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

• by manipulations of 5. After acetal hydrolysis and the subsequent hydride reduction, 4-thioarabinose derivative 9 was obtained in good yield. Introduction of a TBDPS group at the primary hydroxy group of 9, oxidation and Wittig reaction, followed by deprotection of the benzyl group, gave allyl

• be formed by E1 elimination of the allyl cation intermediate. The fact that 96a and 96b showed different reactivities could be explained by the steric interaction between the substituents on the cyclohexene ring and the nucleobase approaching. Compounds 97a–d were converted to the corresponding

• , the C–N bond-forming reactions using hypervalent iodine agents have attracted much attention [62][65][66][67][68]. In the case of the hypervalent iodine-catalyzed coupling reaction with allylsilanes (Figure 5), the reaction involves the following 2 steps: 1) the generation of allyl cation 87 by the

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• with allyl or propargyl bromide to obtain C12 and C13. In another way, cinchonidine was reduced by H2/Pd/C to yield dihydrocinchonidine, and then reacted with 4-trifluoromethylbenzyl bromide to obtained C14. C15 was prepared from cinchonidine via bromination, debromination and condensation with 4

• the mono-substituted counterparts (C6 and C7). The derivatives (C12–C15) of C7, the best one so far, were further studied. When the hydroxy group in C7 was protected by an allyl or a propargyl group, racemic product was obtained (Table 1, entries 12 and 13). This suggested that the free hydroxy group

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

• transition state C of the carbocobaltation step (Scheme 11), facilitating the further selective formation of the branched allylcobalt species D which could be converted into the thermodynamically more stable (E)-allylcobalt species E because of the flexible C(vinyl)–C(allyl) single bond. The generated

• addition of an aryl iodide 1 to a low-valent cobalt species to form an arylcobalt species G that reacts with an allene 2 to stereoselectively generate an allylcobalt H via carbocobaltation. Rapid transmetalation between H and the chromium salt [8][9] triggers the transfer of the cobalt allyl group to the

• chromium to afford I and the highly nucleophilic allylchromium species J, which retains the same stereochemical information on the olefinic moiety as that of H. The allylchromium species J reacts with the aldehyde 3 at the γ-position of the allyl metal unit via a cyclic six-membered transition state K to

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

• anion with the two hydroxy groups of the calixarene ligand to selectively direct the nucleophile towards one carbon atom of the π-allyl intermediate in the presence of potassium cations. In 2009 and 2010, Arnott et al. utilized a chiral isopropyloxazoline as an ortho-lithiation directing group in order

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• moderate to good yields (48–83%). Generally, the highest yields (68–83%) were achieved in the reactions of N-benzylisatin imines (R2 = Bn) while N-allyl, N-phenyl and N-prenyl-substituted ones led to the corresponding products in 48–70% yields. Interestingly, the authors found that using 20 mol % of α

• enantioselectivities (96–99% ee) were achieved with variously N-alkyl substituted isatin imines (R3 = Bn, allyl, Me, MOM). The scope of this unprecedented methodology was extended to 2-naphthols 44 which required 10 mol % of catalyst loading to provide the optimal results. In these conditions, the reaction with a

• yields (46–98%) and uniformly excellent enantioselectivities (94–98% ee), as shown in Scheme 17. Comparable results were achieved for N-benzyl, N-phenyl, N-allyl and N-methyl-substituted isatin imines (R3 = Bn, Ph, allyl, Me). Moreover, various electron-donating or electron-withdrawing groups were

Novel unit B cryptophycin analogues as payloads for targeted therapy

• Eduard Figueras,
• Adina Borbély,
• Mohamed Ismail,
• Marcel Frese and
• Norbert Sewald

Beilstein J. Org. Chem. 2018, 14, 1281–1286, doi:10.3762/bjoc.14.109

• column chromatography. The allyl ether in 23 was cleaved using Pd(PPh3)4 as Pd(0) source and phenylsilane as scavenger to obtain the cryptophycin analogue 24 in good purity. Biological evaluation The biological activity of the modified unit B analogues was determined in a cell viability assay using the

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

• exchange/coupling sequence through the iodosyl intermediate 116 can be an alternative pathway for the formation of 115. Likewise, a C–C ipso–allyl ligand coupling via intermediate 120 from O-naphtholate 118 explains the formation of product 119. Conclusion To conclude, throughout this review we have seen

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

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

• Cyrus Mowdawalla,
• Faiz Ahmed,
• Tian Li,
• Kiet Pham,
• Loma Dave,
• Grace Kim and
• I. F. Dempsey Hyatt

Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91

• metal-like properties of iodine(III) were particularly significant in the development of the reaction reported in this communication [15][16]. A commonality in the RICR is that the proposed mechanisms involve an unstable allyl or propargyl hypervalent iodine intermediate. To the best of our knowledge

• , no allyl, propargyl, or alkyl hypervalent iodine species have been isolated at room temperature (besides fluorinated alkyl chains [17]), thus trapping an intermediate to validate the mechanism seemed unlikely. The process in which these hypervalent iodine intermediates form from metalloid substituted

Hypervalent iodine-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• alkene functionalization utilizing a PhI(OAc)2 ((diacetoxyiodo)benzene, PIDA)/Lewis acid combination in order to access isoxazoline and pyrazoline cores. Based on allyl ketone oximes and allyl ketone tosylhydrazones, we have developed an alkene oxyamidation and amido-amidation protocol en route to

• unactivated olefins provides a rapid construction of different heterocycles [16][17]. More specifically, the formation of isoxazoline and pyrazoline cores via alkene heterofunctionalization of allyl ketone oximes and/or allyl ketone tosylhydrazones has been well documented [18][19][20][21][22]. For example

• combination with electron-rich, Brønsted basic amines were converted to their corresponding indoline and azaindoline derivatives. However, an attempted expansion of this methodology to allyl ketone oximes and allyl ketone tosylhydrazones proved unsuccessful under the previously reported reaction conditions

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

• Zhensheng Zhao Graham K. Murphy Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, N2L3G1, ON, Canada 10.3762/bjoc.14.67 Abstract Allyl and vinyl chlorides represent important structural motifs in organic chemistry. Herein is described the chemoselective and

• materials [7][8]. And as there is an abundance of chlorine-containing natural products, the synthesis of chlorinated functional groups, such as allyl- and vinyl chlorides, can represent challenging obstacles that practitioners of natural product synthesis must surmount [9][10][11][12]. More commonly, allyl

• - and vinyl chlorides are highly sought-after intermediates for effecting allylations, and for use in transition metal-catalyzed carbon–carbon and carbon–heteroatom bond-forming reactions [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Given the versatility of allyl chloride and β

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• -dideazaadenine to obtain the lactol intermediate (Figure 7A) [63][65][69][70]. Deoxygenation of the lactol intermediate by BF3·OEt2 resulted in the oxocarbenium ion, which was then reduced using triethylsilane to obtain 2. Replacing triethylsilane with allyl trimethylsilane and trimethylsilyl cyanide gave C1

• '-allyl (3) and C1'-cyano (4) substitutions respectively. A β/α ratio of 95:5, 87:13 and 89:11 was observed for 2, 3 and 4, respectively, which was sensitive to the reaction temperature and the reagents used [69][70]. A marked difference in diastereomeric purity was observed when the open form of the

• (compound 23) is shown in Figure 9, which involves installing an allyl group at C1' (20) and converting the C2'–CN to an aldehyde (21) followed by a Wittig reaction to install a second allyl group at C2' (22). Second generation Grubb’s catalyst was used for the ring formation, followed by hydrogenation to

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

• unstable [Pd(allyl)Cl]2 intermediate from air. Micelles were also used to perform cross-coupling between benzyl and aryl halides in water [65]. This reaction is known to result in very limited yields due to the undesired homo-coupling reaction between electron-rich and electron-poor benzyl bromides [69

• hydrogenation in water. By using only 0.01% of palladium at room temperature, the hydrogenation of allyl alcohol was realized [101]. DSNs were recycled for up to 10 times without loss in activity. DSN nanoreactors were later shown to be utilized for catalysing Suzuki coupling reactions between PhB(OH)2 and PhX

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes

• Anna-Lena Dreier,
• Andrej V. Matsnev,
• Joseph S. Thrasher and
• Günter Haufe

Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25

• with benzaldehyde, p-nitro-, and p-methoxybenzaldehyde as described recently by Ponomarenko and Röschenthaler et al. [34]. Considering our earlier results [31] on TMSOTf-mediated Claisen-type rearrangements of SF5-acetates of allyl alcohols, we favor the initial formation of (Z)-enolates (ketene

Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)

• Michał Nowacki and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14

• when the σH-adducts, obtained from an allyl sulfone carbanion, were treated with a silylating agent or a Lewis acid [24]. In a similar reaction σH-adducts of benzyl carbanions of arylacetonitriles upon treatment with trialkylchlorosilanes yielded 9-cyanoacridines [25]. This [3 + 3] annulation leading

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• types of CF3-containing molecules. Traditional methods that were described for the preparation of CF3-containing molecules required harsh reaction conditions and pre-functionalized starting materials such as allyl bromides or fluorosulfones. The past years had witnessed many advances in constructing

• CF3 source in allylic trifluoromethylation (Scheme 30). It was found that allyl substrates bearing an aromatic moiety showed relatively low efficiency. At the same year, the group of Li [51] achieved a copper-catalyzed trifluoromethylation via oxidation of C(sp3)–H bonds adjacent to nitrogen atom in

Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)

• Tao Wang,
• Kathrin I. Mohr,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9

• File 1) were identical to previously reported data [38]. The allyl alcohol 26 was also used in a Sharpless epoxidation with (−)-D-DET to give 27b that was converted into (4S,5R,6S)-11d via the same sequence of steps with a total yield of 6% via seven steps. Starting from the alcohol 24, two more

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

• of allyl and vinyl sulfones In 2015, our laboratory reported the first metal-free visible-light photoredox-catalyzed method for the preparation of vinyl sulfones from the respective aryl sulfinate salts (Scheme 42a) [77]. Eosin Y was applied as photocatalyst to produce a diverse scope of vinyl

• later, Lei and co-workers reported a photocatalyzed oxidant-free method for the preparation of allyl sulfones from sulfinic acids and α-methylsytrenes, applying Eosin Y as organic photocatalyst and avoiding any sacrificial additives or oxidants (Scheme 45) [82]. They successfully applied the proton

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

• (prepared from O-benzyl-protected glucose and glutaric anhydride) was introduced at the free 6’-OH group using DCC and DMAP to give 22. The anomeric allyl group was cleaved by standard procedure, the phosphorylation of the 1-OH group was performed by 1-O-lithiation and subsequent treatment with tetrabenzyl

• ) [90], followed by protection of the liberated 2-amino group by reaction with (R)-3-benzyloxycarboxylic acid using O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU) and DMAP as coupling reagents which furnished triacylated precursor 29. The 1-O-allyl group was then

• microfluidic conditions applied by the authors ensured even better stereoselectivity and higher yields [21]. Sequential protective group manipulation and N-acylation procedure furnished the lipid A precursor 37. The isopropylidene and anomeric allyl groups in 37 were removed and the anomeric position in 38 was

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

• Katrina Tait,
• Alysia Horvath,
• Nicolas Blanchard and
• William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

• nucleophile, the yield was decreased to 42% (Table 3, entry 4) while using isobutyl alcohol produced a similar yield of 41% (Table 3, entry 5). Using 2-methylbutanol produced a 34% yield of a 1:1 diastereomeric ratio of product (Table 3, entry 6) and using allyl alcohol produced ring-opened product 26g in a

Synthetic mRNA capping

• Fabian Muttach,
• Nils Muthmann and
• Andrea Rentmeister

Beilstein J. Org. Chem. 2017, 13, 2819–2832, doi:10.3762/bjoc.13.274

• the cap-binding protein eIF4E. Microscale thermophoresis revealed that these crosslinker-modified caps still bound to eIF4E, albeit with strongly decreased affinity. Translation was highly susceptible to modifications at the N7-position of the mRNA cap. While for N7-allyl or N7-azidobutenyl

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

• /cyclisation processes, as demonstrated by Miyabe and co-workers [27]. Thus, in typical photoredox catalysis conditions, N-allyl-N-(benzyloxy)methacrylamide 23 could undergo the addition of the CF3 radical, followed by a cyclisation step and a final chlorine abstraction to yield the corresponding cyclic

• compound, albeit in low yield and with poor regio- and diastereoselectivity (Scheme 19). Interestingly, the authors proposed a mechanism involving a chain propagation pathway, in contrast to the work of Jung and Han. A similar cascade reaction was also performed on diethyl 2-allyl-2-(3-methylbut-2-en-1-yl

• moiety and a Cl atom onto alkenes. Chlorotrifluoromethylaltion of terminal, 1,1- and 1,2-substituted alkenes. Chorotrifluoromethylation of electron-deficient alkenes (DCE = dichloroethane). Cascade trifluoromethylation/cyclisation/chlorination of N-allyl-N-(benzyloxy)methacrylamide. Cascade

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

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

• Wehman (Scheme 4) [10]. Vinylphosphonium salts can also be prepared by alkylation of phosphines (usually triphenylphosphine) with allyl halide derivatives and isomerization of allylphosphonium salts 4 thus obtained under the influence of bases such as triethylamine or sodium carbonate (Scheme 5) [11][12

• phosphorus ylides from vinylphosphonium salts. Intramolecular Wittig reaction with the use of vinylphosphonium salts. Alkylation of diphenylvinylphosphine with methyl or benzyl iodide. Methylation of isopropenyldiphenylphosphine with methyl iodide. Alkylation of phosphines with allyl halide derivatives and

A Brønsted base-promoted diastereoselective dimerization of azlactones

• Danielle L. J. Pinheiro,
• Gabriel M. F. Batista,
• Pedro P. de Castro,
• Leonã S. Flores,
• Gustavo F. S. Andrade and
• Giovanni W. Amarante

Beilstein J. Org. Chem. 2017, 13, 2663–2670, doi:10.3762/bjoc.13.264

• desired products in excellent yields and with up to dr >19:1 (products 2c, 2d and 2h). Substrates bearing an alkyl chain as an R1 group were well tolerated (2a and 2b). Importantly, azlactones containing a thioether or allyl substituents could be also accessed in good isolated yields (2f and 2g). The