First thia-Diels–Alder reactions of thiochalcones with 1,4-quinones

• Grzegorz Mlostoń,
• Katarzyna Urbaniak,
• Paweł Urbaniak,
• Anna Marko,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2018, 14, 1834–1839, doi:10.3762/bjoc.14.156

• regioselective manner [16][20]. In cycloaddition chemistry, 1,4-quinones are applied widely both as dipolarophiles and dienophiles. In the case of [3 + 2] cycloadditions, reactions can occur chemoselectively with either the C=O or the C=C unit [21][22][23]. On the other hand, reactions with diverse 1,3-dienes

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• his process. The reaction applies to phenylacetylenes and various types of aromatic alkenes, however, its scope has been extended to dienes and disubstituted styrenes by using the less Lewis acidic CuI complex (Scheme 5b) [38]. Interestingly, cis and trans β-methyl-styrenes lead to product 14 with the

• same syn:anti ratio while 1,4-addition products containing an (E)-olefin are selectively obtained from dienes. The authors have also shown that the reaction performed in the presence of a stoichiometric amount of p-TsOH gives β-trifluoromethylstyrene derivatives instead of the expected oxy

• -trifluoromethyl compound. The benzoyloxy-trifluoromethylation of dienes has also been reported with CuCN as the catalyst. The reaction, again, is selective with respect to the olefin geometry – (E)-alkenes are exclusively obtained – and the regioselectivity – products resulting from a sterically-controlled 1,4

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• (Scheme 5). Later, this dearomatization strategy was further reinvestigated by the Ishihara group using a new chiral iodine precatalyst 10 derived from a chiral 2-aminoalcohol [39]. Its application in the oxidative dearomatization of phenol 33 and the subsequent reaction of the so-obtained dienes 34 with

• iodobiarenes to synthesize a new class of I(III) and I(V) reagents 17. These were applied for the hydroxylative dearomatization of phenolic derivatives 42 followed by the successive use of the hydroxylated products as dienes in [4 + 2] cycloaddition reactions [42]. This new reagent promoted oxygen transfer in

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• acid to afford 241 in almost quantitative yield. Bicyclic endoperoxides generated from the cycloaddition of singlet oxygen to 1,3-dienes serve as excellent synthetic precursors and have led to developments in tropone chemistry [170][171][172]. Taking advantage of the endoperoxide transformation, the

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

• Zhensheng Zhao and
• Graham K. Murphy

Beilstein J. Org. Chem. 2018, 14, 796–802, doi:10.3762/bjoc.14.67

• regioselective reaction of aryl- and α-substituted phenylallenes with the hypervalent iodine (HVI) reagent 1-chloro-1,2-benziodoxol-3-one. The reaction typically results in vicinal dichlorides, except with proton-containing α-alkyl substituents, which instead give chlorinated dienes as the major product

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• depicted in Figure 2, PQS (4a) has an OH moiety that allows for its linkage to the organocatalyst proline 4b. Also, PQS has a lipophilic component that acts as a reaction solvent for hydrophobic dienes. The latter feature allows aldol reactions to take place efficiently in water. The aldol reaction between

Synthesis of a sucrose-based macrocycle with unsymmetrical monosaccharides "arms"

• Karolina Tiara,
• Mykhaylo A. Potopnyk and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2018, 14, 634–641, doi:10.3762/bjoc.14.50

• , 1487.6857; found, 1487.6971; anal. calcd for C86H100N2O19 (1465.74): C, 70.47; H, 6.88; N, 1.91; found: C, 70.62; H, 6.96; N, 1.84. Possible route to sucrose cryptands 6. Possible route to dienes of type 9. Synthesis of macrocyclic derivative 4. Unsuccessful attempts to amines 12a and 13b. Syntheses of

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

• Longcheng Hong,
• Sebastian Ahles,
• Andreas H. Heindl,
• Gastelle Tiétcha,
• Andrey Petrov,
• Zhenpin Lu,
• Christian Logemann and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

• of cyclic frameworks, especially in the synthesis of natural products [1][2]. Aza-dienes have been utilized in IEDDA reactions for the construction of nitrogen-containing heterocyclic compounds [3][4][5][6][7][8]. Among them, 1,2-diazines are less used owing to their relative low reactivity as their

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• , Winnipeg, MB R3T 2N2, Canada 10.3762/bjoc.14.39 Abstract [Bis(trifluoroacetoxy)iodo]benzene (BTI) and (diacetoxyiodo)benzene (DIB) efficiently promote the formation of acylnitroso species from hydroxamic acids in the presence of various dienes to give the corresponding hetero-Diels–Alder (HDA) adducts in

• ) reaction of N-acylnitroso species with dienes provides the facile and highly stereoselective synthesis of 1,2-oxazines, which have been widely recognized as useful synthons in the synthesis of biologically active natural products [1]. Generally, in the presence of dienes, acylnitroso species are in situ

• and Bottke’s group have demonstrated that (diacetoxyiodo)benzene (DIB) and iodosylbenzene are applicable to the ene reactions of acylnitroso species derived from hydroxamic acids [22], the iodine(III)-mediated oxidative cycloaddition reaction of hydroxamic acids with dienes is still unknown. Herein

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• poly(allyl methacrylates) with a series of functionalized thiols. Step-growth addition polymerization for the preparation of linear polymers also was achieved using dithiols and dienes for the reaction. Recently, Chung and co-workers were successful in functionalizing natural lignin by applying Yoon’s

• sulfenylated dienes by dehydration. A series of aryl thiols with different steric and electronic properties give high yields of the thiol–yne products. Noteworthy is the high E-selectivity of the resulting alkene. Dependent on the substitution pattern of the aryl thiol a ratio up to 60:1 was observed due to

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• unusual reaction steps: (i) the conversion of the dimer 3 of dipivaloylketene (2) to bisdioxines (2,6,9-trioxabicyclo[3.3.1]nona-3,7-dienes) 4, by the addition of nucleophiles, and (ii) the facile acid-catalyzed hydrolysis of 4 with concomitant transannular cyclization. Following this route a wide variety

• derivative 37 complexes Cs+ but does not form a tetraoxaadamantane derivative. Synthetic routes to 2,4,6,8-tetraoxaadamantanes. Conversion of dipivaloylketene (2) to bisdioxines (2,6,9-trioxabicyclo[3.3.1]nona-3,7-dienes) 4 and tetraoxaadamantanes 5. 2,6,9-Trioxabicyclo[3.3.1]nonadienes (bisdioxines, 9–13

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• base to give the σ-adducts. Earlier it was found that an aza analog of DNBF – 4-aza-6-nitrobenzofuroxan (1, ANBF) ranks among the most electrophilic heteroaromatics known to date [17][18]. Compound 1 gives a remarkably stable hydrate in aqueous solution and forms Diels–Alder cycloadduts 2 with dienes

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• final product increased. Cyclic olefins and dienes proved to be more problematic substrates because they raised stereoselectivity issues and afforded poor yields. As for the mechanism, the reaction followed a similar pathway as the one proposed by the same group for the trifluoromethylation of silyl

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• were several reported examples of intra- or intermolecular Wittig reactions of ylides generated from dialkyl acetylenedicarboxylate, triphenylphosphine, and some nucleophiles. Thus, Yavari and Asghari reported an interesting synthesis of highly electron-deficient 1,3-dienes in the reaction of

• the final 1,3-dienes 89 (Scheme 54) [21]. A similar type of highly electron-deficient 1,3-dienes 90 were synthesized in yields of 78–87% in an analogous reaction with ethyl 4-aryl-2,4-dioxobutanoates with the corresponding vinylphosphonium salt (Scheme 55) [68]. In a similar reaction employing ethyl 3

• vinylphosphonium salts can be used in the Diels–Alder reaction with dienes such as isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, cyclopentadiene, and 1,3-cyclohexadiene, resulting in cyclic phosphonium salts 115 in yields of 90–96% (Scheme 66) [78]. Gelmi et al. showed that vinylphosphonium bromide 8 in

Preparation and isolation of isobenzofuran

• Morten K. Peters and
• Rainer Herges

Beilstein J. Org. Chem. 2017, 13, 2659–2662, doi:10.3762/bjoc.13.263

• general interest in synthetic and physical organic chemistry because it is one of the most reactive dienes known. A number of synthetic pathways have been published which all suffer from disadvantages such as low yields and difficult purification. We present a synthetic pathway to prepare isobenzofuran in

• laboratory scale with high yields, from affordable, commercially available starting materials. Keywords: [4 + 2] cycloaddition; Diels–Alder; isobenzofuran; trapping reagent; Introduction Isobenzofurans have been described as the most reactive dienes for Diels–Alder reactions [1][2][3][4][5]. Their high

• (mp 20 °C) with a yield of 66%. The solid compound can be stored for up to 8 months at −15 °C without decomposition (polymerization). Conclusion Isobenzofuran (1) is one of the most reactive dienes in Diels–Alder reactions and other cycloadditions. For practical applications it has been generated and

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• -dienes such a buta-1,3-diene, isoprene, cyclopentadiene and anthracene. In all cases the reaction occurred at elevated temperature and afforded the expected cycloadducts in good to excellent yields [41]. The problem of the configuration of the substituents has not been discussed, but it seems likely that

• observed by 1H NMR spectroscopy [8]. Similar systems were prepared on solid phase and used as a new molecular recognition system [44]. The [4 + 2]-cycloaddition reactions of E- and Z-1b with electron-rich 1,3-dienes have been studied extensively by Sustmann and collaborators. Thus, 1-methoxybuta-1,3-diene

• isomerization to E-1b, induced by the basic nature of the Me2N group, is a likely explanation for the observed result. In extension of the study with amino-substituted electron-rich 1,3-dienes, reactions were also performed with 1,4-bis(dimethylamino)buta-1,3-diene. These required low temperature (ca. −50 °C

Superstructures with cyclodextrins: Chemistry and applications IV

• Gerhard Wenz

Beilstein J. Org. Chem. 2017, 13, 2157–2159, doi:10.3762/bjoc.13.215

• -dienes and bulky stoppers in the presence of CDs (so-called rotaxa-polymerization) was further applied for the syntheses of water-soluble polyisoprene polyrotaxanes [25]. Furthermore, ABA-type block-copolyrotaxanes could be synthesized using this polymerization technique controlled by RAFT chain transfer

Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

• José Enrique Barquera-Lozada and
• Gabriel Cuevas

Beilstein J. Org. Chem. 2017, 13, 1969–1976, doi:10.3762/bjoc.13.192

• into elemanes by heating through a Cope rearrangement. In some cases, these transformations are so favorable that it has been mentioned that the observed elemanes are only artifacts produced at the extraction [5][6][7][8]. It is known that 1,5-dienes suffer Cope rearrangements at temperatures between

Pd(OAc)₂/Ph₃P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

• Dominik Kellner,
• Maximilian Weger,
• Andrea Gini and
• Olga García Mancheño

Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175

• heterocyclic terpenes by subsequent (hetero)-Diels–Alder or [4 + 1]-cycloadditions with nitrenes is also depicted. Keywords: dimerization; heterocycles; isoprene; monoterpene; palladium catalysis; Introduction The dimerization of conjugated dienes represents a useful, highly atom economic and straightforward

• dimerization reactions of other 1,3-dienes are reported. In this regard, isoprene has recently attracted great attention as interesting branched C5-derivative for such dimerization processes. Isoprene is a broadly used, valuable chemical for the industry [16][17]. It is used for the synthesis of rubber and

• (PhI=NR) under metal catalysis [43][44][45][46]. Although the formal [4 + 1]-cycloaddition with 1,3-dienes has been already described [47], isoprene dimers have not been enrolled as substrates in such type of reaction since the presence of the additional, less hindered double bond could lead to

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

• Jessica Hilschmann,
• Gerhard Wenz and
• Gergely Kali

Beilstein J. Org. Chem. 2017, 13, 1310–1315, doi:10.3762/bjoc.13.127

• [26][27][28] including dienes [29]. This approach drastically widens the range of suitable hydrophobic polymeric axes, to all monomers being complexed in CD or hydrophilic CD derivatives. Up to now, rotaxa-polymerization was only performed via free radical reaction without control of the polymer chain

Exploring endoperoxides as a new entry for the synthesis of branched azasugars

• Svenja Domeyer,
• Mark Bjerregaard,
• Henrik Johansson and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2017, 13, 644–647, doi:10.3762/bjoc.13.63

• sufficient material of dienes 14–16 was available to proceed to the critical cycloaddition and dihydroxylation steps and thus no further optimisation was performed. The cycloaddition reaction of dienes 14–16 with singlet oxygen was performed in a modified photochemical reactor that had been fitted with a gas

• to the phthalimide-protected dienes 15,16. When the same reaction was performed with rose bengal on diene 16 a very low yield of endoperoxide 19 was obtained and most starting material was recovered (78%) even after prolonged reaction time (40 h). However, the reaction outcome was greatly improved by

• endoperoxide synthesis. TBA-Cl = tetrabutylammonium chloride, NCS = N-chlorosuccinimide. Synthesis of endoperoxides 17–19 by [4 + 2]-cycloaddition of dienes 14–16 with singlet oxygen. The photochemical reactor was modified with a gas inlet fitted with a filter at the bottom of the reactor, and the original

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• provide the biggest number of carbon atoms during the synthesis of the 1-indanone benzene ring. For instance, 1,3-dienes in the Diels–Alder reaction provide 4 carbon atoms of the six ones needed to construct the benzene ring of 1-indanone compared to dienophiles which deliver only two of them. 2.1 From

• 1,3-dienes Wolf and Xu have synthesized 7-methyl substituted 1-indanone 241 utilizing 1,3-pentadiene (238) and 2-cyclopentenone (239) as starting compounds [96]. 7-Methyl substituted 1-indanone 241 has been obtained in the Diels–Alder reaction between 1,3-pentadiene (238) and 2-cyclopentenone (239

Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes

• Ghina’a I. Abu Deiab,
• Mohammed H. Al-Huniti,
• I. F. Dempsey Hyatt,
• Emma E. Nagy,
• Kristen E. Gettys,
• Sommayah S. Sayed,
• Christine M. Joliat,
• Paige E. Daniel,
• Rupa M. Vummalaneni,
• Andrew T. Morehead Jr,
• Andrew L. Sargent and
• Mitchell P. Croatt

Beilstein J. Org. Chem. 2017, 13, 384–392, doi:10.3762/bjoc.13.41

• stable, fully conjugated tetraene. ”Skipped diene” motifs are found in various natural products and there are few methods available to prepare these dienes [42][43][44][45][46][47][48][49][50][51][52]. Skipped tetraene systems have even fewer methods for their synthesis [53][54][55], which makes the

• products, it is hypothesized that the product may be sequestering the palladium catalyst. Two cyclic dienyl acetates were also studied (Table 3, entries 5 and 6) and they yielded tetraenes 8f and 8g. The dienes of entries 5 and 6 could have formed additional isomers by coupling to the other end of the

• a diene motif with each coupling partner, but the product maintains the independent reactivity opportunities of these isolated dienes as opposed to forming the fully conjugated 1,3,5,7-tetraene. A variety of substrates were explored where each of the unique positions on the coupling partners was

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• . Rojas et al. proposed a convenient two-step pathway for the preparation of alkyl α,ω-dienes 3. These dienes are well-known precursors in ring-closing metathesis (RCM) and acyclic diene metathesis (ADMET) chemistry [32]. They first reported the quantitative α-alkylation of primary nitriles 1 [33]. In a

• rearrangement was avoided using K/Ph3CH in hexane/ether (3 R = n-C4H9, 41% yield) or K/HMPA/t-BuOH in ether (3 R = n-C4H9, 99% yield). The latter optimized conditions allow the decyanation of alkylcyano α,ω-dienes 2 in quantitative yields with no detection of olefin isomerization (Scheme 3). Radical

• decyanation in metal dissolving conditions coupled with deprotection [30]. TBDMS = tert-butyldimethylsilyl. Preparation of α,ω-dienes [18][33]. Cyclization reaction using a radical probe [18]. Synthesis of (±)-xanthorrhizol (8) [39]. Mechanism for the reduction of α-aminonitriles by hydride donors. Synthesis