Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• , CS 50837, 35708 Rennes Cedex 7, France Centre for Sustainable Chemical Processes, Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K. 10.3762/bjoc.10.19 Abstract In the last few years, multicomponent reactions involving boron substituted 1,3-dienes have emerged as important

• tools in synthetic organic chemistry. The most significant recent results and developments obtained in this area are reported in this review. Keywords: allylboration; boron compounds; Diels–Alder; 1,3-dienes; multicomponent reactions; Petasis borono–Mannich; Suzuki couplings; Introduction

• other amine partners [13][14][15]. Subsequently, other multicomponent reactions involving trialkylborane [16][17], alkenyl- [18][19], aryl- [20][21], allyl- [22], allenyl- [23], and alkynylboronic acids or esters [24][25][26] have been reported in the literature. Boron-substituted 1,3-dienes and

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• and coworkers used this chemistry with propargylic acetate 255 to achieve cyclopropanation with various dienes, for example cyclopentadiene, to generate a cis/trans-mixture of divinylcyclopropanes 256. Heating of this mixture of compounds resulted in the formation of bridged tricycle 257 in good yield

• wise mechanism and involves charged intermediates. Nevado and coworkers [206] applied a closely related reaction to propargylic acetate 262 using a cationic gold(I) catalyst, which was used to selectively cyclopropanate the less hindered double bond of dienes like 263. Spontaneous DVCPR provided

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• peroxides are based on three key reagents: oxygen, ozone, and hydrogen peroxide. These reagents and their derivatives are used in the main methods for the introduction of the peroxide group, such as the singlet-oxygen ene reaction with alkenes, the [4 + 2]-cycloaddition of singlet oxygen to dienes, the

• reaction products were separated by column chromatography. 1-Hydroxy-1-phenylpentan-3-one (42) was isolated as a by-product in 16% yield [248]. The peroxidation of 1,4-dienes 43a,b with the Co(modp)2/Et3SiH/O2 system according to a similar reaction scheme gave dioxolanes 44a,b. Acetophenone (45) was

• peroxides. In some cases, the reaction with 1,5-dienes 46a–d produces, along with 1,2-dioxanes 51 (desilylation products of the corresponding 1,2-dioxanes 48), 1,2-dioxolanes (52b,d) as a result of cyclization of the corresponding peroxysilyl epoxides 49. In these reactions, unsaturated triethylsilyl

One-pot cross-enyne metathesis (CEYM)–Diels–Alder reaction of gem-difluoropropargylic alkynes

• Santos Fustero,
• Paula Bello,
• Javier Miró,
• María Sánchez-Roselló,
• Günter Haufe and
• Carlos del Pozo

Beilstein J. Org. Chem. 2013, 9, 2688–2695, doi:10.3762/bjoc.9.305

• for the creation of carbon–carbon bonds has exponentially increased, due to the availability of well-defined catalysts [1][2][3]. Particularly, enyne metathesis (EYM) is a powerful synthetic tool for generating 1,3-dienes by redistributing unsaturated functionalities between an alkene and an alkyne

• probably due to its inherent problems of selectivity, which results in the formation of a mixture of E- and Z-isomers [14]. The discovery of the beneficial effect of ethylene has changed this tendency allowing the straightforward preparation of 1,3-dienes [15][16]. Thus, during the ethylene gas promoted

• very fruitful for the preparation of 1,3-dienes, this protocol has remained almost unexplored for propargyl fluorides [26]. In this context, we have recently established a tandem multicomponent protocol CEYM–Diels–Alder reaction of several difluoropropargylic derivatives [27][28] mediated by 1,7

Reaction of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithiethane with N-vinyl compounds

• Viacheslav A. Petrov and
• Will Marshall

Beilstein J. Org. Chem. 2013, 9, 2615–2619, doi:10.3762/bjoc.9.295

• hexafluorothioacetone dimer (2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithiethane (1) were shown to react with a wide variety of electron-rich olefins and dienes, producing the corresponding cycloadducts. Reported examples include the corresponding thietanes, derived from the reaction of HFTA with vinyl ethers, vinyl

• sulfides, cyclic dienes and styrenes [1][2], fluoride anion-catalyzed reactions of compound 1 with vinyl ethers [1][3][4], vinyl sulfides [3], ketene dimethylacetal [5], styrenes [6][7], cyclic dienes [8] and quadricyclane [9]. At this point, no data for the reaction of HFTA or HFTA dimer with vinylamines

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• , carboxylic acids required a higher loading of catalyst (5 mol %), but an acceptable yield was obtained even when sterically demanding 2-methylpropionic acid was employed as the nucleophile (Scheme 1b). Li and co-workers exploited the [Au(III)]-catalyzed addition of phenols and naphthols to conjugated dienes

• hydroamination of alkenes. Detailed computational studies on the addition of benzyl carbamate to dienes revealed the protodeauration as the rate-determining step of the reaction [34]. Mechanistically, the initial stage was determined dealing with the energetically favourable substitution of the TfO− ligand from

• addition of carbamates, sulfonamides and imidazolidinones to linear and cyclic dienes 17 in the presence of catalytic amounts of PPh3AuOTf (Scheme 6). The method featured excellent 1,2-regioselectivity and high chemoselectivity, providing protected allylamines 18, in good yields, using nearly equimolar

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• carboxylic acid and (iii) a Ru–lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation. Keywords: dienes; enzyme catalysis; lactones; metathesis

• one step. An example recently published by us combines RCM of butenoates 2 with a base-induced highly stereoselective ring opening of the transient metathesis products 4, furnishing exclusively Z,E-dienes 3 [24]. We assume that the reaction proceeds via formation of an enolate 5, followed by

Consecutive cross-coupling reactions of 2,2-difluoro-1-iodoethenyl tosylate with boronic acids: efficient synthesis of 1,1-diaryl-2,2-difluoroethenes

• Ju Hee Kim,
• Su Jeong Choi and
• In Howa Jeong

Beilstein J. Org. Chem. 2013, 9, 2470–2475, doi:10.3762/bjoc.9.286

• yields. Unsymmetrical di-coupled products 4 were obtained in high yields from the reactions of 3 with 2 equiv of boronic acids in the presence of catalytic amounts of Pd(OAc)2 and Na2CO3. Keywords: boronic acids; cross-coupling reaction; 1,1-diaryl-2,2-difluoroethene; 1,1-difluoro-1,3-dienes; 2,2

Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings

• Shinichiro Fuse,
• Nobutake Tanabe,
• Akio Tannna,
• Yohei Konishi and
• Takashi Takahashi

Beilstein J. Org. Chem. 2013, 9, 2336–2343, doi:10.3762/bjoc.9.268

• ligand framework influences the reactivity of the metal center. That is why sterically crowded and neutral-chelating diimine ligands have garnered a great deal of attention [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In recent years, N-aryl 1,3,5-triazapenta-1,4-dienes 1 and 2 have been

• homopolymerization nor copolymerization of ethylene with polar monomers by using the catalysts derived from N-aryl-1,3,5-triazapenta-1,4-dienes 1–3 have been reported [18][19]. Thus, we tested the polymerization activity of the catalyst 12 in the copolymerization of ethylene with 5-norbornen-2-ol (NBO) and ethyl

• . The reaction mixture was concentrated in vacuo. The residue was used for the next reaction without further purification. General procedure for micro-flow synthesis of 1,2,3,4,5-pentaaryl-1,3,5-triazapenta-1,4-dienes 3b and 3c: A T-shape mixer and reaction tube were immersed in a water bath (20 °C

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• -tuning of the catalyst and substrate is required to achieve excellent enantioselectivities. More recently, Nevado and co-workers have shown that propargyl acetates 4 react with 1,3-dienes in the presence of a gold catalyst to give good yields of cycloheptadiene products of type 5; thus the process could

• participating in concerted [4C(4π) + 3C(2π)] cycloadditions with conjugated dienes [54], a process related to the classical oxyallyl cation [4 + 3] cycloadditions [55][56][57]. An initial screening demonstrated that PtCl2 was a good catalyst for promoting these intramolecular [4C + 3C] cycloadditions [54

• cycloadditions of allenes have been scarcely studied. However, significant progress has been made in the last 4 years. While the development of an intermolecular [4 + 3] cycloaddition between allenes and dienes remains elusive, neither in a racemic nor enantioselective fashion [69], it has been shown that

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• been the subject of several theoretical investigations [7][8][9][10]. The necessary nitronic ester precursors are readily preparable by Lewis acid-promoted [4 + 2]-cycloaddition reactions of nitroalkenes with appropriate dienes, a general reaction first reported by Denmark and coworkers (Denmark Diels

• substitution patterns. We were also interested in determining the double bond specificity of the Denmark Diels–Alder reaction for unsymmetrical dienes. Previous work on cyclopentadiene and cyclohexadiene has shown that the reaction can be quite specific to give one of two possible regioisomers [11][12]. In the

• cycloadducts resulting from C–C bond formation at the end of the conjugated diene system were observed, in keeping with reported results for other conjugated dienes [1][11][12]. However, cycloaddition was relatively indiscriminant at the two double bonds of the diene in this initial experiment. The reaction

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping

• Skrollan Stockinger and
• Oliver Trapp

Beilstein J. Org. Chem. 2013, 9, 1837–1842, doi:10.3762/bjoc.9.214

• differences are samller compared to the on-column system. Surprisingly, the substituents of the anthracene derivatives show a more pronounced effect on the conversion compared to the classical synthesis in a flask, which might be explained by differences in the relative migration velocities of the dienes. We

Gold-catalyzed intermolecular coupling of sulfonylacetylene with allyl ethers: [3,3]- and [1,3]-rearrangements

• Jungho Jun,
• Hyu-Suk Yeom,
• Jun-Hyun An and
• Seunghoon Shin

Beilstein J. Org. Chem. 2013, 9, 1724–1729, doi:10.3762/bjoc.9.198

• group to give C and allyl cation, which evolves into 4 and a mixture of dienes. This was especially severe for substrates having an α-substituent (2i–l) where the stability of the resulting allyl cation further facilitates the ionization. The combination of the resulting intermediate C and the allyl

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• hindrance from bulky protecting groups, as well as susceptibility of the skipped dienes therein to double bond isomerization and migration under basic conditions. However, the ripostatins intrigued others, and three total syntheses of ripostatin B were published in succession in 2012 [6][7][8]. Tang and

• the double 1,4-diene (Figure 2). Notwithstanding the successful syntheses of ripostatins, preparation of configurationally defined skipped polyenes (1,4-dienes and higher homologues) remains a significant challenge in organic chemistry. The doubly allylic protons found in these structures may be

• sensitive to strong base as well as hydrogen abstraction [10][11]. While classical methods for the preparation of 1,4-dienes include partial reduction of alkynes and carbonyl olefination, a variety of transition-metal-mediated processes have been developed for the synthesis of skipped dienes of varied

Establishing the concept of aza-[3 + 3] annulations using enones as a key expansion of this unified strategy in alkaloid synthesis

• Aleksey I. Gerasyuto,
• Zhi-Xiong Ma,
• Grant S. Buchanan and
• Richard P. Hsung

Beilstein J. Org. Chem. 2013, 9, 1170–1178, doi:10.3762/bjoc.9.131

• handled vinylogous amides and vinyl iminium salts. It provides a significant complementary, if not superior, approach to aza-[4 + 2] cycloadditions in constructing piperidines, because the aza-dienes and imines required are not always the most accessible and/or easily handled substrates given the problems

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

• Mostafa Kiamehr,
• Firouz Matloubi Moghaddam,
• Satenik Mkrtchyan,
• Volodymyr Semeniuchenko,
• Linda Supe,
• Alexander Villinger,
• Peter Langer and
• Viktor O. Iaroshenko

Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124

• Katalyse e.V. an der Universität Rostock, Albert-Einstein-Straße 29a, D-18059 Rostock, Germany 10.3762/bjoc.9.124 Abstract The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.02,7]trideca-2(7),11-dienes. The reaction

• reaction conditions as well as bases with various combinations of time and temperature did not deliver any positive results. During the course of this work we encountered the low stability of 8-oxa-10-aza-tricyclo[7.3.1.02,7]trideca-2(7),11-dienes; decomposition was observed in polar solvents, i.e., in

• summary, we have studied the dicomponent binucleophilic cycloaddition of 1,3-diketones with diverse substituted pyridinium salts. The reaction took place under mild conditions and provided an efficient route to 8-oxa-10-aza-tricyclo[7.3.1.02,7]trideca-2(7),11-dienes with a wide range of substituents

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• dioxygenation of seco-dienes such as 20 implies that this iterative method may find usage in organic synthesis. In this mode, we can install four hydroxy groups on a seco-diene with different protecting groups. Although several research groups have investigated the desymmetrization of seco-diene by using

• synthetic targets. Conclusion In summary, with a comprehensive validation of PIFA-promoted cyclization of alkenes, a synthetically useful desymmetrization approach via the dioxygenation of alkenes was developed. The “stop-and-flow” strategy allows us to easily functionalize seco-dienes step-by-step

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

• Rajendra K. Jangid,
• Nidhi Sogani,
• Neelima Gupta,
• Raj K. Bansal,
• Moritz von Hopffgarten and
• Gernot Frenking

Beilstein J. Org. Chem. 2013, 9, 392–400, doi:10.3762/bjoc.9.40

• could be enhanced by complexing the P-atom of phosphinine to a metal carbonyl, such as W(CO)5 [15][20]. Thus, the phosphinine-η1-P-W(CO)5 complex reacted with 1,3-dienes to afford [2 + 4] cycloadducts. By following the same strategy, we recently reported our theoretical and experimental results of the

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• group; (2) alkynes bearing a directing group; (3) strained cyclopropenes; (4) unactivated alkynes or alkenes; and (5) substrates that have two carbon–carbon unsaturated bonds (allenes, dienes, enynes, or diynes). Keywords: alkene; alkyne; carbomagnesiation; carbometalation; carbozincation; transition

• bearing a directing group; (3) cyclopropenes; (4) unactivated alkynes or alkenes; and (5) substrates that have two carbon–carbon unsaturated bonds (allenes, dienes, enynes, or diynes). Review Carbomagnesiation and carbozincation of electron-deficient alkynes Since conjugate addition reactions of

• -bis(diphenylphosphino)benzene (dppbz) ligand efficiently suppressed the elimination pathway to provide the corresponding carbozincation product 4o in high yield (Scheme 45, reaction 4n to 4o) [132]. Carbomagnesiation and carbozincation of allenes, dienes, enynes, and diynes Interesting transformations

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Asymmetric Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene

• Magnus Rueping and
• Sadiya Raja

Beilstein J. Org. Chem. 2012, 8, 1819–1824, doi:10.3762/bjoc.8.208

• -dienophiles has been investigated and it was shown that the reaction between arylimines and dienes, catalyzed by chiral Brønsted acids, proceeds with high levels of enantioselectivity. However, these reactions are limited to electron-rich dienes including Brassard’s and Danishefsky dienes [24][25][26][27][28

• ][29][30][31][32]. To the best of our knowledge the enantioselective Brønsted acid catalyzed aza-Diels–Alder reaction of imines with less-electron-rich dienes has not been reported. Thus, we decided to examine the unprecedented Brønsted acid catalyzed aza-Diels–Alder reaction of cyclic C-acylimines

• applied. In all cases the corresponding tetracyclic products were obtained in high yields and with excellent diastereo- and enantioselectivities. However, the use of less reactive dienes including cyclohexadiene or linear 1,3-pentadienes resulted in reduced product formation or provided the desired

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• efficient way of making 6-membered rings, particularly in the case of electronically similar dienes and dienophiles, which can require high temperatures and long reaction times for the thermal cycloaddition to occur [28]. Many different transition-metal catalysts have been described for these types of

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

• Stefan Bräse,
• Nicole Volz,
• Franziska Gläser and
• Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

• enantioselective organocatalytic Diels–Alder reaction was reported by MacMillan in his pioneering work in 2000 [17]. The activated iminium ion, formed through condensation of imidazolidinone and an α,β-unsaturated aldehyde, underwent reactions with various dienes to yield [4 + 2]-cycloadducts in excellent yields

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• number of examples [70][71]. Hoornaert and co-workers have also employed pyrazinones as dienes in IEDDA reactions to prepare α-carbolines [72]. Though the existing synthetic routes can readily produce various α-carbolines, the intramolecular IEDDA approach outlined in Scheme 1 has several advantages from

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• and Heck reactions, respectively [21]. The dienes obtained during these transformations were successfully converted in Diels–Alder reactions to afford carbocyclic chiral compounds with a sugar backbone. In 2008, Gagné introduced a Ni-mediated Negishi coupling to synthesize alkyl- and aryl-C-glycosides