Regioselective Diels-Alder Reaction Research Articles

Preparation and Regioselective Diels–Alder Reactions of Borylbenzynes: Synthesis of Functionalized Arylboronates

In situ generated unsymmetrically substituted borylbenzynes undergo the Diels—Alder reaction with furans or pyrroles to give highly functionalized arylboronic acid adducts with high or exclusive regioselectivity.

A synthetic and in silico study on the highly regioselective Diels–Alder reaction of the polyenic antifungal antibiotics natamycin and flavofungin

The tetraenic macrolide antibiotic natamycin and the pentaenic macrolide flavofungin gave monoadducts on Diels–Alder reaction with 4-phenyl-1,2,4-triazoline-3,5-dione. The regioselectivity of the reaction as well as the conformation of the products was studied using theoretical calculations.

ChemInform Abstract: The First Total Synthesis of (.+-.)-Junicedranol Based on a Novel Anionic [1,3] Rearrangement.

Abstract The racemate of junicedranol, a sesquiterpene-alcohol with a novel carbon skeleton, was prepared through a unique anionic [1,3] rearrangement of an 8-methylenebicyclo[3.2.1]oct-6-en-2-ol giving a cyclopentadiene derivative and the facial- and regioselective Diels–Alder reaction of the cyclopentadiene with a ketene equivalent leading to the junicedranol framework.

Asymmetric Syntheses of Highly Functionalized Bicyclo[2.2.2]octene Derivatives

Highly functionalized bicyclo[2.2.2]octene derivatives bearing two quaternary carbon centers were synthesized in an asymmetric fashion. The key transformations were the regioselective Diels-Alder reaction between 3,6-dimethyl-o-quinone monoacetal and 1,1-diethoxyethylene and the subsequent enzymatic resolution. The optically active bicyclo[2.2.2]octene derivatives obtained should serve as versatile chiral building blocks for highly functionalized natural products such as ryanodine.

Copper(I) Cuboctahedral Coordination Cages: Host–Guest Dependent Redox Activity

The self-assembly of coordination cages containing internal cavities with well-defined shape and size has achieved increasing prominence not only because of their aesthetic discrete structures, but also owing to their promising functionalities as metalated containers for storage, recognition, delivery, catalysis, or as molecular reactors. Recent advances have revealed that enantioselective guest binding or stabilization of coordinatively unsaturated metal complexes can be accomplished by coordination cages, and an unusual regioselective Diels–Alder reaction could be facilitated by coordination hosts. These results may further inspire chemists to design and synthesize effective self-assembled container molecules capable of activating reactivity relying on the host–guest chemistry. So far, the construction of coordination cages has mainly involved partially blocked metal ions such as Pd and Pt or “naked” metal ions of high coordination number (4 or 6). Cage structures are less common for the low-coordinationnumber Ag, Au, and Cu ions, which can afford the unique trigonal coordination mode not accessible to other metal ions. Particularly, the Cu ion is rarely used in the cage structure assembly, probably because of its redox instability at ambient atmosphere. Nevertheless, incorporation of the redox-robust Cu ion may be able to install reactive sites into the host molecules, or to activate reactivity of the substrate molecules, which is essential to an effective molecular reactor. It has been known that many Cu-containing enzymes perform a variety of critical biological functions, and their synthetic models for C H bond activation has long been an important research objective. Herein, we report the assembly of a series of Cu cuboctahedral coordination cages by using a bulky triangular ligand and different Cu slats, which show redox stability relying on counteranions and reactivity towards arene C H bond activation depending on the host– guest adaptability. The triangular tris-monodentate ligand possessing three rotatable benzimidazole (Bim) arms, 1,3,5-tris(1-benzylbenzimidazol-2-yl)benzene (L), was prepared by substitution of 1,3,5-tris(2-benzimidazolyl)benzene. As depicted in Scheme 1, reaction of L with Cu ion at room temperature readily resulted in formation of cage structure {guest [Cu4L4]·X·solvent} (guest=ClO4 , X= 3ClO4 , 1a ; guest= I , X= 3I , 2a ; guest=MeOH, X= 4CF3SO3 , 3a, and X= 4MeC6H4SO3 , 4a). For 1–2a, Cu salts were used, whereas for 3–4a the Cu ion originated from rapid in situ reduction of Cu (see below). Interestingly, the Cu complexes 3–4a can be slowly oxidized to Cu complexes within several days with concomitant hydroxylation of L to 2,4,6-tris(1-benzylbenzimidazol-2-yl)phenol (LOH) at ambient temperature, giving the dinuclear complex [Cu2(LO)2(CF3SO3)2](CF3SO3)2·solvent (3b) and the tetranuclear complex [Cu4(LO)2(H2O)2(MeC6H4SO3)4] (4b). In contrast, Cu +

Natural tanshinone-like heterocyclic-fused ortho-quinones from regioselective Diels–Alder reaction: Synthesis and cytotoxicity evaluation

A series of new natural tanshinone-like oxoheterocyclic-fused ortho-quinone derivatives were synthesized from readily available benzofuranol and N-substituted dienes via IBX oxidation–cycloaddition–aromatization procedure. The regiospecific Diels–Alder cycloaddition reactions of N-dienes were achieved efficiently with a variety of dienophiles. It is found that the amide moiety in the molecular could be preserved or eliminated by control of the aromatization conditions. Selected oxoheterocyclic-fused ortho-quinones as well as several thioheterocyclic-fused ortho-quinones we obtained before were evaluated for their cytotoxicities on different cancer cell lines and the Structure–Activity Relationship (SAR) was discussed.

ホウ素を配向基として用いるベンザインの位置選択的 Diels-Alder反応：多置換芳香族ボロン酸誘導体の新合成

ホウ素を配向基として用いるベンザインの位置選択的 Diels-Alder反応：多置換芳香族ボロン酸誘導体の新合成

Total Synthesis of (+)‐Neomarinone

The first total synthesis of (+)-neomarinone has been achieved by following a concise and convergent route using methyl (R)-lactate and (R)-3-methylcyclohexanone as chiral building blocks. Key steps of the synthesis are the stereocontrolled formation of the two quaternary stereocenters by diastereoselective 1,4-conjugate addition and enolate alkylation reactions, and the construction of the furanonaphthoquinone skeleton by regioselective Diels-Alder reaction between a 1,3-bis(trimethylsilyloxy)-1,3-diene and a bromoquinone. The synthesis proves the relative and absolute stereochemistry of natural neomarinone.

Quantitative regio-selective Diels–Alder reaction of an unsymmetrical 1,4-dithiin and anthracene through heterogeneous solid state conversion

The solid state, Diels–Alder reaction of an unsymmetrical 1,4-dithiin and anthracene produced an adduct regioselectively via a charge-transfer complex crystal prearranged to undergo a transformation among a constitutional isomeric mixture generated in the reaction solution. The heterogeneous solid state conversion allowed the reaction to proceed in almost quantitative yield.

Synthesis of Biaryl Compounds through Three‐Component Assembly: Ambidentate Effect of the tert‐Butyldimethylsilyl Group for Regioselective Diels–Alder and Hiyama Coupling Reactions

Two for the price of one: A method has been developed for the regiocontrolled synthesis of multisubstituted biaryl derivatives. This protocol involves the use of the tert-butyldimethylsilyl (TBDMS) group to direct the regioselective Diels–Alder reaction of a 3-TBDMS-benzyne with a furan derivative and a subsequent Hiyama cross-coupling reaction of the TBDMS group with aryl iodides (see scheme).

ChemInform Abstract: Synthesis of Siloxy‐α‐Lapachone Derivatives by Chemo‐ and Regioselective Diels—Alder Reactions of 3‐Methylene‐1,2,4‐naphthotriones with Silyl Enol Ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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.

Diastereo- and regioselective Diels–Alder reactions of 2-phosphaindolizines

1,3-Bis(alkoxycarbonyl)-2-phosphaindolizines undergo Diels–Alder reactions at the C P– functionality with 2,3-dimethylbutadiene and with isoprene in the presence of sulfur with complete diastereoselectivity. The reaction with isoprene occurs with 100% regioselectivity as well. 3-Ethoxycarbonyl-1-methyl-2-phosphaindolizine, however, fails to undergo Diels–Alder reaction under these conditions. Difference in the dienophilic reactivities of mono- and bis(alkoxycarbonyl) substituted 2-phosphaindolizines and the observed regioselectivity in the Diels–Alder reaction has been rationalized on the basis of DFT calculations. The relative stabilities of the transition structures have been explained on the basis of the NBO analysis.

Synthesis of Siloxy-α-Lapachone Derivatives by Chemo- and Regioselective Diels-Alder Reactions of 3-Methylene-1,2,4-naphthotriones with Silyl Enol Ethers

O-Quinone methides, generated in situ from the Knoevenagel condensation of 2-hydroxy-1,4-naphthoquinone with aliphatic and aromatic aldehydes, take part in chemoselective hetero-Diels-Alder reactions with silyl enol ethers to give a series of siloxy-containing naphtho[2,3- B]pyran-5,10-dione (α-lapachone) derivatives in moderate to high yield. These reactions regio-selectively gave α-lapachone derivatives with an acetal structure. This regioselectivity can be rationalized by considering the frontier molecular orbital interactions of the O-quinone methide with the silyl enol ether, and by taking into account the energetically more favorable pathway leading to a zwitterion-like transition state of lower energy in a Michael addition between the two reactants.

Formal Synthesis of (-)-Platensimycin

(-)-Platensimycin, isolated from a strain of Streptomyces platensis, is an antibiotic with a novel mechanism of action. The focal step of the synthesis is an enantio- and regioselective Diels-Alder reaction, promoted by a Brønsted acid assisted chiral Lewis acid (C + D). For asymmetric Diels-Alder reactions of substituted cyclopentadienes, see: J. N. Payette, H. Yamamoto J. Am. Chem. Soc. 2007, 129, 9536.

Preparation and Diels−Alder Chemistry of 4-Vinylimidazoles

Various 4-vinylimidazole derivatives have been prepared from the corresponding 4-iodoimidazoles or from urocanic acid. Several methods for the elaboration of these vinylimidazoles and their Diels-Alder reactions are reported. All of the vinylimidazoles prepared in the course of this study react with N-phenylmaleimide quite readily with mild thermal activation providing a single cycloadduct, in most cases the initial, nonaromatic adduct. With more electron rich substrates, there is a tendency for these initial cycloadducts to undergo aromatization, ene reaction, and oxidation although this can be circumvented to a large extent by the choice of reaction conditions. Limited reactions were observed with other dienophiles, providing the expected cycloadducts in most cases, although an abnormal adduct was obtained in one case with dimethyl acetylene dicarboxylate. These substrates also participate in regioselective Diels-Alder reactions with monoactivated dienophiles, but require fairly forcing conditions, thus only providing the aromatized cycloadducts in modest yields. An investigation of substituent effects at the 2-position of the imidazole moiety was undertaken, in which electron-donating and weakly electron-withdrawing substituents are tolerated. In addition, several substrates with terminally substituted vinyl moieties have been investigated.

シリル基置換ベンザインの位置選択的 Diels-Alder 反応とその応用

シリル基置換ベンザインの位置選択的 Diels-Alder 反応とその応用

Novel Synthesis of o‐Naphthothiophenequinone Derivatives via Regioselective Diels—Alder Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of 1-Methyl-3-oxo-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylic Acid Methyl Ester

A simple and efficient method for the preparation of 1-methyl-3-oxo-7-oxabicyclo[2.2.1]hept-5-en-2-carboxylic acid methyl ester (1) is described. The first step is a highly regioselective Diels-Alder reaction between 2-methylfuran and methyl-3-bromo-propiolate. A remarkably difficult ketal hydrolysis reaction was effected by treatment with HCl, a simple reagent that was shown to be more efficient, in this case, than commonly used more elaborate methods.

The First Synthesis of a Noreremophilane Isolated from the Roots of Ligularia przewalskii.

The total synthesis of a natural product noreremophilane has been achieved in just three steps from readily available starting materials. A highly stereo- and regio-selective Diels–Alder reaction was the key step in our synthesis.

Novel synthesis of o-naphthothiophenequinone derivatives via regioselective Diels–Alder reaction

A novel procedure to construct o-naphthothiophenequinones has been achieved from readily available o-benzothiophenquinones and N-dienes via Diels–Alder reaction-aromatization sequence as key steps. The absolute regioselectivity was established via Diels–Alder reaction of o-benzothiophenquinones with rich electron N-dienes.