Intermolecular Hetero Diels-Alder Reactions Research Articles

Accelerated Dimerization of α,β-Unsaturated D-Xylo-Hexofurano-5-ulose Derivatives through Asynchronous Hetero-Diels-Alder Reaction.

While some hetero-Diels-Alder (HDA) reactions are accelerated by either carbonyl or phosphate groups attached directly to the heterodiene moiety, the alkyl or aryl groups, on the other hand, have minimal influence. However, in this article, we demonstrate that aryl groups have a significant effect on the spontaneous dimerization reaction of α,β-unsaturated D-xylo-hexofurano-5-ulose derivatives to their respective pyrano adducts via intermolecular HDA reaction. Experimental and computational studies provide strong evidence that dimerization follows the Woodward-Katz two-stage mechanism reaction (asynchronous process), from which the aryl/aryl π-stacking interaction is mainly responsible for the rate-determining step (RDS) and electrostatic interaction for the second bond formation. Since the latter interaction is highly affected by dipolar moment, 5-ulose derivative having a strong electron-withdrawing group (R = CN; μ = 14.3 D) is spontaneously dimerized more than 15 times faster than 5-ulose that possesses an electron-donating group (R = OMe; μ = 2.1 D).

Enzymatic Intermolecular Hetero-Diels-Alder Reaction in the Biosynthesis of Tropolonic Sesquiterpenes.

Diels-Alder reactions are among the most powerful synthetic transformations to construct complex natural products. Despite that increasing of enzymatic intramolecular Diels-Alder reactions have been discovered, natural intermolecular Diels-Alderases are rarely described. Here, we report an intermolecular hetero-Diels-Alder reaction in the biosynthesis of tropolonic sesquiterpenes and functionally characterize EupfF as the first fungal intermolecular hetero-Diels-Alderase. We demonstrate that EupfF catalyzed the dehydration of a hydroxymethyl-containing tropolone (5) to generate a reactive tropolone o-quinone methide (6) and might further stereoselectively control the subsequent intermolecular hetero-Diels-Alder reaction with (1E,4E,8Z)-humulenol (8) to produce enantiomerically pure neosetophomone B (1). Our results reveal the biosynthetic pathway of 1 and expand the repertoire of activities of Diels-Alder cyclases.

Biomimetic Synthesis of Hyperjapones F-I

Hyperjapones F–I are tetracyclic meroterpenoids recently isolated from Hypericum japonicum. All four of these natural products have been synthesised using oxidative, intermolecular hetero-Diels–Alder reactions to couple their common biosynthetic precursor, norflavesone, to the appropriate monoterpene building blocks: sabinene, β-pinene, and α-pinene. The synthesis of enantiomerically pure hyperjapones H and I and comparison of their optical rotations to those of the natural samples indicated that these meroterpenoids are probably biosynthesised as either racemic or scalemic mixtures.

A highly efficient, rapid one-pot synthesis of some new heteroaryl pyrano[2,3-c]pyrazoles in ionic liquid under microwave-irradiation

A highly efficient, rapid one-pot procedure has been developed for a three-component domino intermolecular Knoevenagel–intermolecular hetero-Diels–Alder reaction, to afforded indolyl- and quinolylpyrano[2,3-c]pyrazoles from corresponding heteroarylaldehyde, pyrazolone and enol ether in ionic liquid triethylammonium acetate (TEAA) under microwave (MW) irradiation. The reaction advantageously precedes in highly regio- and stereoselective manners in combination with the ease of recovering ionic liquid used in the reaction. According to literature, the heterocycles are expected to display antitubercular activity. 2D NMR NOESY (nuclear overhauser effect spectroscopy) experiments confirm the cis-orientation of the two pyran ring hydrogens; one attached to the anomeric carbon and the second to which a heteroaryl attached.

ChemInform Abstract: Inactivated Terpenes as 2π Components in Intermolecular Hetero Diels-Alder Reactions. A Short Stereocontrolled Approach to the Robustadial and Euglobal Skeleton.

ChemInform Abstract: Inactivated Terpenes as 2π Components in Intermolecular Hetero Diels-Alder Reactions. A Short Stereocontrolled Approach to the Robustadial and Euglobal Skeleton.

An Approach to Cyclic α-Amino Acids by a Novel Hetero Diels-Alder/Intramolecular Hydantoin Enolate Alkylation Strategy: An Approach to Halichlorine

An efficient, novel synthetic strategy has been developed for preparation of cyclic α-amino acid employing an intermolecular hetero Diels-Alder reaction and an intramolecular hydantoin enolate alkylation as key steps. Application of the present hetero Diels-Alder/intramolecular hydantoin alkylation methodology to synthesis of halichlorine was explored.

Synthesis and antitubercular activity of tricyclic analogs of puupehenone

Tricyclic analogs 2a and 8 were prepared by four-step routes. The key step was an intermolecular hetero Diels–Alder reaction involving a quinone methide.

Montmorillonite-mediated hetero-Diels–Alder reaction of alkenes and o-quinomethanes generated in situ by dehydration of o-hydroxybenzyl alcohols

The intermolecular hetero-Diels–Alder reaction of in situ-generated o-quinomethanes and unactivated alkenes has been accomplished through a wet montmorillonite catalyst in a LiClO4–MeNO2 solution to give good yields of varied chromane skeletons.

Synthesis of Tetrahydro- and Dihydropyridines by Hetero Diels-Alder Reactions of Enantiopure α,β-Unsaturated Sulfinimines

Intermolecular hetero Diels-Alder reactions of the enantiopure sulfinimine 11 with the enol ethers 12-16 at 20 °C and 11 kbar lead to the tetrahydropyridines 18-22 in high yield, with very good to good endo/exo selectivities, and with an induced diastereoselectivity of up to 2.1:1. The sulfinyl group in the adducts can be removed with MeLi followed by treatment with acetyl chloride or dimethyl sulfate. According to this procedure, 21 gives either N-acetyltetrahydropyridine 29 or the N-methyldihydropyridine 32. The intramolecular Diels-Alder reaction of 26 yields 27, which is transformed into 33 and 34, respectively.

ChemInform Abstract: Solvent Effects on the Kinetics and Diastereoselectivity of the Intermolecular Hetero Diels—Alder Reaction of an Enamino Ketone with Isopropenyl Methyl Ether under High Pressure.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Scandium(III) Perfluorooctanesulfonate [Sc(OPf)3] : A Novel Catalyst for the Hetero Diels–Alder Reaction of Aldehydes with Non-Activated Dienes

Abstract Scandium(III) perfluorooctanesulfonate [scandium(III) perflate, Sc(OPf)3] was prepared from either scandium(III) chloride or oxide and perfluorooctanesulfonic acid. The perflate thus obtained acts as a novel Lewis acid catalyst for the intermolecular hetero Diels–Alder reaction of aldehydes with non-activated dienes under mild conditions. The characteristic features of the catalyst include (i) low hygroscopicity, (ii) ease of handling, and (iii) robustness for the recycling use.

Tandem Conjugate Carbon Addition–Intermolecular Hetero Diels–Alder Reactions using Ethyl 1H-Perimidine-2-acetate as a Ketene Aminal with Heating or Microwave Activation†

The reaction of ethyl 1H-perimidine-2-acetate 3 as a heterocyclic ketene-aminal with 2.1 equiv. of ethyl propiolate 4a or but-3-yn-2-one 4b affords new fused perimidines in good yields by a tandem C-addition/hetero Diels–Alder reaction; the new 1-azabuta-1,3-diene intermediates are generated in situ from the initial trans C-addition products by thermal 1,5-prototropy.

ChemInform Abstract: Molecular Switches: Calculations on the Stereodivergent Hetero Diels‐ Alder Reaction of Chiral 1‐Oxa‐1,3‐butadienes with Different Lewis Acids.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Amino Acid-Derived Chiral Acyl Nitroso Compounds: Diastereoselectivity in Intermolecular Hetero Diels-Alder Reactions

The diastereoselectivities of chiral acyl nitroso dienophiles derived from optically pure N-protected α-amino hydroxamic acids have been de- termined in intermolecular hetero Diels-Alder reactions. The cycloaddi- tion reactions afforded synthetically useful quantities of functionally rich, optically pure cycloadducts, useful for the preparation of a vari- ety of compounds of potential biological interest. Molybdenum hexacar- bonyl reduction of the cycloadducts gave optically pure allylic alco- hols. Osmium tetraoxide-catalyzed dihydroxylation of several bis-ally- lically substituted intermediates gave only the diastereomerically pure diols corresponding to naturally occurring 2',3'-dihydroxynucleoside analogs

Inter- and Intramolecular Hetero-Diels-Alder Reactions, Part 48.1 De-NovoSynthesis of Enantiopure Carbohydrates: Preparation of Ethyl β-D- and β-L-Mannopyranosides by an Asymmetrically Induced Hetero Diels-Alder Reaction

The synthesis of dihydropyrans 4 and 5 based on the asymmetrically 1,6-induced intermolecular hetero Diels-Alder reaction of the heterodiene 2 [(4S)-4-tert-Butyl-3-[(E)-4′-benzyloxy-2′-oxo-3′-butenoyl]-oxazolidin-2-one] with (Z)-1-acetoxy-2-ethoxyethene 3 in the presence of a Lewis acid is described. A reversal of facial differentiation could be achieved by variation of the Lewis acid. Thus cycloaddition of 2 and 3 preferentially yields 4 in the presence of Me2AICl and 5 using TMS-OTf. Simple transformations of 4 and 5, respectively afforded the desired ethyl mannopyranosides 12 and ent-12 diastereoselectively and in good yield.

Unactivated terpenes as 2π components in intermolecular hetero diels-alder reactions. A short stereocontrolled approach to the robustadial and euglobal skeleton.

A convergent route to the polyketide sesquiterpene skeleton of robustadial and euglobal is described.

ChemInform Abstract: Inter‐ and Intramolecular Hetero Diels‐Alder Reactions. Part 36. Diastereoselectivity and Kinetics of Intermolecular Hetero Diels‐Alder Reactions Under High Pressure. A Significant Pressure‐Induced Increase in Stereoselectivity

ChemInformVolume 20, Issue 36 Preparative Organic Chemistry ChemInform Abstract: Inter- and Intramolecular Hetero Diels-Alder Reactions. Part 36. Diastereoselectivity and Kinetics of Intermolecular Hetero Diels-Alder Reactions Under High Pressure. A Significant Pressure-Induced Increase in Stereoselectivity M. BUBACK, M. BUBACK Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorW. TOST, W. TOST Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorT. + HUEBSCH, T. + HUEBSCH Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorE. VOSS, E. VOSS Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorL. F. TIETZE, L. F. TIETZE Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this author M. BUBACK, M. BUBACK Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorW. TOST, W. TOST Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorT. + HUEBSCH, T. + HUEBSCH Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorE. VOSS, E. VOSS Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this authorL. F. TIETZE, L. F. TIETZE Inst. Phys. Chem., Univ. Goettingen, D-3400 GoettingenSearch for more papers by this author First published: September 5, 1989 https://doi.org/10.1002/chin.198936084Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume20, Issue36September 5, 1989 RelatedInformation