[reaction: see text] A new iron(III) halide-promoted aza-Prins cyclization between gamma,delta-unsaturated tosylamines and aldehydes provides six-membered azacycles in good to excellent yields. The process is based on the consecutive generation of gamma-unsaturated-iminium ion further nucleophilic attack by unsaturated carbon-carbon bond. Homoallyl tosylamine leads trans-2-alkyl-4-halo-1-tosylpiperidine as major isomer. In addition, alkyne homopropargyl gives...

A new Prins cyclization process that builds up one carbon−carbon bond, heteroatom-carbon and halogen-carbon (in an oxa- azacycle) relies on iron catalyst system formed from Fe(acac)3 trimethylsilyl halide. The method displays a broad substrate scope is economical, environmentally friendly, experimentally simple. This catalytic permits the construction of chloro, bromo iodo heterocycles, by suitable combination iron(III) source, corresponding halide solvent, in high yields.

Iron (III) chloride is extensively used in organic synthesis as an ideal Lewis acid since it inexpensive, efficient, stable, environmentally friendly and a convenient agent for several useful reactions such as; polymerisations, oxidations, oxidative couplings, reductions, C bond formation, Ferrier rearrangement, one-pot multicomponent condensations, Friedel-Crafts reactions, cyclisations, glycosidation, Prins-type cyclisation, deprotection of various functional groups, reagent key steps...

[reaction: see text] A new Prins-type cyclization between homopropargylic alcohol and aldehydes in the presence of FeX(3) to obtain 2-alkyl-4-halo-5,6-dihydro-2H-pyrans good yield is described. Osmium-catalyzed cis dihydroxylation provided direct access trans-2-alkyl-3-hydroxy-tetrahydro-pyran-4-ones. Anhydrous ferric halides are also shown be excellent catalysts for standard Prins using homoallylic alcohol. Isolation an intermediate acetal provides substantiation a proposed mechanism.

Iron(III) halides have proven to be excellent catalysts in the coupling of acetylenes and aldehydes. When terminal were used main products obtained 1,5-dihalo-1,4-dienes with (E,Z)-stereochemistry contaminated some cases (E)-alpha,beta-unsaturated ketones. The former carbonyl derivatives sole isolated when nonterminal aromatic alkynes used. homopropargylic alcohols used, a Prins-type cyclization occurred yielding 2-alkyl-4-halo-5,6-dihydro-2H-pyrans. In addition, anhydrous ferric are also...

Abstract A series of functionalized tetrahydropyran and dihydropyran derivatives was synthesized by means a Prins‐type cyclization between unsaturated alcohols several aldehydes. An unprecedented dimer bearing two 4‐chloro‐5,6‐dihydro‐2 H ‐pyran scaffolds obtained in high yield. panel three representative human solid tumor cells from diverse origin used to assess the cytotoxicity compounds. Overall, results show relevance chlorovinyl group biological activity, 2‐alkyl‐4‐chloro‐5,6‐dihydro‐2...

[reaction: see text] A new type of Prins cyclization using silylated secondary homopropargylic alcohols and aldehydes yielding tetra- pentasubstituted dihydropyrans is described. The presence the trimethylsilyl group in triple bond favors minimizes 2-oxonia-[3,3]-sigmatropic rearrangement as a competitive alternative pathway. Ab initio theoretical calculations species involved rearrangements support proposed mechanism. process highly stereoselective, affording cis-dihydropyran only isomer.

Abstract The nature and influence of the N ‐sulfonyl group in aza‐Prins cyclization reactivity six‐membered aza‐cycle generated has been studied. γ,δ‐unsaturated amines with a tosyl at nitrogen atom produces 2‐alkyl‐4‐halo‐1‐tosyl‐1,2,5,6‐tetrahydropyridines halovinyl function, extraordinarily stable to further derivatization detosylation conditions. To modulate such aza‐cycles, general study reaction was performed several sulfonamides. Ring formation occurs satisfactorily both ‐nosyl...

This minireview focuses on recent advances in the synthesis of seven‐membered ring oxacycles, whether saturated, unsaturated, fused or isolated. We cover a remarkable variety strategies and methods developed during past two decades, based mainly cyclizations, ring‐closing metathesis, conjugate additions, expansions. The cyclizations can be generated directly triggered through an oxocarbenium ion, carbocation iminium‐type species. Also discussed are metatheses which precursor has...

The physical factors governing the catalysis in Lewis acid-promoted carbonyl-ene reactions have been explored detail quantum chemically. It is found that binding of a acid to carbonyl group directly involved transformation greatly accelerates reaction by decreasing corresponding activation barrier up 25 kcal/mol. makes process much more asynchronous and transition state less in-plane aromatic. remarkable acceleration induced catalyst ascribed, means strain model energy decomposition analysis...

Three new compounds, 5α-lanosta-7,9(11),24-triene-3β-hydroxy-26-al (1), 5α-lanosta-7,9(11),24-triene-15α-26-dihydroxy-3-one (2), and 8α,9α-epoxy-4,4,14α-trimethyl-3,7,11,15,20-pentaoxo-5α-pregnane (3), were isolated from Ganoderma concinna along with 12 known compounds. The structures of compounds 1 2 determined on the basis MS NMR studies. structure 3 was by MS, NMR, single-crystal X-ray diffraction. Compounds 1, 2, induce apoptosis in human promyelocytic leukemia HL-60 cells, as indicated...

From the stem bark of Dracaena draco, three new compounds, namely, draconins A−C (1−3), were isolated, along with 17 known compounds. The structures compounds isolated elucidated on basis spectroscopic data interpretation. Several showed potent cytotoxic activities measured human leukemia cell line HL-60 (IC50's from 2.0 to 9.7 μM at 72 h). mechanism by which 1 and 2 display their cytostatic properties is through induction death apoptosis, as evaluated fluorescence microscopy DNA fragmentation.

This account describes our studies on the synthesis of natural products that contain cyclic ethers in their structures. An overview main methodologies is presented and several total syntheses developed by group are described. We also discuss new applications based use Prins Nicolas reactions as key steps preparation oxygenated heterocyclic compounds. 1 Introduction 1.1 Natural Sources Biogenesis 2 Carbon–Oxygen Bond-Formation Approach 2.1 Intramolecular Opening Epoxy Alcohols Related Bromo...

Prins cyclization of bis-homoallylic alcohols with aldehydes catalyzed by iron(III) salts shows excellent cis selectivity and yields to form 2,7-disubstituted oxepanes. The is able catalyze this process unactivated olefins. This was used as the key step in shortest total synthesis (+)-isolaurepan.

Three new compounds, 2,4,4'-trihydroxydihydrochalcone (1), 3-(4-hydroxybenzyl)-5,7-dimethoxychroman (2), and 7-hydroxy-3-(4-hydroxybenzyl)chromone (3), were isolated from the resin "Dragon's blood" obtained Dracaena draco along with 18 known compounds. The structures of 1, 2, 3 determined using MS NMR techniques.

An efficient alkene aza-Cope−Mannich cyclization between 2-hydroxy homoallyl tosylamine and aldehydes in the presence of iron(III) salts to obtain 3-alkyl-1-tosyl pyrrolidines good yields is described. The process based on consecutive generation a γ-unsaturated iminium ion, 2-azonia-[3,3]-sigmatropic rearrangement, further intramolecular Mannich reaction. Iron(III) are also shown be excellent catalysts for new using homopropargyl tosylamine.

Abstract The different factors that control the alkene Prins cyclization catalyzed by iron(III) salts have been explored means of a joint experimental–computational study. salt/trimethylsilyl halide system has proved to be an excellent promoter in synthesis crossed all‐ cis disubstituted tetrahydropyrans, minimizing formation products derived from side‐chain exchange. In this iron(III)‐catalyzed reaction between homoallylic alcohols and non‐activated alkenes, two mechanistic pathways can...

Inspired by marine bioactive compounds, the principle of molecular hybridization was applied combining diverse heterocyclic systems a triazole ring, to produce new and more active compounds.

The biological activity of compound 9 obtained by introducing an α-methylene-γ-butyrolactone group into 3-(4-hydroxyphenyl)propionic acid, 1, was studied for possible effects on HL-60 cells, murine splenocytes, and human peripheral mononuclear cells (PBMC). induced apoptosis in the cell line has a clear capacity to inhibit proliferation splenocytes PBMC different mitogenic agents with no apparent toxic side effects. synthesized from its structure stereochemistry were elucidated spectroscopic methods.

Sixteen methyl glucopyranosyl glucopyranoside disaccharides (methyl β-d-Glcp(p-Br-Bz)-(1→x)-β/α-d-Glcp) containing β-glycosidic linkages (1→2, 1→3, 1→4, and 1→6) were synthesized analyzed by means of CD NMR spectroscopy in three different solvents. For each these four types disaccharides, a correlation was observed between the hydroxymethyl rotational populations around C5−C6 bond residue II with substituents anomeric configuration methoxyl group I, as well solvent. Nonbonded interactions,...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCD and 1H NMR Study of the Rotational Population Dependence Hydroxymethyl Group in .beta. Glucopyranosides on Aglycon Its Absolute ConfigurationEzequiel Q. Morales, Juan I. Padron, Mar Trujillo, Jesus T. VazquezCite this: J. Org. Chem. 1995, 60, 8, 2537–2548Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April...

The relative stability of the intermediates involved in alkyne Prins cyclization and competitive 2-oxonia-[3,3]-sigmatropic rearrangement was studied. This shown to occur slowly under typical conditions when allenyl oxocarbenium ion that results from is similar or higher energy than starting alkynyl ion. formal may be disfavored by destabilizing resultant stabilizing an intermediate dihydropyranyl cation. trimethylsilyl group as a substituent at electron-withdrawing groups (CH2Cl CH2CN)...

A highly efficient, diastereoselective, iron(III)-catalyzed intramolecular hydroamination/cyclization reaction involving α-substituted amino alkenes is described. Thus, enantiopure trans-2,5-disubstituted pyrrolidines and trans-5-substituted proline derivatives were synthesized by means of a combination starting materials, easily available from l-α-amino acids, with sustainable metal catalysts such as iron(III) salts. The scope this methodology highlighted in an enantiodivergent approach to...