Synthesis and Diels–Alder cycloaddition reaction of norbornadiene and benzonorbornadiene dimers

• Bilal Nişancı,
• Erdin Dalkılıç,
• Murat Güney and
• Arif Daştan

Beilstein J. Org. Chem. 2009, 5, No. 39, doi:10.3762/bjoc.5.39

• cycloaddition reaction of dimers with TCNE and PTAD was investigated and new norbornenoid polycyclics were obtained. All compounds were characterized properly using NMR spectroscopy. Keywords: benzonorbornadiene; Diels–Alder reaction; norbornadiene; Stille coupling; Introduction Norbornadiene (1) and related

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• disconnection 3.1. Danishefsky. Mitomycin K (MMK) The retrosynthetic approach of Danishefsky is based on an intramolecular Diels–Alder reaction between a nitrosoaryl and a suitably functionalized diene (Scheme 7) [19]. Historically, this strategy was designed to synthesize the related natural product FR-900482

• introduction of the N-methyl aziridine in only three steps from an olefin by cycloaddition of methylthiophenyl azide onto the unsaturated amide 29. As mentioned before, the construction of FR-900482 was thought to occur by intramolecular hetero Diels–Alder reaction of a compound of type 32 (Scheme 8) [51

• ]. After careful analysis, it was envisioned that the reaction could occur either in the bridged mode to give the FR series (compounds 3 and 4) or in the fused mode to give access to mitomycins. Further investigations confirmed that the intramolecular hetero Diels–Alder reaction favoured the fused mode and

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• activity was investigated in benzyl ester cleavage, nitroarene reduction and a Diels–Alder reaction. The modified flavins photocatalyze the reactions, but the introduced substrate binding site does not enhance their performance. Keywords: flavin; guanidine; Kemp’s acid; photocatalysis; template

• )2, mono-Boc guanidine, CH2Cl2, rt, 20 h, 58–82%, (iii) HCl/Et2O, CH2Cl2/CHCl3, rt, 24 h, 83–90%. Oxidative photocleavage of dibenzyl phosphate. Photoreduction of 4-nitrophenyl phosphate. Photo Diels–Alder-reaction of anthracene with N-methyl-maleinimide. Oxidative photocleavage of dibenzyl phosphate

• . Results of nitrobenzene photoreduction. Results of photoinduced Diels–Alder-reaction. Supporting Information Photocatalytic experiments, UV/Vis and fluorescence spectra of 1–3, calculated gas phase conformations, 1H and 13C NMR spectra of 1, 2, 6, 7, 9, and 10. Supporting Information File 33

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• donor and an acceptor partner, such as a Diels-Alder reaction (see below). 3.3 Photodissociation Under the same experimental conditions, the photoproduct 4 was irradiated at 306 nm for 10 min until the starting material spectrum was recovered (Figure 8). Disappearance quantum yield of 4 at 306 nm was

• for MCH solution in Figure 9. One observes a drop of 50% absorbance after 8 cycles for MCH and 5 cycles for CH3CN (not shown). The photolysis at 306 nm must involve one or several photoreactions leading to products transparent at 392 nm. Thermal dissociation (a retro Diels-Alder reaction, see below

Synthesis of 2,3,6,7-tetrabromoanthracene

• Christian Schäfer,
• Friederike Herrmann and
• Jochen Mattay

Beilstein J. Org. Chem. 2008, 4, No. 41, doi:10.3762/bjoc.4.41

• and Chou presented the first synthesis of 2,3-dibromoanthracene [5], using a Diels-Alder reaction as the key step in synthesis. Twelve years later, Bowles and Anthony published an alternative synthesis for the same compound using a Bergman cyclization [6]. There are several other publications

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• Cope rearrangement and an intramolecular Diels-Alder reaction. The substrate for the Cope rearrangement was prepared by the merger of two cyclopentene units (Scheme 1). First, the addition of chloro compound 8 [18] to aldehyde 9 [19] occurred smoothly using the CrCl3/LAH system, developed by Hiyama et

• synthesis of compound 22 began with double alkylation of (+)-21 through a cuprate conjugate addition followed by treatment of the resulting enolate with methyl iodide (Scheme 5). Retro-Diels-Alder reaction of 22 in refluxing 1,2-dichlorobenzene gave α,β-unsaturated ketone 23. Trisubstituted cyclopentanone

• NaBH4) of the nitrile, MOM protection of the newly formed primary alcohol, and hydrolysis of the dioxolane gave ketone 30 and occurred as a prelude to retro-Diels-Alder reaction of the latter, leading to the α,β-unsaturated ketone 31. Compound 32 was obtained by treatment with LDA and Mander’s reagent

C₂-symmetric bisamidines: Chiral Brønsted bases catalysing the Diels- Alder reaction of anthrones

• Deniz Akalay,
• Gerd Dürner,
• Jan W. Bats and
• Michael W. Göbel

Beilstein J. Org. Chem. 2008, 4, No. 28, doi:10.3762/bjoc.4.28

• Brønsted bases in the Diels-Alder reaction of anthrones and N-substituted maleimides. High yields of cycloadducts and significant asymmetric inductions up to 76% ee are accessible. The proposed mechanism involves proton transfer between anthrone and bisamidine, association of the resulting ions and finally

• a cycloaddition step stereoselectively controlled by the chiral ion pair. Keywords: Asymmetric Catalysis; Bisamidines; Brønsted base; Diels-Alder reaction; Organocatalysis; Introduction The cycloadditions of anthrones 1 and N-substituted maleimides 2 are prominent examples of asymmetric catalysis

• °C (Table 3). Having identified suitable experimental conditions, we explored the scope of the bisamidine-catalyzed Diels-Alder reaction. The results are summarized in Table 4. Both electron-donating and electron-withdrawing substituents were tolerated and furnished products in good to excellent

Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

• Wolfgang Maison,
• Marina Büchert and
• Nina Deppermann

Beilstein J. Org. Chem. 2007, 3, No. 48, doi:10.1186/1860-5397-3-48

• following two reasons: 1. Azabicycloalkene 7 is easy to synthesize via Diels-Alder reaction.[62] 2. It was assumed to be a good substrate for RORCM because it is strained and has been shown to be susceptible to other desymmetrizing ring opening reactions in the past.[63][64] To generate appropriate

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• sequences. Recent examples of the use of silicon-containing tethers have centred upon the Diels-Alder reaction,[4][5] radical reactions[6] and olefin metathesis reactions. There have been reports of applying the temporary tethering methodology of silicon species to the P-K reaction, but with limited success

• applied as temporary tethers in reactions.[32] Silyl acetals have, for example, been applied to any reactions to which silyl ether have been applied, such as radical, Diels Alder reaction or ring closing metathesis, albeit with varying degrees of success. The advantage of silyl acetals over silyl ethers

Asymmetric aza-Diels- Alder reaction of Danishefsky's diene with imines in a chiral reaction medium

• Bruce Pégot,
• Olivier Nguyen Van Buu,
• Didier Gori and
• Giang Vo-Thanh

Beilstein J. Org. Chem. 2006, 2, No. 18, doi:10.1186/1860-5397-2-18

• Bruce Pegot Olivier Nguyen Van Buu Didier Gori Giang Vo-Thanh Laboratoire de Chimie des Procédés et Substances Naturelles, ICMMO, CNRS UMR 8182, Université Paris-Sud, 91405 Orsay Cedex, France 10.1186/1860-5397-2-18 Abstract The asymmetric aza-Diels-Alder reaction of chiral imines with

• ] ZnCl2,[5] or lanthanide triflates[6] and Brönsted acids, including HBF4 or TsOH[7] largely helped promote the reaction. Of late, catalytic asymmetric versions of the aza-Diels-Alder reaction have been explored and high stereoselectivities were reported. So far, a few catalyst systems have been quoted in

• .[29] In connection with our studies on chiral ILs and our ongoing project on asymmetric synthesis, we describe herein how chiral ILs can be used as a new chiral reaction medium in the asymmetric aza-Diels-Alder reaction between Danishefsky's diene and chiral imines. Results We have recently reported a

An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium- catalyzed multi- component domino reaction

• Dipak Prajapati and
• Mukut Gohain

Beilstein J. Org. Chem. 2006, 2, No. 11, doi:10.1186/1860-5397-2-11

• Knoevenagel/hetero-Diels-Alder reaction of 1,3-dimethyl barbituric acid with an aromatic aldehyde and ethyl vinyl ether/2,3-dihydrofuran in presence of 1 mol% of indium(III) chloride. The reaction also proceeds in aqueous media without using any catalyst, but the yield is comparatively less (65–70

• reaction of α,β-ethylenic ketones and ethyl vinyl ether or 2,3-dihydrofuran has remained unexplored.[11] Herein, we report the first example of indium(III) chloride catalysed synthesis of fused pyrimidine derivatives via a multicomponent domino Knoevenagel hetero Diels-Alder reaction. The reaction proceeds

• ], we have investigated a new, simple and efficient synthesis of novel fused pyrimidines based on inverse electron-demand Diels-Alder reaction using ethyl vinyl ether/dihydrofuran and α,β-ethylenic ketones formed in situ as heterodienes in presence of 1 mol% of indium(III) trichloride (Scheme 1). This

The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

• Ishmael B. Masesane,
• Andrei S. Batsanov,
• Judith A. K. Howard,
• Raju Mondal and
• Patrick G. Steel

Beilstein J. Org. Chem. 2006, 2, No. 9, doi:10.1186/1860-5397-2-9

• oxanorbornene adduct derived from the Diels-Alder reaction of ethyl (E)-3-nitroacrylate and furan provides a versatile template for the stereoselective synthesis of hydroxylated derivatives of 2-aminocyclohexanecarboxylic acid (ACHC). Introduction In recent years there has been a surge of interest in cyclic β

• this is that simple stereocontrolled routes to such derivatives have not been defined. In this respect, we have been exploring the use of oxanorbornene adducts derived from the Diels-Alder reaction of ethyl (E)-3-nitroacrylate and furan as versatile intermediates in the synthesis of a range of novel

• Diels-Alder reaction between furan and ethyl nitroacrylate, represented a versatile template that could be elaborated to the desired targets via a variety of complementary oxidative processes coupled with a base promoted ring fragmentation, Scheme 1. Results and Discussion Oxanorbornene Synthesis

High stereoselectivity on low temperature Diels- Alder reactions

• Luiz Carlos da Silva Filho,
• Valdemar Lacerda Júnior,
• Mauricio Gomes Constantino,
• Gil Valdo José da Silva and
• Paulo Roberto Invernize

Beilstein J. Org. Chem. 2005, 1, No. 14, doi:10.1186/1860-5397-1-14

• , Brazil 10.1186/1860-5397-1-14 Abstract We have found that some of the usually poor dienophiles (2-cycloenones) can undergo Diels-Alder reaction at -78°C with unusually high stereoselectivity in the presence of niobium pentachloride as a Lewis acid catalyst. A remarkable difference in reaction rates for

• unsubstituted and α- or β-methyl substituted 2-cycloenones was also observed. Introduction For more than 70 years, the Diels-Alder reaction, or [4+2] cycloaddition reaction, has remained as one of the best powerful organic transformations in chemical synthesis, particularly in obtaining polycyclic rings. Many

• catalyzed Diels-Alder reactions [15]. Cycloenones usually do not react with cyclopentadiene in absence of a Lewis acid. In our previous exploratory experiments we have demonstrated that niobium pentachloride promotes Diels-Alder reaction, in ethyl acetate solution, between 2-cyclohexenone (2) and