Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• precursor 49 in situ through a Pd/Cu mediated coupling reaction between (trimethylsilyl)acetylene (TMSA) with an aryl iodide, followed by a desilylation reaction. The subsequent addition of the third partner, an o-iodoanilide derivative, allowed a Pd/Cu tandem C–C/C–N-bond-forming reaction. The main

• . Synthesis of indoles through a sequential C–C coupling/desilylation–coupling/cyclization reaction. Synthesis of indoles by a site selective Pd/C catalyzed cross-coupling approach. Synthesis of isoindolin-1-one derivatives through a sequential Sonogashira coupling/carbonylation/hydroamination reaction

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• provide dihydropyridine 6. Elimination of trimethylsilanol and subsequent O-desilylation affords the 4-hydroxypyridine 7 (Scheme 1). The desired β-ketoenamides 4 are either accessible by acylation of enaminoketones or by a multicomponent reaction of lithiated alkoxyallenes, nitriles and carboxylic acids

• , whereas the pyridinol tautomer is favored when a hydrogen bond-donor is present. Compound 37 exists exclusively as pyridone tautomer, but after desilylation the resulting product, with a free hydroxy group in the side chain, strongly prefers the pyridinol tautomer. It seems reasonable to assume that the

• 22 could be O-methylated in good yield with methyl iodide in THF, the same conditions converted 30 into 55 in a disappointing 30% yield. Desilylation of 53 and 55 with HF in pyridine gave the desired deprotected pyridine derivatives 54 and 56 in high yields. This type of enantiopure hydroxymethyl

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• structure of 28a. Catalysts 34, 35 and 36. 1H NMR spectra of the separated diastereoisomers of the substrates for catalysis 28 (left) and of the products 37 (right, the small signals are due to the deprotected compounds 38). Structure of the desilylation product 38. Mechanism of the furan–yne reaction

Gold-catalyzed alkylation of silyl enol ethers with ortho-alkynylbenzoic acid esters

• Haruo Aikawa,
• Tetsuro Kaneko,
• Naoki Asao and
• Yoshinori Yamamoto

Beilstein J. Org. Chem. 2011, 7, 648–652, doi:10.3762/bjoc.7.76

• formation of 3a. It is well known that concerted pericyclic ene-type reaction of silyl enol ethers with electrophiles, such as aldehydes or ketones, gives functionalized silyl enol ethers without desilylation [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. To the best of our knowledge, however

Gold-catalyzed regioselective oxidation of terminal allenes: formation of α-methanesulfonyloxy methyl ketones

• Yingdong Luo,
• Guozhu Zhang,
• Erik S. Hwang,
• Thomas A. Wilcoxon and
• Liming Zhang

Beilstein J. Org. Chem. 2011, 7, 596–600, doi:10.3762/bjoc.7.69

• example, allenes derived by replacing the acetoxy group of 1b with a free OH or an OTBS group did not lead to the desired products. Presumably, the nucleophilic OH group in the substrate, or one generated via acidic desilylation, interfered with the reaction. This reasoning was supported by the isolation

A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• reaction time was intentionally extended to ensure complete desilylation. A second mechanistic alternative, path b, cannot be ruled out at this time. Path b involves gold-activation of the alkyne followed by 5-exo-dig nucleophilic attack of the acetal oxygen. Methanolysis of the acetal and spirocyclization

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• with iodine [7]. 1-Ethynyl-2-iodo-benzene (15) [30] was prepared in quantitative yield by desilylation of 1-iodo-2-[2-(trimethylsilyl)ethynyl]benzene with sodium hydroxide in methanol. 1-Ethynyl-2-(methoxymethyl)benzene (4b) [31] and dimethyl (1-diazo-2-oxopropyl)phosphonate [32] were prepared

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• remaining hydroxyl groups afforded the glycoside 13, which was desilylated with HF·pyridine complex to yield 14. This chemoselective transformation uses conditions that are similar to those reported by Tam et al. [23], and result in desilylation in a significantly shorter period than that previously

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• thioglycoside 4 [14] yielded the 6-O-silylated compound 5 (92%), benzylation of which gave donor 6 (85%). A benzyl group in the 4-position was preferred to an ester group to avoid the risk of acyl migration during subsequent reactions; desilylation, glycosidation and phosphorylation. 3II,4II-Diols of lactose

Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs

• Dhananjaya Sahoo,
• Susanne Thiele,
• Miriam Schulte,
• Navid Ramezanian and
• Adelheid Godt

Beilstein J. Org. Chem. 2010, 6, No. 57, doi:10.3762/bjoc.6.57

• synthetic routes have emerged: The repeating unit by repeating unit approach (Scheme 1a) with desilylation and coupling of the (functionalized) arylethyne with 1-iodo-4-(2-trimethylsilylethynyl)benzene as the two repeating steps [6][9][20][21][22][23][24]. The oligomer grows slowly repeating unit by

• -trimethylsilylethynyl)benzene is the parent compound. Desilylation and exchange of the triazenyl substituent for an iodo substituent are the two divergent steps followed by the alkynyl–aryl coupling, the convergent step. The dialkyltriazenyl group decomposes during chromatography on silica gel [28]. The divergent

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• hydrogenation, desilylation and removal of the butane diacetal group finished the total synthesis of 134. The spectroscopic data for synthetic 134 (1H NMR, 13C NMR, IR, MS, mp and specific rotation) were in excellent agreement with those reported for naturally occurring muricatetrocin C (134). In 2002, the full

• . Oxidative release of 160 followed by Swern oxidation and Takai reaction provided the terminal vinyl iodide 161. Final Pd0-catalyzed coupling of alkyne 157 with vinyl iodide 161 gave the enediyne 162, which underwent selective hydrogenation and desilylation to give (+)-parviflorin (153). In 1997, Trost’s

Synthesis of chiral cyclohexanes and carbasugars by 6-exo-dig radical cyclisation reactions

• Rajeev K. Shrivastava,
• Elise Maudru,
• Gurdial Singh,
• Richard H. Wightman and
• Keith M. Morgan

Beilstein J. Org. Chem. 2008, 4, No. 43, doi:10.3762/bjoc.4.43

• juncture we were able to separate the diastereoisomers, 3a (anti) and 3b (syn), by flash column chromatography on silica gel. Alternatively the syn isomer 3b could be prepared almost exclusively using D-ribonolactone as the starting material [23]. Desilylation of 3a was effective with TBAF in THF and

• 96% and 91% yields, respectively. These compounds were identical to those obtained from 2c after the diastereoisomers had been subjected to protection as MOM ethers on treatment with MOM chloride to give 5a and 5b followed by desilylation, the anti:syn ratio being 2.3:1. The syn-product was

Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• unsuccessful, apparently because the silyl ether failed to survive the reaction conditions. Inelegant though it was, we were forced at this stage to change protecting groups on the alcohol. Fortunately, the drop in yield was not too serious when desilylation of 34 with aqueous hydrofluoric acid to give the

Investigation of acetyl migrations in furanosides

• O. P. Chevallier and
• M. E. Migaud

Beilstein J. Org. Chem. 2006, 2, No. 14, doi:10.1186/1860-5397-2-14

• O. P. Chevallier M. E. Migaud School of Chemistry and Chemical Engineering, Queen's University, David Keir Building, Stranmillis Road, Belfast, BT9 5AG, Northern Ireland, UK 10.1186/1860-5397-2-14 Abstract Standard reaction conditions for the desilylation of acetylated furanoside (riboside

• ribosides, acyl migration could be prevented when desilylation was catalysed by cerium ammonium nitrate. Introduction Over the years, a number of methods aimed at achieving chemoselective acylation of carbohydrates have been developed.[1][2][3] In addition to the challenges encountered in the selective

• experiments were sufficiently clear to allow accurate compound identification. No isomerisation was detected for any of the isolated compounds when stored in an organic solvent such as hexane, ethyl acetate or CDCl3 for up to 12 hrs. The chemical shifts of the 1H- and 13C-NMR of the desilylation products for

The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

• Ishmael B. Masesane,
• Andrei S. Batsanov,
• Judith A. K. Howard,
• Raju Mondal and
• Patrick G. Steel

Beilstein J. Org. Chem. 2006, 2, No. 9, doi:10.1186/1860-5397-2-9

• failed. Fortunately, use of LiHMDS was successful albeit accompanied by the unexpected loss of Boc group. Similar strategies using either the free diol or the corresponding acetonide were not successful leading to extensive decomposition. Following TBAF promoted desilylation, peracylation and reduction

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• silylketenes with reactive ylides involves deprotonation by the basic reagent to generate ynolate anions. Clearly, since such a pathway cannot operate with the substituted ketenes used here other mechanisms are at play, which may include nucleophilic desilylation or ketene oligomerisation initiated by