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The reaction of oxazoles (I) with pyrazoles (II) and triazoles (V) proceeds with high regioselectivity.

Multicomponent reactions are emerging as a powerful tool in the synthesis of heterocyclic privileged medicinal scaffolds. This highlight describes a recently developed approach to the construction of the medicinally important pyrrolo[2,3-d]pyrimidine scaffold using a one-pot synthesis from commercially available starting materials via novel multicomponent reactions.

Two protocols for oxygenation of aromatic C–H bonds ortho-positioned to the phthalazine ring were developed. The transannulation of the phthalazine ring to a naphthalene moiety by an Inverse Electron Demand Diels–Alder (IEDDA) reaction led to the synthesis of naphtho[2,1-c]chromenes, 1-(ortho-hydroxyaryl)naphthalenes and 6,7-dihydrobenzo[b]naphtho[1,2-d]oxepine. This new strategy based on the utilization of transformable nitrogen heterocycles in C–H functionalization chemistry can be potentially applicable to the synthesis of a broad range of biaryl compounds.

3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone.

Multicomponent reactions are emerging as a powerful tool in alkaloid-based drug discovery. This Highlight describes several recent (all published in 2011) examples of the employment of multicomponent reactions for the synthesis of biologically active alkaloids and their medicinally relevant analogues.

A variety of fluorinated isocoumarins and dihydroisocoumarins, e.g. (III), (V), and thioisocoumarins like (VI) are prepared via construction of the isocoumarin skeleton, alkaline hydrolysis, reduction of the resulting keto acids, and cyclodehydration of the hydroxy acids formed to provide the dihydroisocoumarins (V).

Three component reaction of salicyclic aldehydes, acetyl acetic esters, and heterocyclic amines allows the synthesis of the title compounds (IV) and related compounds.

Substrates (I) undergo metal-catalyzed decomposition to yield aryl iodides which react with alkenes to give the corresponding arylated alkenes.

Base-mediated coupling of sulfonamides of type (I) and (V) with aldehydes and activated cyanides allows new access to tetra- and pentasubstituted 2-aminopyrroles.

We report on the novel properties of nitrones including their transformations via reactions with sodium malonates to give functionalized stereodefined derivatives of tertiary 3-aminoindoles or anilines, as well as fully-substituted dihydropyrroles. The outcome of the reactions is dependent mainly upon the nature of the starting C-nitrone substituent and solvent used. The formation of a new carbon–nitrogen bond in the obtained amines occurs via a nucleophilic 1,2-aryl/3-indolyl shift from C to the adjacent nitrogen.

1,2-Disubstituted pyrroles 1 were synthesized from available thioamides 4. Thioamides were initially treated with either alkylating agents or Lewis acids to give salts 5 or complexes 12 which were subsequently reacted with base to yield pyrroles 1.

A convenient synthesis of differentially protected L-chiro-inositol 7 from 2,3,4-tri-O-benzyl-D-xylopyranose is described. The structure of 7 was confirmed by its transformation to the pentabenzylated derivative of (−)-quebrachitol.

A convenient synthesis of enantiomerically pure and differentially protected L-chiro -a ndmyo-inositols as well as conduritols B and F from 2,3,4-tri-O-benzyl-D-xylopyranose via ring-closing metathesis is reported. The facile synthesis of conduritol B constitutes a short formal synthesis of ()-cyclophellitol. © 1999 Elsevier Science Ltd. All rights reserved.

A highly efficient Lewis acid-catalyzed method for the Nenitzescu synthesis of 5-hydroxyindoles with a range of substituents at N-1 and C-3 and symmetric 5,5′-dihydroxydiindoles has been developed. The amount of the catalyst (10–100 mol %) required depended on the nature of the enaminone component. It has been shown that Lewis acid plays a role in enaminone component activation through an enamine-ZnC12 complex followed by its deprotonation.

Ornamental flower growers know that placing a cut daffodil (a.k.a. narcissus) in a vase with other flowers has a negative effect on the quality of those flowers and significantly shortens their vase life. Furthermore, a common horticultural practice for the cultivation of narcissus flowers involves the introduction of cuts on the bulbs before immersing them into water. The mucilage that leaches out from the cuts is constantly removed by frequent changing of water and this leads to sprouting. These observations raise speculation that specific components in the mucilage of the narcissus bulbs may have powerful growth-inhibitory effects. Historical use of narcissus flowers, as well as at least thirty other plants of the Amaryllidaceae family, in folk medicine for the management of cancer1 speaks volumes to validate this conjecture. Indeed, powerful anticancer properties of Narcissus poeticus L. were already known to the Father of Medicine, Hippokrates of Kos (ca. B.C. 460–370), who recommended a pessary prepared from narcissus oil for the treatment of uterine tumors.2 His successors, the ancient Greek physicians Pedanius Dioscorides (ca. A.D. 40–90) and Soranus of Ephesus (A.D. 98–138) continued using this therapy in the first and second centuries A.D.3,4 In addition, the topical anticancer uses of extracts from this plant5,6 as well as from N. pseudonarcissus7–9 were recorded in the first century A.D. by the Roman natural philosopher Gaius Plinius Secundus, (A.D. 23–79), better known as Pliny the Elder.10 Even the Bible provides multiple references to the Mediterranean N. tazetta L., which has a long history of use against cancer.11 The applications of narcissus oil in cancer management continued in the middle ages in Chinese, North African, Central American and Arabian medicine.1,12 The uses of other genera of the Amaryllidaceae family were also common, e. g. Hymenocallis caribaea (L. emend Gawler) Herbert, utilized by early European medical practitioners for inflammatory tumors.13 More recently, the plants of the Amaryllidaceae have been under intense scrutiny for the presence of the specific metabolites responsible for the medicinal properties associated with this plant family. The study began in 1877 with the isolation of alkaloid lycorine from Narcissus pseudonarcissus14 and since then more than 100 alkaloids, exhibiting diverse biological activities, have been isolated from the Amaryllidaceae plants. Based on the present scientific evidence, it is likely that isocarbostyril constituents of the Amaryllidaceae, such as narciclasine, pancratistatin and their congeners, are the most important metabolites responsible for the therapeutic benefits of these plants in the folk medical treatment of cancer. Notably, N. poeticus L. used by the ancient Greek physicians, as was eluded before, is now known to contain some 0.12 g of narciclasine per kg of fresh bulbs.15 Continuing along this intriguing path, the focus of the present review is a comprehensive literature survey and discussion of the chemistry and biology of these compounds as specifically relevant to their potential use in medicine. The examination of the synthetic organic chemistry, more specifically the total synthesis efforts inspired by the challenging chemical structures of narciclasine, pancratistatin and their congeners, will be reduced to a minimum in view of the two very recent excellent reviews published on this subject.16,17

Diversely substituted 2-pyrrolines have been prepared by a novel multicomponent process involving a reaction of various N-(aryl- and alkylsulfonamido)-acetophenones with aldehydes and malononitrile. While the reaction is highly regioselective, it is not stereoselective, generating a mixture of cis and trans 2-pyrrolines. A number of analogs from both cis and trans 2-pyrroline libraries were found to have antiproliferative activity in human cancer cell lines.

A novel method for Lewis acid catalyzed Nenitzescu indole syntheses of 5-hydroxyindoles bearing different substituents in positions 1 )Alk, Bn, Ar), 2 )Me, Et, Ph), and 3 )COOEt, COMe, CONHPh) as well as tricyclic derivatives are reported. The method is simple, rapid, efficient, and allows preparation of hydroxyindoles from 1,4-benzoquinone and enamines in good to excellent yields with the use of low-polar solvents in the presence of weak Lewis acids catalysts. The formation of 5-hydroxyindoles under such mild conditions is explained in terms of a non-redox mechanism.

Current models used to predict the stereochemical outcome of organocopper conjugate addition processes focus on the nucleophilic addition step as stereochemistry-determining. Recent kinetic, NMR, kinetic isotope effect, and theoretical density functional studies strongly support the proposal that stereochemical preferences in these processes are dictated by the reductive elimination step, transforming Cu(III) to Cu(I) intermediates. A new model that considers various steric and stereoelectronic factors involved in the transition state of the reductive elimination step is proposed and then used to interpret the results of systematic studies of arylcuprate conjugate addition reactions with cis and trans gamma-alkoxy-alpha,beta-enoates. The results give rise to the following selectivity guidelines for this process. To achieve high anti-addition diastereoselectivities the use of trans esters with a bulky nonalkoxy substituent at the gamma-position is recommended. While stereoelectronics disfavor syn-addition, a judicious choice of properly sized gamma-substituents may lead to the predominant formation of syn-products, especially with cis enoates. However, high syn-selectivities may be achieved by using gamma-amino-alpha,beta-enoates.

Heterometallic clusters containing lanthanides and the group 12 metals can be isolated as crystalline compounds in high yields. These products [(py)8Ln4M2Se6(SePh)4 (Ln = Er, Yb, Lu; M = Cd, Hg)] adopt a double cubane structure with the covalent M occupying an opposing pair of external metal sites. Both Er/M compounds are strongly emissive materials, with emission lifetimes of 1.41 ms (Er/Cd) and 0.71 ms (Er/Hg) and with the Er/Cd radiative quantum efficiency twice that of the Er/Hg compound. Thermal decomposition of the Er/Cd and Yb/Cd compounds at 650 degrees C give the ternary solid-state materials CdLn2Se4.