The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

• -pot two-step procedure, combining the GBB-3CR and an acid-assisted deprotection reaction, to get a library of imidazo[2,1-f][1,2,4]triazin-4(3H)-ones 46, characterized by a flat heterocyclic ring system displaying the essential triad. Guanine derivatives are typically synthesized through a sequential

The Ugi4CR as effective tool to access promising anticancer isatin-based α-acetamide carboxamide oxindole hybrids

• Carolina S. Marques,
• Aday González-Bakker and
• José M. Padrón

Beilstein J. Org. Chem. 2024, 20, 1213–1220, doi:10.3762/bjoc.20.104

• -acetamide carboxamide isatin hybrids 8 easy accessed via deprotection reaction on the Ugi-adducts 5 and 7. TFA: trifluoroacetic acid. Supporting Information Supporting Information File 56: Experimental procedures, analytical data, NMR spectra and biological assays. Funding C. S. M. thanks the Norma

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• gave the corresponding epoxide 51 in low enantioselectivity and only 44% yield. The subsequent deprotection reaction led to compound 1 in 86% yield (Scheme 9). Besides the low enantioselectivity, the authors observed that the optical rotation value of the synthesized compound ([α]D +36.9, c 0.55, CHCl3

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• sequence including one deprotection reaction. One functional unit is α-lipoic acid (ALA) for binding the dye to gold surfaces. It was introduced to the DAT scaffold by an amidation reaction. The other functional unit is a para-(trifluoromethyl)benzyl group for facile detection of the surface-bound material

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• decided to go for anhydrous deprotection reaction, and in doing so, keeping the dialdehyde part untouched. Accordingly, hydrogen bromide was employed as a deprotection agent, as previously used by Borisenko et al. [23], to finally achieve the desired product 6 but in a very poor yield (5%). A second

Enhanced single-isomer separation and pseudoenantiomer resolution of new primary rim heterobifunctionalized α-cyclodextrin derivatives

• Iveta Tichá,
• Gábor Benkovics,
• Milo Malanga and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2018, 14, 2829–2837, doi:10.3762/bjoc.14.261

• practically no regioselectivity was observed. On the other hand, the dibromo-α-CD derivative was also prepared using a four-step indirect method involving DIBAL-H deprotection (reaction 4, Scheme 2) [10][30]. This method generated the AD regioisomer exclusively without AB or AC regioisomers as byproducts

An amine protecting group deprotectable under nearly neutral oxidative conditions

• Shahien Shahsavari,
• Chase McNamara,
• Mark Sylvester,
• Emily Bromley,
• Savannah Joslin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2018, 14, 1750–1757, doi:10.3762/bjoc.14.149

• the starting material insoluble and prevented deprotonation of H-2 in the oxidized 1,3-dithiane function. The problem was solved by using a solvent mixture of methanol and water. It is important to note that carrying out the deprotection reaction in one pot by performing the oxidation under basic

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• difficulties of the deprotection reaction in the presence of the labile seleno aglycon, the strategy was changed and the seleno moiety was introduced after methylation of fucose in position 2. As in our previous synthesis of 2-O-methylated fucoside [28], allyl alcohol was glycosylated with L-fucose (4) in a

Synthesis of pyrrolo[2,1-f][1,2,4]triazin-4(3H)-ones: Rearrangement of pyrrolo[1,2-d][1,3,4]oxadiazines and regioselective intramolecular cyclization of 1,2-biscarbamoyl-substituted 1H-pyrroles

• Kkonnip Son and
• Seong Jun Park

Beilstein J. Org. Chem. 2016, 12, 1780–1787, doi:10.3762/bjoc.12.168

• the reported rearrangement reaction, the desired product 12a’ was not accessed (approach B, Scheme 1). For the procedure using silica-gel column chromatography to afford triazinone 12a’ from the free amine-containing oxadiazine 11a’ [10], compound 11a’ was not present after the boc-deprotection

• reaction because of its instability in the acidic conditions. Based on the literature and the attempts reported herein, it should be highlighted that limitations exist for the preparation of the desired compounds 12. Due to these difficulties, we have investigated the synthesis of pyrrolotriazinones 12 by

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• a deprotection reaction in a single portion. In contrast, CsOH·H2O is a highly hygroscopic solid which must typically be added dropwise as a solution in (a minimum of) methanol, in which it has low solubility. This dropwise addition is important to minimise deprotection of the tosyl group of MPTTFs

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• conditions and can be carried on to 100% conversion. Similar results were found with diethyl 2-(4-methoxy-1-naphthyl)-2-oxoethyl phosphate (14b), although it was significantly less efficient compared with 14a. A key step in the deprotection reaction in aq MeOH is considered to be a Favorskii rearrangement of

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• ), TBS (tert-butyldimethylsilyl), MOM (methoxymethyl) and THP (tetrahydropyranyl) groups led to the corresponding bromophenols via a Tandem bromination/deprotection reaction (Table 2, entries 1–8, 12, 13, and 15), among which the cases with substituents at para- and ortho-position afforded 2- and 4

Synthesis of enantiopure sugar-decorated six-armed triptycene derivatives

• Paola Bonaccorsi,
• Maria Luisa Di Gioia,
• Antonella Leggio,
• Lucio Minuti,
• Teresa Papalia,
• Carlo Siciliano,
• Andrea Temperini and
• Anna Barattucci

Beilstein J. Org. Chem. 2013, 9, 2410–2416, doi:10.3762/bjoc.9.278

• -acetylated D-glucose substituted triptycene derivative 8 to a deprotection reaction, following a literature procedure [22]. After 36 h at rt and a number of washings with MeOH to eliminate acetamide, the sugar-decorated triptycene 10 was obtained from compound 8 in almost quantitative yield. The same

Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

• Han Wang,
• Kun Wen,
• Nurbiya Nurahmat,
• Yan Shao,
• He Zhang,
• Chao Wei,
• Ya Li,
• Yongjia Shen and
• Zhihua Sun

Beilstein J. Org. Chem. 2012, 8, 744–748, doi:10.3762/bjoc.8.84

• due to the added protection and deprotection reaction steps. Direct chlorination of unprotected aniline is possible by using sulfonyl chloride [1], chlorine [2][3] or N-chlorosuccinimide [4]. However, from an environmental-impact point of view, probably the best chlorination protocol was the one

Synthesis of oleophilic electron-rich phenylhydrazines

• Aleksandra Jankowiak and
• Piotr Kaszyński

Beilstein J. Org. Chem. 2012, 8, 275–282, doi:10.3762/bjoc.8.29

• arylhydrazine 1 in purities typically >90% as a viscous, yellow to orange oil that darkened upon standing. The quantitative analysis of the deprotection reaction was conducted with 0.2 mmol of 2 as described above. The yield of the hydrazines was established by adding known quantities of 1,4-dimethoxybenzene

A rapid and efficient synthetic route to terminal arylacetylenes by tetrabutylammonium hydroxide- and methanol-catalyzed cleavage of 4-aryl-2-methyl-3-butyn-2-ols

• Jie Li and
• Pengcheng Huang

Beilstein J. Org. Chem. 2011, 7, 426–431, doi:10.3762/bjoc.7.55

• reaction time under much milder conditions. Keywords: 4-aryl-2-methyl-3-butyn-2-ol; deprotection reaction; 2-methyl-3-butyn-2-ol; terminal alkynes; tetrabutylammonium hydroxide; Introduction Terminal arylacetylenes are key precursors for the construction of conjugated oligo- or polyarylacetylenes, which

• purified by chromatography because of the very different chromatographic polarities between the products and the aryl halides [13][14][15][16][17][18][19][20][21][22]. Nevertheless, the existing methods for the deprotection reaction (cleavage of 4-aryl-2-methyl-3-butyn-2-ols by removal of 2-hydroxypropyl

• mild conditions. This deprotection reaction is remarkably facile (5–30 min, 55–75 °C) in comparison to the existing methods (usually several hours, >110 °C) [13][14][15][16][17][18][19][20][21][22] and gives the terminal arylacetylene products in good to excellent yields (up to 98%). Results and

En route to photoaffinity labeling of the bacterial lectin FimH

• Thisbe K. Lindhorst,
• Michaela Märten,
• Andreas Fuchs and
• Stefan D. Knight

Beilstein J. Org. Chem. 2010, 6, 810–822, doi:10.3762/bjoc.6.91

• , 0.36 mmol) was dissolved in 80% aq TFA (5 mL) and stirred at RT for 60 min to cleave the tert-butyl ester. When the deprotection reaction was complete (TLC control in ethyl acetate:MeOH:H2O = 6:2:1) the solvent was removed in vacuo and the residue suspended in MeOH, filtered and the filtrate

• tert-butyl ester. When the deprotection reaction was complete (TLC control in ethyl acetate:MeOH:H2O = 6:2:1) the solvent was removed in vacuo and the residue suspended in MeOH, filtered and the filtrate concentrated under reduced pressure. The resulting crude product was combined with HATU (98.1 mg

The enantiospecific synthesis of (+)-monomorine I using a 5-endo- trig cyclisation strategy

• Malcolm B. Berry,
• Donald Craig,
• Philip S. Jones and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2007, 3, No. 39, doi:10.1186/1860-5397-3-39

• achieved. Whilst the tosyl-based methodology permitted the synthesis of a range of simple, non-functionalised pyrrolidines 5 (X = NH), the harsh nature of the deprotection reaction, treatment with hydrobromic acid and phenol in acetic acid at reflux, led to the destruction of the the terminal alkene