Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• proceeded in reasonable yields while the diastereoselectivity strongly depends on the structure of the diene. An example of an intramolecular process as well as the use of furan and 1,4-cyclohexadiene as dienes are also reported. Keywords: cyclopropanation; cyclopropenes; dienes; divinylcyclopropanes

• substituted alkene, allowing the synthesis of 1,2-divinylcyclopropane 3k within the typical range of yields and cis/trans selectivities. Finally, 1,2,3-trisubstituted divinylcyclopropane 3l was prepared in 50% (cis/trans = 2.5:1) from cyclopropene 1a and (1E,3E)-1,4-diphenylbuta-1,3-diene through a

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• -derived precursors When Garner’s aldehyde (R)-5 prepared from D-serine was subjected to ZnCl2-catalyzed cyclocondensation with Danishefsky's diene a (>9:1) mixture of diastereoisomeric pyranones 6 was formed with the threo isomer 6a prevailing. Oxidative removal of two carbon atoms was followed by formate

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• -telechelic poly(1,4-butadiene) bearing alkoxyamine termini was obtained by ROMP of trans,trans,cis-1,5,9-cyclododecatriene in the presence of a symmetric acyclic olefin CTA (Scheme 2). This telechelic polybutadiene was used as the macroinitiator for the NMP of styrene and diene monomers to yield unimodal SBS

• multiple click reactions of the diazido-telechelic PBD with a dialkynyl-containing azobenzene chromophore. The newly formed triazole moieties can tune and improve the photoresponsive properties of PBD. α,ω-Functional telechelic polymers also can be synthesized by acyclic diene metathesis (ADMET

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• the syn diastereomer 18 in high stereoselectivity (93:7). After silylation of the free hydroxy group, the cleavage of the PMB ether with DDQ led to alcohol 20 in 77% yield for the two steps. Ring-closing metathesis of diene 21, obtained by O-vinylation of 20, gave the dihydropyran 22 in 53% overall

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• functional group and the substrate structure and may follow a different reaction course than what is usually observed. In cases where ROM–RCEYM occurred, the resulting 1,3-diene reacts in situ with the dienophile to provide condensed tetracyclic systems. Keywords: Diels–Alder reaction; domino process; enyne

• derivative 2 would provide the tricyclic 1,3-diene 3 which on Diels–Alder reaction with a dienophile would enable access to condensed polycyclic structures 4 (Scheme 2). Thus an appropriately chosen norbornene derivative and a dienophile may provide the B/C/D/E ring system of retigeranic acids. Herein we

• diene. Thus unlike metathesis of 7a, metathesis of its acetate analogue 7b occurred through a domino ROM–RCEYM process. Addition of the Ru-carbene 10 arising from ring opening of norbornene unit in 7b could add to the acetylenic unit of another molecule of 7b leading to copolymerization. However, this

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• substrates 11g and 11h containing ester and ketone moieties, respectively, which are generally more reactive toward nucleophiles than CO2. Notably, the Co-catalyst system was found to be applicable for the carboxylation of 1,3-diene derivatives 14 with CO2 (Scheme 12), which afforded various hexa-3,5-dienoic

• acid derivatives. Diene 14a was converted into the corresponding carboxylic acid 15a in good yield. In addition, 1,4-dienes having cyclohexenyl and geminal diphenyl substituents (14b and 14c) produced their corresponding linear carboxylic acids 15b and 15c in 78% and 57% yields, respectively. Substrate

• -catalyzed carboxylation of 11a. Scope of the carboxylation of allylarenes 11. Scope of the carboxylation of 1,4-diene derivatives 14. Plausible reaction mechanism for the Co-catalyzed C(sp3)–H carboxylation of allylarenes. Optimization of the Co-catalyzed carboxyzincation of 16a. Derivatization of the

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• species (Figure 1). However, the substrates employed have been restricted to allylarenes and 1,4-enyne, and 1,4-diene derivatives and α-olefins were totally unexplored. Therefore, the next challenge would be to use less reactive α-olefins (pKa value of 1-propene = 43). In this paper, we describe an

Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• results in the formation of a peculiar system of conjugated double bonds, which can potentially act as either oxo-diene or aza-diene (Figure 3). To the best of our knowledge, there is no example of the involvement of the aza-diene fragment of acyl(quinoxalin-2-yl)ketenes into intermolecular trapping by

• ]quinoxaline-1,2,4(5H)-triones III [23][56] (Scheme 1). According to the literature data, precursors I and II are unsuitable for achieving the proposed goal as the generated ketene IV reacts only at its oxo-diene fragment in intermolecular trapping reactions with various dienophiles [57][58][59][60][61][62

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• , the PMB-protected epoxide 121 was converted to diene 122. The dihydropyran ring of 123 was constructed by RCM of 122 catalyzed by a Grubbs 1st generation catalyst. The isomerization of the double bond in 123 by treatment with a Wilkinson catalyst under basic conditions afforded glycal 124 (Scheme 16

Lanyamycin, a macrolide antibiotic from Sorangium cellulosum, strain Soce 481 (Myxobacteria)

• Lucky S. Mulwa,
• Rolf Jansen,
• Dimas F. Praditya,
• Kathrin I. Mohr,
• Patrick W. Okanya,
• Joachim Wink,
• Eike Steinmann and
• Marc Stadler

Beilstein J. Org. Chem. 2018, 14, 1554–1562, doi:10.3762/bjoc.14.132

• . The only remaining NH group finally filled the gap between the amide C-27 (δC 171 ppm) and C-26 (δC 75 ppm) based on the HMBC correlation H-26/C-27 thus forming the unusual and unstable N-acyl hemiaminal that explains the interconversion of lanyamycin isomers 1 and 2. The E configuration of the diene

• double bonds Δ10,11 and Δ12,13 was recognized from their large coupling constants of about 15 Hz while 1H,1H-ROESY correlations between H-3 and H-5 as well as between methyl-37 and both methyl-38 and methoxy-36 suggested the E configuration of the substituted Δ2,3,Δ4,5-diene. Likewise, the E

• difference is the missing methyl group of the unsubstituted diene in 1/2. Further comparison of the NMR data revealed a significant lower 13C-shift of C-7 of about 5–6 ppm. Together with the missing vicinal coupling between H-7 and H-8 this indicated an inverted configuration of the secondary alcohol at C-7

Three-component coupling of aryl iodides, allenes, and aldehydes catalyzed by a Co/Cr-hybrid catalyst

• Kimihiro Komeyama,
• Shunsuke Sakiyama,
• Kento Iwashita,
• Itaru Osaka and
• Ken Takaki

Beilstein J. Org. Chem. 2018, 14, 1413–1420, doi:10.3762/bjoc.14.118

• coupling reaction between iodobenzene (1a), 5-phenylpenta-1,2-diene (2a), and 4-methylbenzaldehyde (3a) in the presence of CoBr2 (10 mol %), CrCl3 (20 mol %), and manganese powder (2.0 equiv), using trimethylsilyl chloride (TMSCl, 1.2 equiv) as a trapping reagent [7]. These results are summarized in Table

• good yields (Scheme 8). During the investigation of allenes, it was observed that, when oxygen substituents were present at the allenyl position, coupling products with reversed diastereoselectivity were obtained (Scheme 9). Thus, treatment of 4-benzyloxybuta-1,2-diene (5) with 1 and 3a under identical

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• methyl ester 120 in four steps (Scheme 39) [73]. The organocatalytic properties of this inherently chiral calixarene Brønsted acid was firstly examined in the aza-Diels–Alder reaction of imines bearing electron-withdrawing or electron-donating substituents 122 with Danishefsky’s diene (123, Scheme 40

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

• complete electron delocalization, whereas the carbonium ion 200 (and 201) formed from 190 indicated considerably less electron delocalization (Scheme 34). 3.2.3. Cycloaddition reactions: 2,3-Benzotropone (12) possesses a high functional tolerance towards both the diene and dienophile and undergoes the

Iodine(III)-mediated halogenations of acyclic monoterpenoids

• Laure Peilleron,
• Tatyana D. Grayfer,
• Joëlle Dubois,
• Robert H. Dodd and
• Kevin Cariou

Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96

• various functional groups (protected and free alcohols, amine, E and Z olefins, diene moiety) aimed at probing potential chemo-, regio- and stereoselectivity issues – were selected: geranyl acetate (1a), neryl acetate (1b), geraniol (1c), N-tosylgeranylamine (1d) and myrcene (1e, Figure 2). Results and

• in good yields. Finally, the reaction was performed on myrcene (1e), providing 2e in 78% yield and leaving the diene moiety untouched. Bromo(trifluoro)acetoxylation The success of the bromo(trifluoro)acetoxylation lies in the reverse addition protocol whereby the tetrabutylammonium bromide is slowly

• added to the suspension of the terpenoid and PIFA at 0 °C. In this manner, good to excellent yields (57–84%) were obtained for the formation of Z-derivative 3b, alcohol 3c [16], tosylamine 3d and diene 3e (Scheme 3). Once again, the selectivity is excellent as no reactions with the other double bonds or

Volatiles from three genome sequenced fungi from the genus Aspergillus

• Jeroen S. Dickschat,
• Ersin Celik and
• Nelson L. Brock

Beilstein J. Org. Chem. 2018, 14, 900–910, doi:10.3762/bjoc.14.77

• homolog of the geosmin synthase is encoded in the genome of A. fischeri or of any other fungus. Furthermore, the diterpene pimara-8(14),15-diene (7) was one of the main compounds in the bouquet of A. fischeri. The biosynthesis of this compound is a two-step process that requires cyclisation of

• from A by a 1,2-hydride shift to the homobisabolyl cation I, cyclisation to J, and deprotonation. The second group of biosynthetically related sesquiterpenes is composed of daucene (19), the main component in the headspace extracts from A. fischeri, and its congeners dauca-4(11),8-diene (17

• ), isodaucene (18), and trans-dauca-8,11-diene (20). The biosynthesis of these compounds requires isomerisation of FPP to NPP, followed by cyclisation to K that results in 17 and 18 by deprotonation (Scheme 3). A 1,2-hydride shift to L and loss of a proton explains the main product 19. For compound 20 a

Stepwise radical cation Diels–Alder reaction via multiple pathways

• Ryo Shimizu,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59

• one of the most powerful methods to construct six-membered ring systems. A “normal” Diels–Alder reaction must consider an electronic matching of the substrates, with an electron-rich diene and electron-deficient dienophile as the general combination. Although having both an electron-rich diene and

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

• , 70.62; H, 7.10; N, 1.90. Synthesis of macrocyclic compound 25 To a solution of diene 24 (85.0 mg, 0.060 mmol) in degassed, anhydrous toluene (10 mL), Hoveyda–Grubbs catalyst 2nd generation (3.7 mg, 0.006 mmol) was added, and the mixture was stirred and heated at 95 °C for 48 h. The mixture was

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• at 78 °C, [4 + 2] cycloaddition took place between the o-QM generated from the corresponding aminonaphthol as diene component and cyclic imines playing the role of heterodienophiles (Scheme 5). Fülöp and co-workers then extended their studies by applying both 2-aminoalkyl-1-naphthols and 1-aminoalkyl

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

• the amount of diene to 5 equiv, the HDA adducts 3ad–3cd and 3ae–3ce were obtained in moderate to good yields (3ad–3cd: 55–73%, 3ae–3ce: 49–65%; Table 2, entries 8–13). The HDA adducts 3ae–3ce derived from 2e were isolated as mixtures of regioisomers (distal:proximal = 2:1 or 1:1 as determined by 1H

Addition of dithi(ol)anylium tetrafluoroborates to α,β-unsaturated ketones

• Yu-Chieh Huang,
• An Nguyen,
• Simone Gräßle,
• Sylvia Vanderheiden,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2018, 14, 515–522, doi:10.3762/bjoc.14.37

• dithioacetal. The scope of the presented procedure is shown with four additional transformations including the use of additional electrophiles and nucleophiles, the use of a chiral auxiliary and subsequent reduction of selected products. Additionally, we extended the reaction to the synthesis of diene

• procedure for the synthesis of diene dithioacetals. A similar reaction using α-carbonyl substituted ketene dithioacetals for an addition to alkynes under iron catalysis was shown by Liu et al. before and was used for the synthesis of δ-lactams and lactones by 6-endo annulation [35]. Our approach reveals

• that comparable reactions of α-alkyl or aryl-substitued dithiolanylium TFBs can be used for the reaction with ynones giving diene dithioacetals as compounds 18a and 18b in a related manner (Scheme 6). Conclusion The presented study shows that some of the current challenges concerning the addition of

Continuous multistep synthesis of 2-(azidomethyl)oxazoles

• Thaís A. Rossa,
• Nícolas S. Suveges,
• Marcus M. Sá,
• David Cantillo and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2018, 14, 506–514, doi:10.3762/bjoc.14.36

• ]. Sulfamoxole is a broad-spectrum antibiotic for the treatment of bacterial infections (Figure 1b) [8]. In addition, ongoing studies show the potential of amino and amido-oxazoles to act as fluorescent dipeptidomimetics (Figure 1c) [9]. Due to their diene character, oxazoles find also use as intermediates in

Gram-scale preparation of negative-type liquid crystals with a CF₂CF₂-carbocycle unit via an improved short-step synthetic protocol

• Tatsuya Kumon,
• Shohei Hashishita,
• Takumi Kida,
• Shigeyuki Yamada,
• Takashi Ishihara and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 148–154, doi:10.3762/bjoc.14.10

• ., the 5,5,6,6-tetrafluorocyclohexa-1,3-diene [12] or the 1,1,2,2-tetrafluorocyclohexane motif [13], were successfully synthesized and found to exhibit a large negative Δε value (−7.3 for 1c and −9.4 for trans-2c) [14]. This indicated that these compounds are promising candidates for vertical alignment

• . The latter could be constructed through ring-closing metathesis of the corresponding precursor, e.g., 4,4,5,5-tetrafluoroocta-1,7-diene 5, using a Grubbs' catalyst. The octa-1,7-diene 5 could be obtained through a nucleophilic addition of a vinylic Grignard reagent to the γ-keto ester 6. Lastly, the γ

• afford the corresponding octa-1,7-diene 5a in only 46% yield. In this case, the 5-membered lactol derivative 8a was also obtained in 42% yield as a side-product. A proposed reaction mechanism for the formation of 5a and 8a is shown in Scheme 3. Thus, the nucleophilic addition reactions of vinylmagnesium

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

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

• and ethyl esters were determined by X-ray crystallography [19]. The X-ray structure of the Pt(II) chelate of tetramethyl 2,6,9-trioxabicyclo[3.3.1]nona-3,7-diene obtained from tris-acetylacetonato platinum(II) was determined previously [22][23], and the separation of the enantiomers of the free ligand

• was achieved by fractional crystallization [24]. Chirality of the bisdioxine dicarbaldehyde, 2,6,9-trioxabicyclo[3.3.l]nona-3,7-diene-4,8-dicarbaldehyde, obtained by extrusion of water from triformylmethane, has also been demonstrated [25], and X-ray crystallography confirmed the structure of this

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• . Notably, diethyl 2,2-diallylmalonate as a diene gave the cyclised product resulting of a radical cascade. It has to be noticed that the reactions were conducted in the presence of 2 equivalents of trifluoroacetic or p-toluenesulfonic acid; yet, there was no mention of hydrotrifluoromethylated side

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

• reported by Fuchs, who obtained 1,3-cyclohexadienes 54 by reaction of 1,3-butadienyltriphenylphosphonium bromide with enolate anions 53 derived from aldehydes or ketones in yields of 35–57% (Scheme 36). The nucleophilic attack here was directed at position 4 of the diene [11]. Hewson and MacPherson