Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• desilylation was either subjected to a Sonogashira coupling with 9 to give 4 or to an oxidative Hay coupling to give 5 – using recently developed conditions where 4 Å molecular sieves were added to the reaction mixture to remove water [17]. Compounds 6 and 7 were prepared by treating 9 with either the trans

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• benzylamine yielding amine 10, which was subsequently Boc-protected, then reacted with trimethylsilylacetylene in a Sonogashira cross-coupling followed by desilylation. Finally, the porphyrin cores 1 and 2 were combined with axle precursor 8 in another two and four-fold Sonogashira cross-coupling reaction

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• - and diasterioselective fashion and tolerate a range of functionalities. Experimental General procedure for the cobalt-catalysed 1,4-hydrovinylation of aryl-substituted buta-1,3-dienes with allyloxytrimethylsilane and subsequent desilylation with TBAF Cobalt dibromo(1,3-bis(diphenylphosphino)ethane) (5

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• desilylation (10). The subsequent CuAAC coupling between 9 and 10 turned out to be difficult. Whereas the reaction failed under standard conditions [18] we succeeded after numerous variations of the reaction conditions by applying the Cu/C catalyst [19] in a solvent mixture of DCM and MeOH in the presence of

NAA-modified DNA oligonucleotides with zwitterionic backbones: stereoselective synthesis of A–T phosphoramidite building blocks

• Boris Schmidtgall,
• Claudia Höbartner and
• Christian Ducho

Beilstein J. Org. Chem. 2015, 11, 50–60, doi:10.3762/bjoc.11.8

• with methanol), thus providing 3'-O-TBDMS-protected derivatives 15 and 16 in yields of 59% and 66%, respectively. This method turned out to be advantageous compared to 5'-O-desilylation mediated by TFA, which had provided satisfying results in the case of the corresponding uridine derivatives [48]. The

• %, respectively. For the subsequent desilylation reaction, several reaction conditions were tested, among them acidic silyl ether cleavage with hydrochloric acid in methanol or treatment with triethylamine trihydrofluoride (3HF•NEt3). However, the only successful method was the conversion of both epimers of 26

A carbohydrate approach for the formal total synthesis of (−)-aspergillide C

• Pabbaraja Srihari,
• Namballa Hari Krishna,
• Ydhyam Sridhar and
• Ahmed Kamal

Beilstein J. Org. Chem. 2014, 10, 3122–3126, doi:10.3762/bjoc.10.329

• deprotecting the acetyl groups (without affecting the benzoate functionality) by employing acetyl chloride in anhydrous methanol to afford diol 13 [33]. A two-fold silylation and selective mono desilylation afforded primary alcohol 14 which was converted to its corresponding nitrile via the triflate. The

Redox active dendronized polystyrenes equipped with peripheral triarylamines

• Toshiki Nokami,
• Naoki Musya,
• Tatsuya Morofuji,
• Keiji Takeda,
• Masahiro Takumi,
• Akihiro Shimizu and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2014, 10, 3097–3103, doi:10.3762/bjoc.10.326

• consistent with the observation that dendrimer 10 prepared by desilylation of 5 followed by amination (see Supporting Information File 1 for preparative details) showed two reversible waves occurring at similar potentials (E1/2 = 0.81 and 1.10 V vs SCE) (Figure 5, blue line). A film of dendronized

Galactan synthesis in a single step via oligomerization of monosaccharides

• Marius Dräger and
• Amit Basu

Beilstein J. Org. Chem. 2014, 10, 2658–2663, doi:10.3762/bjoc.10.279

• observations suggest that desilylation is most likely the result of transient Brønsted acid formation during the reaction and not due to fluoride ion generation. In an attempt to tune silyl ether deprotection rates and promote formation of longer oligomers, we examined the glycosylation of a bulkier TBDPS

Synthesis and immunological evaluation of protein conjugates of Neisseria meningitidis X capsular polysaccharide fragments

• Laura Morelli,
• Damiano Cancogni,
• Marta Tontini,
• Alberto Nilo,
• Sara Filippini,
• Paolo Costantino,
• Maria Rosaria Romano,
• Francesco Berti,
• Roberto Adamo and
• Luigi Lay

Beilstein J. Org. Chem. 2014, 10, 2367–2376, doi:10.3762/bjoc.10.247

• ). On the other hand, the same reaction carried out on protected glycosyl phosphosaccharides afforded the corresponding acetamides in 25–35% yield [25]. Interestingly, when compound 5 was subjected to 1-O-desilylation with tetrabutylammonium fluoride in THF at –40 °C, we obtained exclusively the α

• for the high selectivity observed in the formation of compound 6 and, consequently, for the attainment of the pure α-H-phosphonate 7. Indeed, the desilylation of the 2-azido counterpart of intermediate 5 provided a mixture of anomers. On the other hand, the same reaction carried out on a 2-acetamido

Solution phase synthesis of short oligoribonucleotides on a precipitative tetrapodal support

• Alejandro Gimenez Molina,
• Amit M. Jabgunde,
• Pasi Virta and
• Harri Lönnberg

Beilstein J. Org. Chem. 2014, 10, 2279–2285, doi:10.3762/bjoc.10.237

• -catalyzed acetalization with 2-methoxypropene in THF. The subsequent 3'-O desilylation of the fully protected nucleosides (3a–d) then required careful adjustment of conditions. Desilylation with NH4F in MeOH turned out to be successful in the sense that the 2'-O and 5'-O protecting groups remained intact

Synthesis of phosphoramidites of isoGNA, an isomer of glycerol nucleic acid

• Keunsoo Kim,
• Venkateshwarlu Punna,
• Phaneendrasai Karri and
• Ramanarayanan Krishnamurthy

Beilstein J. Org. Chem. 2014, 10, 2131–2138, doi:10.3762/bjoc.10.220

• by vanadium trichloride gave the desired product 9 cleanly in large-scale reactions [30]. The desilylation of intermediates 11, 20 and 26 was effected by the treatment of 1 M TBAF in THF at 0 °C to room temperature. In the case of guanine derivative 23, we observed that the use of the

Expedient synthesis of 1,6-anhydro-α-D-galactofuranose, a useful intermediate for glycobiological tools

• Luciana Baldoni and
• Carla Marino

Beilstein J. Org. Chem. 2014, 10, 1651–1656, doi:10.3762/bjoc.10.172

• three-step procedure for the synthesis of 1,6-anhydro-α-D-galactofuranose is described. The key step involves the formation of the galactofuranosyl iodide by treatment of per-O-TBS-D-Galf with TMSI, the selective 6-O-desilylation by an excess of TMSI, and the simultaneous nucleophilic attack of the 6

• , but in a lower yield due to the O-desilylation of another hydroxy group. The addition of BF3·OEt2 to recently formed 10 resulted in the formation of compound 12. Several factors favor the formation of the bicyclic system of compound 12, such as the galactose structure itself, the presence of a good

• conditions and compound 12 was obtained instead (Figure 3). The O-desilylation of 12 was performed by treatment with n-Bu4F as previously optimized [32][33][34], affording compound 2 in almost quantitative yield (Scheme 3). Conclusion In conclusion, we have described a new and concise procedure for the

Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

• Bernd Schmidt and
• Sylvia Hauke

Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102

• -amicetose 7 [35]. To avoid the last step of the sequence, we envisaged a cross metathesis with acroleine, rather than methyl acrylate, to give enal 8 which should undergo spontaneous lactol formation after hydrogenation and desilylation. However, compared to cross metathesis reactions with methyl acrylate

• dealkoxylation of acetals [65] and for desilylation reactions of silyl ethers [66]. With in situ generated Pd/C (obtained from Pd(OAc)2 and charcoal according to Felpin’s protocol) [67] an improved selectivity was observed as the cleavage of the silyl groups could be suppressed. However, reductive dealkoxylation

• 83% combined yield (Table 3, entry 3). For the deprotection of 11 and 12 a desilylation initiated by TBAF, followed by acidic hydrolysis was investigated first. With isolated acetal 11, these conditions induced a scrambling of the benzoate and led to a mixture of the desired pyranose 16 and the

Asymmetric total synthesis of a putative sex pheromone component from the parasitoid wasp Trichogramma turkestanica

• Danny Geerdink,
• Jeffrey Buter,
• Teris A. van Beek and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2014, 10, 761–766, doi:10.3762/bjoc.10.71

•  2) [24]. The use of 1.2 equiv of BF3·Et2O led to 9 in 84% isolated yield. Reduction of 9 with freshly prepared Raney nickel and subsequent desilylation afforded 10 over two steps in 73% yield. To introduce the desired E,E-diene present in 2 and 1, we realized that the procedure reported by

• components of Trichogramma turkestanica. Application of the iterative conjugate addition protocol for the preparation of 8. Deoxygenation and desilylation of 8. Vinylogous Horner–Wadsworth–Emmons olefination. Synthesis of α,β-unsaturated ester 15 using a Wittig reaction. Completion of the synthesis of the

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• . For example, Kubo and coworkers [47] showed that photoreactions of N-methyl-1,2- and 2,3-naphthalimides 8 and 12 with allylsilane 9 in MeCN can produce allylation products [48][49][50][51][52] that arise by a well-known sequence involving intermolecular SET, radical cation desilylation and radical

• delocalization arising by the orbital overlap, lowers the σC-Si bond dissociation energy and makes the silicon center more electropositive. Consequently, short-lived α-silyl cation radicals typically undergo fast, silophile-promoted desilylation to form the carbon centered free radicals 19 (Scheme 4). Based on

• the low oxidation potentials and known reactivity profile of cation radicals arising from α-trialkylsilyl substituted n-electron donors, it is feasible to design substrates that undergo sequential SET-desilylation processes to produce radicals or biradical intermediates in a highly regioselective and

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• bidentate chelation (Scheme 36). The substrate is bound anti to the bulky amino acid substituent (R) and reacts with the siloxyfuran via endo-type addition. Intramolecular silyl transfer, iPrOH mediated desilylation of the amide terminus, and protonation of the N–Ag bond delivers the final product and the

Deoxygenative gem-difluoroolefination of carbonyl compounds with (chlorodifluoromethyl)trimethylsilane and triphenylphosphine

• Fei Wang,
• Lingchun Li,
• Chuanfa Ni and
• Jinbo Hu

Beilstein J. Org. Chem. 2014, 10, 344–351, doi:10.3762/bjoc.10.32

• occurs to give TMSCl with regeneration of PPh3; meanwhile, the trapping of :CF2 by PPh3 gives the ylide. In Path B, a phosphonium salt 10, which is formed via a single-electron transfer (SET) mechanism, undergoes a chloride ion-promoted desilylation reaction to afford Ph3P=CF2 [42][43]. However, we could

Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog

• Werner Telle,
• Gerhard Kelter,
• Heinz-Herbert Fiebig,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2014, 10, 316–322, doi:10.3762/bjoc.10.29

• both coupling partners 12 and 13 completely, by repeated evaporation of DCM solutions. Finally, a coupling yield of 68% was reached following the DEPC protocol. Desilylation (TBAF in THF/H2O) afforded 1 (HRESIMS found 755.49257, calcd. for C40H68NaN4O8 755.49294) in 12% yield after 10 steps from

• afforded building block 26. Coupling with Boc-protected dolaproine (27, DCC/DMAP/CSA) yielded ester 28 as a mixture of two diastereomers. After deprotection of the pyrrolidine, coupling with tripeptide 12 afforded O-silylated diazirinyl-substituted malevamide D (29, 68%). Desilylation (TBAF, THF/H2O 19:1

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• alcohol 18 and Mitsunobu reaction installed the required stereochemistry at C14. The free C14 hydroxy group was masked with protecting groups (MOM and TIPS) of different size and chemical nature to examine the face-selectivity of the [3,3]-sigmatropic rearrangement. After selective desilylation, alcohols

• aqueous CH2Cl2 to release triol 36, which was masked with different protecting groups (MOM, TBS, Piv). After desilylation, the liberated alcohols 40, 41 and 42 could be esterified with various cyclic and acyclic model A rings to give the targeted rearrangement precursors A (Scheme 6, Table 2). The

• , desilylation, oxidation and esterification (Scheme 14). Attempts to rearrange 93 under the optimized conditions were again unsuccessful. As expected, elimination of the OMOM group during the reaction was not detected due to the unfavoured orientation of the hydrogen and the leaving group. Subsequent acidic

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

• diterpene 5-epi-vibsanin E (115), from the plant Viburnum awabuki (see Scheme 14) [104]. Starting from triene 108 cyclopropanation was achieved using vinyldiazo compound 101. The fomal [4 + 3]-cycloaddition proceeded through cis-divinylcyclopropane 109 to yield rearranged cycloheptadiene 110. Desilylation

• towards the total synthesis of salvileucalin B (292, see Scheme 35) isolated from the plant Salvia leucantha [213]. Starting from enantiopure trialkyne 282, desilylation was affected using TBAF, followed by ruthenium-catalyzed cycloisomerization [214] and cleavage of the chiral auxiliary to obtain

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

• obtained as the by-product (Scheme 15, Table 6) [249]. The desilylation of the initially formed silicon peroxide followed by cyclization of the hydroperoxide accompanied by the attack on the electrophilic center is another example of the use of the Isayama–Mukaiyama reaction for the synthesis of cyclic

• 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

• activated double bond or a carbon atom of a keto or ester group). The desilylation of tert-butyldimethylsilylperoxy ketones 131a,b with HF followed by cyclization and subsequent reaction with monomethylethylene glycol afforded dioxolanes 132a,b in 75 and 88% yield, respectively. The intermediate

Total synthesis of the endogenous inflammation resolving lipid resolvin D2 using a common lynchpin

• John Li,
• May May Leong,
• Alastair Stewart and
• Mark A. Rizzacasa

Beilstein J. Org. Chem. 2013, 9, 2762–2766, doi:10.3762/bjoc.9.310

• . Desilylation of 11 followed by hydrozirconation and iodination gave the vinyl iodide 4 and Sonogashira coupling between this compound and enyne 3 provided alkyne 18. Acetonide deprotection, partial reduction and ester hydrolysis then gave resolvin D2 (1). Keywords: catalysis; eicosanoid; natural product

• bis-TES ether 15 and partial reduction of the alkyne using P2-Ni as catalyst [30] afforded the alkene 16. Desilylation of the primary TES group in 16 and concomitant oxidation to aldehyde 5 was achieved under Swern conditions as reported by Spur [31]. Deprotonation of salt 6 with LiHMDS followed by

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

• the electron-deficient double bond, using polymethylhydrosiloxane (PMHS) [40] as a reducing agent and a BDP–Cu hydride catalyst. This variant of Stryker’s reagent [41] has more recently been described by Lipshutz et al. [42] and was found to furnish ketone 13 in 74% yield. Desilylation of 13 could be

• 19:1, it was converted to 26 via Mitsunobu inversion [55] with acetic acid as the nucleophile. The synthesis of stagonolide E commenced with the desilylation of 26 and Steglich esterification of the resulting allyl alcohol 27. One-flask reaction of 28 with catalyst B, followed by treatment with NaH

Towards stereochemical control: A short formal enantioselective total synthesis of pumiliotoxins 251D and 237A

• Jie Zhang,
• Hong-Kui Zhang and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2013, 9, 2358–2366, doi:10.3762/bjoc.9.271

• of (R)-3-(tert-butyldimethylsilyloxy)glutarimide 14. After O-desilylation and Dess–Martin oxidation, the resulting keto-lactam 10 was subjected to a highly trans-stereoselective addition of the methylmagnesium iodide to give carbinol 11 as sole diastereomer. An efficient ring closure procedure

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• ether should be removed by using hydrolysis and fluoride-mediated desilylation, respectively. It was assumed that the multiple carbopalladation/cyclization sequence should give access to the fourfold-annulated ring system 13 in a single step. However, we knew that the domino process works much better in

• more promising candidates. But none of these domino products 13b–13f provided better results in a Tamao–Fleming reaction. When oxidizing reaction conditions were applied to silane 13b, only desilylation of the cyclic silyl ether occurred. Interestingly, benzylsilane 13c afforded the globally