Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• product 11 (64%). Having the trimerized product 11, we attempted to open the norbornene system due to the fact that not all norbornene rings open up during RCM to generate propellane derivative. After allylation, RCM is not a clean reaction and it gave a mixture of the C3-symmetrical compounds. Therefore

• -allylation in the presence of NaHMDS (1 M solution in THF) at −75 °C to deliver the hexaallyl derivative 20 in 84% yield. Then, RCM in the presence of G-II catalyst in CH2Cl2 under nitrogen atmosphere gave the propellane moieties bearing C3-symmetric product 21 in good yield (91%). Its structure was

• . Synthesis of hexaallyl product 20 Based on the earlier procedure of allylation, compound 19 (336 mg, 0.29 mmol) was treated with NaHMDS (2.3 mL of 1 M solution in THF, 2.39 mmol) and allyl bromide (0.14 mL, 1.93 mmol) for 17 h to deliver hexaallyl product 20 after silica gel column chromatography (20% EtOAc

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• diiodobenzene 11 using allylboronate ester 12 via a SM-type allylation sequence [32]. Next, compound 13 was exposed to Grubbs 1st generation (G-I) catalyst 1 to effect the ring-closure to produce tetrahydronaphthalene derivative 14 (92%). Subsequently, aromatization of compound 14 was accomplished with 2,3

• respect, the key building block 29 was derived by employing a sequential O-allylation and CR, then again O-allylation, and CR [35] starting with a commercially available 6-bromo-2-naphthol (27). Subsequently, the diallyl derivative 29 was exposed to G-II catalyst 2 to deliver a ring-closure product 30 (83

• derivative 75 [41]. To this end, iodoacetanilide 71 was subjected to SM coupling in the presence of allyboronate ester 12 to give ortho-allylacetanilide (72), which was further modified by N-allylation with allyl bromide (28) to offer a mixture of diallyl compound 73a (82%) and isomerized product 73b (8

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

• Negishi coupling with aryl bromide, affording the corresponding sterically congested alkene 17b-Ar in 56% yield after two steps. The Negishi coupling with benzyl chloride and the Cu-catalyzed allylation of allyl bromide also afforded the corresponding products 17b-Bn and 17b-Allyl, respectively, in good

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• . Co(III)-catalyzed switchable hydroarylation of alkyl alkenes with indoles. Co(III)-catalyzed C2-allylation of indoles. Co(III)-catalyzed ortho C–H alkylation of arenes with maleimides. Co(III)-catalyzed hydroarylation of maleimides with arenes. Co(III)-catalyzed hydroarylation of allenes with arenes

Bi-mediated allylation of aldehydes in [bmim][Br]: a mechanistic investigation

• Mrunesh Koli,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2018, 14, 2198–2203, doi:10.3762/bjoc.14.193

• temperature ionic liquid (RTIL), [bmim][Br] has been found to be a superior medium for the Bi-mediated Barbier-type allylation of aldehydes compared to other conventional solvents. It plays the dual role of a solvent and a metal activator enabling higher yields of the products in a shorter reaction time using

• stoichiometric/near-stoichiometric amounts of reagents. Plausibly, [bmim][Br] activates Bi metal by a charge transfer mechanism. The 1H VT-NMR studies suggested that both the allylating species, allylbismuth dibromide and diallylbismuth bromide, are generated in situ. Keywords: allylation; bismuth; [bmim][Br

• ]; ionic liquid; Introduction The metal-mediated Barbier-type allylation of aldehydes has drawn considerable attention, because the resultant homoallylic alcohols are versatile intermediates for natural product synthesis [1][2][3][4][5][6][7]. The reaction, carried out in organic solvents, water, mixed

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• cyclopentane 5, a functionalized key intermediate, is presented. Compound 5 is involved in hydrolysis, α-allylation at C-8 and α-methylation at C-10 stereoselectively from the convex face. Then it is subjected to cross metathesis to give α,β-unsaturated ketone 11 as precursor in the total synthesis of

• hyperireflexolide A. Keywords: alkylation; allylation; cross metathesis; hyperireflexolide A; spiroterpene; Introduction Hyperireflexolide A (1) [1] is a spiroterpenoid, isolated from hypericum reflexum, plants of the genus hypericum (Figure 1). Hyperireflexolide A is widely used in folk medicine, displays

• with 2-bromopropene followed by lactonization. Enone 3 could be synthesized from 4 by installation of the methyl group at C-10 followed by cross metathesis reaction. Compound 4 could be obtained from the γ-lactone-fused cyclopentane 5 by deprotection of C-9 followed by allylation at C-8. Previously, we

Cobalt-catalyzed C–H cyanations: Insights into the reaction mechanism and the role of London dispersion

• Eric Detmar,
• Valentin Müller,
• Daniel Zell,
• Lutz Ackermann and
• Martin Breugst

Beilstein J. Org. Chem. 2018, 14, 1537–1545, doi:10.3762/bjoc.14.130

• ) to yield complex 5a. In contrast to previous computational studies on manganese(I)-catalyzed fluoro-allylation reactions where β-fluoride and HF eliminations played an important role [41], similar reactions involving amine eliminations seem to be not relevant in this reaction. Furthermore, a

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

• selectivity of ortho-lithiation could be tuned by changing the alkyllithium reagent employed. The performance of four inherently chiral bidentate calix[4]arene ligands in the asymmetric Tsuji–Trost allylation reaction (Scheme 10) has been evaluated and compared to that of the planar model ligands. Inherently

• applied in the palladium-catalyzed Tsuji–Trost allylation reaction. BINOL-derived calix[4]arene-diphosphite ligands. Inherently chiral calix[4]arene 43 containing a diarylmethanol structure. Calix[4]arene-based chiral primary amine–thiourea catalysts. Novel prolinamide organocatalysts based on the calix[4

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

• Romain Sallio,
• Stéphane Lebrun,
• Frédéric Capet,
• Francine Agbossou-Niedercorn,
• Christophe Michon and
• Eric Deniau

Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46

• with a tert-butyl increased significantly the diastereoselectivity of the reaction with 62% de (Table 2, entry 3). No de improvements resulted from the use of catalysts 18d,e which were modified by methylation or allylation of the cinchoninium alcohol fragment (Table 2, entries 4 and 5). While using

Synthesis of 2-aminosuberic acid derivatives as components of some histone deacetylase inhibiting cyclic tetrapeptides

• Shital Kumar Chattopadhyay,
• Suman Sil and
• Jyoti Prasad Mukherjee

Beilstein J. Org. Chem. 2017, 13, 2153–2156, doi:10.3762/bjoc.13.214

• to provide the desired 2-aminoheptenoic acid derivative 11. Several syntheses of this important amino acid have appeared which include Lubell’s palladium-catalyzed allylation [15], Riera’s asymmetric epoxidation protocol [16], Rich’s enolate amination [17] and Hruby’s asymmetric alkylation [18] of a

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

Effect of uridine protecting groups on the diastereoselectivity of uridine-derived aldehyde 5’-alkynylation

• Raja Ben Othman,
• Mickaël J. Fer,
• Laurent Le Corre,
• Sandrine Calvet-Vitale and
• Christine Gravier-Pelletier

Beilstein J. Org. Chem. 2017, 13, 1533–1541, doi:10.3762/bjoc.13.153

• )ide derivative syntheses is obtained in a very satisfactory 61% yield over two steps. Experimental General procedure for N3-allylation of protected uridine derivatives. To a solution of protected uridine derivative (1 equiv) in DMF/acetone (1:1, final concentration 0.4 M) was added K2CO3 (1.8 equiv

A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E

• Marcel Reimann,
• Louis P. Sandjo,
• Luis Antelo,
• Eckhard Thines,
• Isabella Siepe and
• Till Opatz

Beilstein J. Org. Chem. 2017, 13, 1430–1438, doi:10.3762/bjoc.13.140

• hydride, followed by Fmoc-protection and ozonolysis furnished aldehyde 5 in 57% yield over three steps (Scheme 2). The homoallylic alcohol was prepared by an enantioselective Duthaler–Hafner allylation [13] with the titanium-complex 15 in high yield and 94% ee. Attempts to perform a catalytic Keck

• allylation with BINOL-titanium catalysts failed due to low conversion [14]; however, in spite of good experience with the Maruoka–Keck allylation in another total synthesis, the conversion was not satisfying in this case [15]. After protection and guanidinylation with triflylguanidine 14, the homoallylic

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• position possibly lowers the reactivity of the iodine in the oxidative addition step in the catalytic cycle. For the synthesis of stannane 56 the authors could benefit from the previous fragment synthesis. In 2010 they first published an approach to an eastern building block through an allylation

Synthesis of new pyrrolidine-based organocatalysts and study of their use in the asymmetric Michael addition of aldehydes to nitroolefins

• Alejandro Castán,
• Ramón Badorrey,
• José A. Gálvez and
• María D. Díaz-de-Villegas

Beilstein J. Org. Chem. 2017, 13, 612–619, doi:10.3762/bjoc.13.59

• organocatalysts with a bulky substituent at C2 were synthesized from chiral imines derived from (R)-glyceraldehyde acetonide by diastereoselective allylation followed by a sequential hydrozirconation/iodination reaction. The new compounds were found to be effective organocatalysts for the Michael addition of

• obtained by the addition of allylmagnesium bromide to imines derived from (R)-glyceraldehyde acetonides A (Figure 1) according to our previously described methodology [15]. The configuration at C2 of the pyrrolidine ring would be determined in the diastereoselective allylation of the starting chiral imines

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• bond donor by Tan and co-workers [91]. Allylation of benzylic alcohols by Takemoto and co-workers [92]. NIS induced semipinacol rearrangement via C–X bond cleavage [93].

Chromium(II)-catalyzed enantioselective arylation of ketones

• Gang Wang,
• Shutao Sun,
• Ying Mao,
• Zhiyu Xie and
• Lei Liu

Beilstein J. Org. Chem. 2016, 12, 2771–2775, doi:10.3762/bjoc.12.275

• addition reactions mainly focused on allylation, propargylation, alkenylation and alkylation of aldehydes [10][11]. Since the first example of enantioselective allylation of aldehydes catalyzed by a Cr(II)–salen complex in 1999 by Cozzi and co-workers [12], several elegant catalytic enantioselective

• allylation and propargylation reactions have been developed by the groups of Nakada [13][14], Berkessel [15], Kishi [16], Sigman [17], Yamamoto [18], Guiry [19], Chen [20], Gade [21], White [22], and Zhang [23][24][25], respectively. The alkenylation and alkylation reactions were mainly explored by the Kishi

• with high enantioselectivity (up to 95% ee) [38][39][40][41]. After that, the Chen group also disclosed enantioselective allylation of ketones using spirocyclic chiral borate and chiral bipyridyl alcohol ligands with the ee value ranging from 27% to 97% [42][43]. However, as far as we know, a Cr

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• saccharide alcohols [34], the first catalytic tin-mediated procedure for regioselective benzylation/allylation of hydroxy groups incorporated into vicinal diols [35], and three alternative acetalation protocols [36]. Besides the avoided use of solvents, these approaches appear advantageous owing to their

• previously performed better than pyridine in the tin-catalyzed solvent-free regioselective benzylation or allylation of sugars [35]. The silylation rate was not appreciably influenced by tin catalysis (compare entries 2 and 3 in Table 1), although a previous report described the stoichiometric use of

• -catalyzed procedure for benzylation/allylation of saccharide secondary alcohols [35] with the present protocol for silylation of primary alcohols. Some experiments were carried out on methyl mannoside (1) in order to establish which order of steps (alkylation/silylation or the reverse sequence) might be

Et₃B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

• Ahlem Abidi,
• Yosra Oueslati and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

• Ahlem Abidi Yosra Oueslati Farhat Rezgui Université de Tunis EL Manar, Laboratoire de Chimie Organique Structurale et Macromoléculaire, Faculté des Sciences Campus Universitaire, 2092 Tunis, Tunisia 10.3762/bjoc.12.234 Abstract A practical and efficient palladium-catalyzed direct allylation of β

• allylation of a variety of active methylene compounds [29], aldehydes [30], ketones [31], and imines [32] with only common allylic alcohols. As part of an ongoing program studying the behavior of MBH derivatives [33] towards β-dicarbonyl compounds, our research group [34][35][36][37] has reported an

• of the MBH carboxylates with aliphatic 1,3-diketones in the presence of K2CO3. A drawback of these synthetic approaches is the need to first perform the acylation step of the corresponding allyl MBH alcohols. For this reason, we herein report an efficient direct method for the allylation of β

Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides

• Shuai Qiu,
• Choon-Hong Tan and
• Zhiyong Jiang

Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222

• [6], allylation [7], conjugate addition to enones [8], and γ-addition with allenoates [9]. All these examples focused on nucleophilic addition reactions of the C5 atom of 5H-thiazol-4-ones. Recently, we described an organocatalytic asymmetric [4 + 2] cyclization of 5H-thiazol-4-ones with a series of

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• . Enantioconvergent synthesis of phosphines governed by Curtin–Hammett/Winstein–Holness kinetics (TMS = trimethylsilyl, Is = 2,4,6-triisopropylphenyl). Stoltz’ stereoablative oxindole functionalization. Fu’s type II enantioconvergent Cu-catalyzed photoredox reaction. Stereoablative enantioconvergent allylation and

Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2016, 12, 1877–1883, doi:10.3762/bjoc.12.177

• ring-closing metathesis (RCM) [24][25][26][27][28][29][30][31][32]. Whereas, the diallyl derivative 2 can be derived from a readily available Diels–Alder (DA) adduct 3 through an allylation sequence. Results and Discussion Installation of two C–C bonds to generate quaternary centers in a

• in Figure 2. At this point, we turned our attention to understand the configurational origin of the allyl groups in 2a. To understand whether compound 2a was formed by Claisen rearrangement (CR) of the corresponding O-allyl compound or by carbanion mediated C-allylation of the DA adduct 3a, we

• X-ray diffraction analysis. A control experiment with propyl bromide provided an insight into the reaction mechanism that the bridgehead allylation proceeds through enolization, O-allylation followed by CR and not via carbanion chemistry. This alternative strategy is useful to introduce vicinal

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• elaboration and functionalization. A few substrates were treated under decarboxylative allylation (DcA) conditions in the presence of 10 mol % of Pd(PPh3)4 in refluxing tetrahydrofuran (7–8 h), which afforded products 26a–d in up to 99% yield (Scheme 11). Interestingly, oxidative coupling products with

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• already been reported in preliminary form [31]. Homoallylic amines of type 12 may be efficiently obtained through multicomponent reactions. These involve the nucleophilic allylation of imines which may be generated in situ by the condensation of an amine and a carbonyl compound. As shown in Scheme 2, two

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• metal-catalyzed synthesis The chiral ligand/metal complexes have been widely employed in catalytic asymmetric synthesis of enantioenriched 3-hydroxyoxindoles, achieving good to excellent enantioselectivities and high yields. Pd-catalyzed allylation of isatins The palladium catalyst is widely used in

• organic synthesis and has showed its usefulness in the allylation of isatins. In 2014, Song and co-workers designed the chiral CNN (three atoms attched to the palladium) pincer Pd complexes, which were proved to be efficient in catalyzing the enantioselective allylation of isatins with allyltributytin

• allylated product in 93% yield and 72% ee value when cat. 2 was used (Scheme 2). Kesavan and co-workers described that the Pd/bis(oxazoline) (L1) complex can catalyze the asymmetric allylation of 3-O-Boc-oxindole, yielding the 3-allyl-3-hydroxyoxindoles in good yields (up to 93% yield) and with high