N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• (Scheme 13). The proposed mechanism for the reaction starts with the generation of the N-(propargyl)thioamide intermediates A through a thioacylation of N-propargylamine 47 with benzotriazolylthione 48. Then N-desilylation of A furnishes intermediate B which undergoes a base-promoted cyclization to give

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• 1,2,3-triazoles [50]. After the desilylation of syn-5 using potassium fluoride in methanol (Scheme 8) the resulting mono-substituted alkyne was subjected to an established protocol using benzyl azide, copper(I) iodide, triethylamine and TBTA [51] (for a recent review see [52]). The cycloaddition

• . Cross-coupling reaction of 1,2-oxazine anti-4d leading to 5-cyano-substituted 1,2-oxazine anti-25. Desilylation of 1,2-oxazine syn-5 and subsequent click reaction with benzyl azide leading to 5-(1,2,3-triazolyl)-substituted 1,2-oxazine syn-26. Hydrogenation of 1,2-oxazine syn-21 leading to γ-amino

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

• Michał Malik and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255

• ]. After desilylation followed by protection of the free hydroxy with a benzoyl group and deprotection of the isopropylidene moiety, diols 20 and 24 were obtained. With α,β-unsaturated ketones 17 and 18 and two enantiomeric, optically pure aldehydes (R)- and (S)-10 in hand, we started to study the 1,4

Synthesis of medronic acid monoesters and their purification by high-performance countercurrent chromatography or by hydroxyapatite

• Elina Puljula,
• Jouko Vepsäläinen and
• Petri A. Turhanen

Beilstein J. Org. Chem. 2016, 12, 2145–2149, doi:10.3762/bjoc.12.204

• before the purification. Conclusion Mixed tetraesters of medronic acid were prepared with relatively high yields (60–78%) and used as starting material for the synthesis of monoesters of medronic acid. A series of medronic acid monoesters were synthesized by using a silylation and desilylation procedure

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• , decreasing in the series t-BuMe2Si > Et3Si > Me3Si. It has been shown that Ir-hydride complexes that are formed as intermediates during hydrogenation are strong Brønsted acids [32], which can cause cleavage of trimethylsilyl ethers under hydrogenation conditions [33]. So partial desilylation liberating a

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• length via stereospecific nucleophilic displacement of the chiral auxiliary with complete inversion of configuration at the sulfur center [46][47]. Sulfoxide 3 is incorporated into the catalyst via a [3 + 2] oxidative cycloaddition with allylruthenium complex 4. Desilylation of cationic complex 5, ion

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

• -dimethylimidazolone 4 (R1 = R2 = Me) in the presence of catalyst C1 afforded, after desilylation, the Michael adduct 30 in good yield (74%) but in moderate enantioselectivity (−84%). Improved selectivity (91%) was observed using C2 in the reaction with 4 (R 1= R2 = Me) and even better enantioselectivity was obtained

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• give 61. A sequence of desilylation and oxidation furnished the acid 62. Peptide coupling with amine 63 and acidic deprotection then afforded the desired aldehyde 64, which already contained the muraymycin linker unit (Scheme 8) [107]. Together with the uridine core structure 50 and the urea dipeptide

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• included the second indole moiety of raputindole A (1). Boc protection of 6-iodoindole (2) [35], Sonogashira reaction of 3 with TMS-acetylene, and desilylation gave the N-protected alkynylindole 4 in excellent yield (Scheme 2). Boc-iodoindole 3 was also the precursor of the coupling partner, ketone 6

• Chancellor and coworkers [42], gave nitrophenol 11 in a reasonable yield (45%). The Batcho–Leimgruber protocol failed for nitrophenol 11 [43]. However, after O-benzylation of 11 to 12, Boc-indole 15 was obtained in the very good yield of 91%. Coupling with TMS-acetylene was followed by desilylation to obtain

• PMB group, because the oxidation potential of DMB ethers is lower and the cleavage was expected to be more facile [45]. Indole synthesis from DMB-protected 13 and subsequent Boc protection afforded 16 (58%). Alkynylation and desilylation of 16 to 19 and coupling of 19 with ketone 6 proceeded smoothly

Hydroquinone–pyrrole dyads with varied linkers

• Hao Huang,
• Christoffer Karlsson,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 89–96, doi:10.3762/bjoc.12.10

• parameters was investigated, involving the selection of base and solvent. However, none of the attempted conditions gave the desired product. Instead, desilylation of 3-iodo-1-(triisopropylsilyl)-1H-pyrrole was observed during the reaction, and some of the dimethoxystyrene could be recovered (for details

• expected to have different electronic properties. After desilylation, compound 3c was obtained in a combined total yield of 35% (sum of cis-3c and trans-3c) from the pyrrole-3-carbaldehyde. To obtain trans-4c selectively, a Wittig–Horner reaction was investigated, with dimethoxybenzyl bromide as starting

• 3-bromo-1-(triisopropylsilyl)-1H-pyrrole resulted in low yield (20%) and also homocoupling. Considering that desilylation of triisopropylsilyl protected pyrrole might occur at high temperature in DMF, an overnight reaction at room temperature was performed, resulting in a yield for 4d of 50%. In

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• alcohol was converted to the corresponding silyl ether. Next, alkylation of the metalated sulfone with allylic chloride 51 afforded alcohol 52 after desilylation. Subsequent desulfonylation with sodium amalgam and Jones oxidation of the primary alcohol furnished carboxylic acid 53. The corresponding

• product 63 in very good yield, however, as a mixture of lactol epimers (α/β ≈ 56:44). Silyl protection of the lactol and subsequent Tebbe olefination [42] of the ketone group installed the exocyclic double bond of the nine-membered carbocycle. Desilylation followed by oxidation with silver carbonate then

• acetylide to the carbonyl group of 69, followed by desilylation under basic conditions gave rise to (±)-ethynylcarbinol, which was separated by chiral HPLC. The desired diastereomer was then transformed to benzene sulfinate ester 70. A palladium-catalyzed [2,3]-sigmatropic rearrangement formed an isomeric

Synthesis of alpha-tetrasubstituted triazoles by copper-catalyzed silyl deprotection/azide cycloaddition

• Zachary L. Palchak,
• Paula T. Nguyen and
• Catharine H. Larsen

Beilstein J. Org. Chem. 2015, 11, 1425–1433, doi:10.3762/bjoc.11.154

• in CuAAC reactions, copper(II) triflate is known to form protic acid in solution, which could cause proto-desilylation [36], but this is not observed. A broader range of green alcohol solvents [37] were assessed in the presence of the most active catalyst, in situ reduced Cu(OTf)2. Isopropanol was

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

• 26, which was subsequently converted to the cyclophane 28 by a Mannich-type condensation reaction (40%) (Scheme 1). Michael addition: In 1999, Reißig and co-workers [85] have synthesized a functionalized cyclophane by a cascade reaction, which proceeds with desilylation, ring opening, proton transfer

• -diiodobenzene with an excess amount of triisopropylsilylbutadiyne (47) followed by complexation with Co2(CO)8 furnished a pale yellow diyne 48. Exchange of the ligand with bis(diphenylphosphino)methane (dppm) afforded a bridged complex which is stable to fluoride ions. Subsequent desilylation, followed by

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