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

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• -catalyzed allylation substitution reaction of oxazol-4(5H)-ones and thiazol-4(5H)-ones to afford enantioenriched tertiary alcohols and thioethers (Scheme 19) [42]. In this case the diastereoselectivity is controlled by cations, in contrast to most of the described protocols wherein it is modulated by anions

• . The authors found that whilst the best results for allylation of oxazol-4-(5H)-ones were achieved from zinc enolates, thiazol-4-(5H)-ones produced the best outcome when the magnesium enolate was used. After optimization it was shown that the reaction was efficient with different cinnamyl tert-butyl

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• -trimethylphenol analogously to the procedure described for 2,2,5,8-tetramethyl-6-chromanol by Dean [27]. 2,3-Dihydroxy-1,4-dioxane was obtain according to Venuti [37]. Substrates for testing catalysts in RCM reactions were prepared by allylation of commercial diethyl malonate with allyl bromide and/or 3-chloro-2

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• could be readily prepared from ortho-bromophenol (9, Scheme 2). O-Allylation of 9 followed by Lewis acid-mediated Claisen rearrangement afforded ortho-allylphenol 11, whose olefin moiety was ozonolyzed and subsequently treated with Wittig reagent 13 to provide amide 7 in 55% yield over four steps from 9

Recent developments in copper-catalyzed radical alkylations of electron-rich π-systems

• Kirk W. Shimkin and
• Donald A. Watson

Beilstein J. Org. Chem. 2015, 11, 2278–2288, doi:10.3762/bjoc.11.248

• nitronate anions are known to undergo alkylation with alkyl radicals, these radicals are often accessed using highly undesirable methods such as stoichiometric alkylmetal reagents or highly complex alkylating agents [17]. Although allylation [18][19][20][21][22][23] and arylation [24][25][26] of

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• compound 38 as the key starting synthone, easily prepared from 36 via an N-allylation sequence. Next, diallyl compound 38 was treated with catalyst 2 to deliver the expected bipiperidine derivative 39 in 60% yield. Further, this protocol has been extended to various oxygenated systems (Scheme 5). Snapper

• required building block 85 has been prepared from compound 84 by allylation with allyl bromide (37). Later, the pyran derivative 85 was treated with catalyst 2 to generate the bicyclic system 86 (73%) (Scheme 17). They also demonstrated a RCM–ROM–RCM cascade using a strain-free allyl heterocycle as useful

• derived from cyclopentadiene (111) and 1,4-benzoquinone. The diol 132 was produced by reduction of 131 in an efficient manner. To this end, the bis-O-allylated compound 133 was prepared by an allylation sequence using allyl bromide (37) in the presence of NaH starting with the diol 132, whereas compound

Design and synthesis of propellane derivatives and oxa-bowls via ring-rearrangement metathesis as a key step

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1727–1731, doi:10.3762/bjoc.11.188

• from readily accessible starting materials such as p-benzoquinone, 1,4-naphthoquinone and 1,4-anthraquinone. Keywords: allylation; propellane derivatives; quinones; ring-rearrangement metathesis; Introduction The synthesis of complex target structures requires bond-disconnection analysis of the

• propellane derivatives and oxa-bowls is shown in Figure 1. Oxa-bowl 1 can be synthesized from the tetracyclic compound 2 using RRM, which could be obtained from the known DA adduct 3 by O-allylation. On the other hand, the propellane derivative 7 may be synthesized from the tetraallyl compound 6 by a RRM

• sequence. Further, the tetraallyl compound 6 can be assembled from the C-allyl derivative 4 via reduction followed by O-allylation. The C-allyl derivative 4 may be obtained from the known DA adduct 3 by a C-allylation sequence which in turn could be prepared by the DA reaction of the corresponding 1,4

Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha,
• Ongolu Ravikumar and
• Jadab Majhi

Beilstein J. Org. Chem. 2015, 11, 1503–1508, doi:10.3762/bjoc.11.163

• -rearrangement metathesis as key steps. Here, we used a simple starting material such as dicyclopentadiene. Keywords: allylation; Beckmann rearrangement; lactams; oximes; ring-rearrangement metathesis; Introduction The Beckmann rearrangement (BR), a well-known protocol for the conversion of ketoxime to an

• target molecule 1 is shown in Figure 1. RRM of the tricyclic allylated compound 2 can deliver the target lactam 1. The key synthon 2 can be derived by allylation of lactam 3, which in turn can be prepared via BR starting with the known enone 4 [25][26][27], derived from dicyclopentadiene (5) [28][29][30

• lactams 9a and 9b were obtained in 48% yield (9a:9b = 2:1) the ratio of oximes 9a and 9b was calculated based on 1H NMR spectral data (Scheme 3). Having prepared the lactams 9a and 9b, the allylation reaction was attempted with the lactam mixture in the presence of NaH/allyl bromide in dry DMF to generate

Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• alkenylated sulfone derivatives. In this regard, Bloch and co-workers reported a useful preparation of monoallylated sulfone 8a [34]. To this end, we carried out the allylation of sulfone 6 with allyl bromide (1.2 equiv) and n-BuLi (2.7 equiv) at −75 °C to rt. The monoallylated sulfone 8a was obtained in 22

• supported by HRMS data. In addition, the structure and stereochemistry of the allyl groups present in compound 2a have been confirmed by single-crystal X-ray diffraction studies and this data clearly indicated that the allylation had occurred at α-position of the sulfone moiety and the two allyl groups are

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• -closing metathesis (RCM) are considered as viable options. The retrosynthetic analysis to the target bis-spiro-cage compound 7 is shown in Figure 2. The target compound 7 could be obtained from O-allylation of the Grignard addition product 11 followed by the two-fold RCM sequence. The required cage dione

• Grignard reagent attacks the other carbonyl group in a transannular fashion to generate hemiketal derivatives 12 and 13. Later, the diallyldiol 11 was subjected to an O-allylation sequence under NaH/allyl bromide conditions in DMF to deliver the desired tetraallyl compound 15 (53%) along with the triallyl

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• , reduction with LiAlH4, reductive amination and allylation that afforded the indole derivatives 63 (18%) and N-Boc protected compound 68 (23%). The reaction of 63 with Pd(OAc)2 (25 mol %) and tri(o-tolyl)phosphine (55 mol %) at reflux gave 9-endo-64a (24%) and 8-exo-65b (21%). However, the compound 68 under

• –Miyaura coupling: Bodwell and Li [127] have reported the synthesis of the cyclophane 130 involving hydroboration and the Suzuki–Miyaura (SM) coupling [128][129][130][131][132][133][134][135] as key steps. 1,3-Diallylindole (127) was first synthesized in two steps from indole (123) by successive allylation

• at the 3 position to give 126 (66%) and later, N-allylation was carried out to afford the diallylindole 127 (69%, Scheme 18). A three-step (123→124→125→127) sequence was found to give a higher yield of the 1,3-diallylindole (127). Iodination of 123 gave the 3-iodoindole (124) quantitatively, which on