocyanates was found out, and the reaction was very easy to handle and gave good to excellent chemical yields. Moreover, transposition reaction provided a simple but excellent solution for regiochemical problems in 2-iminothiazole synthesis.     

Phenylselenenyl chloride in acetonitrile-water : A highly convenient reagent for hydroxyselenation of olefins and preparation of cyclic ethers from dienes

The reaction of phenylselenenyl chloride with olefins in aqueous acetonitrile affords β-hydroxyalkyl phenyl selenides in excellent yields, providing the most convenient method for hydroxyselenation of olefins so far reported. When the reaction was applied to conjugated dienes, monohydroxyselenated products were obtained in good to excellent yields. From non-conjugated dienes, on the other hand, cyclic ethers containing two phenylseleno groups were produced in good to excellent yields, the first step of this reaction being the hydroxyselenation of one double bond.     

Synthesis of conjugated allenes through copper-catalyzed γ-selective and stereospecific coupling between propargylic phosphates and aryl- or alkenylboronates

A Cu-catalyzed γ-selective coupling reaction between propargylic phosphates and aryl- or alkenylboronates afforded aryl- or alkenyl-conjugated allenes. The reaction showed excellent functional group compatibility in both the propargylic substrates and the boronates. The reaction of an enantioenriched propargylic phosphate proceeded with excellent chirality transfer with 1,3-anti stereochemistry to give axially chiral aryl- and alkenylallenes.     

A convenient one-pot three component synthesis of 3-aminoalkylated indoles catalyzed by 3-chlorophenylboronic acid

An efficient protocol was developed for the synthesis of 3-aminoalkylated indoles using 3-chlorophenylboronic acid as a catalyst under ambient temperature conditions. The three-component reaction of indoles, aromatic aldehydes and N-methyl aniline offered corresponding 3-aminoalkylated indoles in excellent yields. This protocol presents some remarkable features such as mild reaction conditions, simple workup procedure and excellent yields.     

Regioselective Synthesis of SCF3‐Substituted 2,4‐Diarylquinazoline Using AgSCF3 as Trifluoromethylthiolation Reagent

A facile and efficient route to 4‐aryl‐2‐[2‐(trifluoromethylthio) aryl]quinazoline derivatives through a tandem directed Rh‐catalyzed C‐H iodination and trifluoromethylthiolation is described. The reaction proceeded under mild reaction conditions, exhibited good functional group tolerance with a broad scope of substrate and excellent regioselectivity in good to excellent yields.     

A novel microwave-mediated one-pot synthesis of indolizines via a three-component reaction

[reaction: see text] The microwave-mediated three-component reaction of acyl bromide, pyridine, and acetylene is catalyzed by basic alumina to give corresponding indolizines in excellent yields in a one-pot reaction.     

Chiral bicyclic guanidine-catalyzed enantioselective reactions of anthrones

Chiral bicyclic guanidine 1 was found to be an excellent catalyst for reactions between anthrones and various dienophiles. The catalyst can tolerate a range of substituents and substitution patterns, making several anthrone derivatives suitable for this reaction. Both Diels-Alder and Michael adducts were obtained in excellent yields, high regioselectivities, and high enantioselectivities. This is the first case of a highly enantioselective base-catalyzed anthrone Diels-Alder reaction.     

An organocatalytic approach to enantiomerically enriched α-arylcyclohexenones and cyclohexanones

The presence of a p-nitrophenyl group converts acetone into an excellent and versatile nucleophile in organocatalytic processes, able to react with α,β-unsaturated aldehydes affording β-substituted α-arylcyclohexenones via a Michael reaction/aldol reaction/dehydration sequence, which occurs in good yields, ee up to 96% and complete diastereoselectivity. The resulting compounds are excellent synthons for the diastereoselective preparation of a variety of synthetically useful polysubstituted cyclohexanones and derivatives.     

Niobium (V) chloride catalyzed Knoevenagel condensation: An efficient protocol for the preparation of electrophilic alkenes

The condensation reaction has been carryout very conveniently to obtain the corresponding substituted olefins in excellent yields and showing all the products in excellent E-geometry. The reaction conditions are very mild and applicable to various aldehydes as well as active methylene compounds.     

Chiral phosphoric acid-catalyzed addition of thiols to N-acyl imines: access to chiral N,S-acetals

The first catalytic asymmetric method to prepare enantioenriched N,S-acetals using chiral BINOL phosphoric acids is reported. The reaction combines N-acyl imines with thiols to generate products in excellent yield and enantioselectivity. The addition reaction could also be achieved with an exceptional substrate to catalyst (S/C) molar ratio. Electron-rich and electron-deficient aromatic N-acyl imines, as well as a broad range of aliphatic and aromatic thiols, showed excellent reactivity.     

Synthesis of Some New Scaffolds of Amino Isoxazolidines and Their Further Functionalization into New Class of Peptides: A New Approach

Some new class of amino isoxazolidine derivatives have been synthesized from α‐amino nitrones in water with good to excellent yields. The new isoxazolidines are further functionalized into new scaffolds of peptides with good synthetic potentiality. Simple reaction methodology, greener approaches, atom efficiency, noninvolvement of catalysts, faster reaction conditions, excellent yields, and a new approach in peptide synthesis are the attractions in these syntheses.     

3-Aminothieno[2,3-b]pyridine-2-carboxylate: Effective precursor for microwave-assisted three components synthesis of new pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4(3H)-one hybrids

In this study, ethyl 3-aminothieno[2,3-b]pyridine-2-carboxylate was taken as a versatile precursor for the one-pot three-component synthesis of related fused pyrimidine hybrids. The tandem protocol involved the reaction of 3-aminothieno[2,3-b]pyridine, dimethylformamide-dimethylacetal, and amines. The reaction afforded a new series of the target pyrimidine hybrids, linked to different arene units, in good to excellent yields. The prior reaction was evaluated in different solvents under traditional heating or microwave irradiation. Moreover, the influence of reaction temperature was also examined. The optimal conditions were obtained under microwave irradiation in dioxane at 110°C for 40 to 60 min. Additionally, by repeating the previous tandem reaction using the appropriate amines at reaction times of 20 to 60 min, a new series of pyrimidine hybrids linked to alkyl, arylthiazole, and benzo[d]thiazole units has been prepared in good to excellent yields. Furthermore, the utility of bis(amines) was examined to conduct the synthesis of new bis(pyrimidine) hybrids linked to aliphatic cores, in excellent yields, using the same protocol at 30 min reaction time.