The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• , it has to be noted that the trans-THF was not directly formed in an oxidative cyclization reaction but rather through a subsequent sequential solvolysis/hydride shift/intramolecular reduction cascade. Another total synthesis of cis-sylvaticin (40) has been published by Brown and co-workers in 2008

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• acetone (171). The Sn(OTf)2 and La(OTf)3-catalyzed reaction afforded neopentyl alcohol (173) in 62 and 70% yield, respectively [320]. The hydrogen peroxide promoted ring expansion for the synthesis of oxabicycles 176a–c was described for the first time in 1985 [321]. The reaction involved the solvolysis

• of homoallylic brosylates 174a–c or spiro cyclopropyl carbinols 175a–c in the THF/H2O2 system, resulting in the increase in the ring size by two atoms and the formation of hydroperoxy oxabicyclo derivatives 176a–c (Table 11). The mechanism of the solvolysis of 174 or 175 in the THF/H2O2 system

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• hydrolysis of the lipopolysaccharide isolated by the phenol–water extraction from the halotolerant soil bacteria Azospirillum halopraeferens type strain Au4. The polysaccharide was studied by sugar and methylation analyses, selective cleavages by Smith degradation and solvolysis with trifluoroacetic acid

• residue (~65%), are shown in italics. Keywords: Azospirillum halopraeferens; bacterial polysaccharide structure; lipopolysaccharide; O-specific polysaccharide; Smith degradation; triflic acid solvolysis; Introduction Rhizobacteria of the genus Azospirillum are isolated from a wide variety of

• oligosaccharide, selective solvolysis with CF3CO2H was employed. Recently, this method has been successfully used for the structure elucidation of the O-specific polysaccharides of Escherichia coli (e.g. [20]). The reagent was found to cleave selectively the glycosidic linkage of 6-deoxyhexoses (Rha, Fuc

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• solvolysis of syn- and anti-norborn-2-en-7-ylmethyl-X diastereomers (Is and Ia, Figure 6; X is a leaving group) both led to the same two products, but in different ratios, despite sharing a common intermediate (in different conformations; V, Figure 6) [59]. The major product generated from the solvolysis of

• Ia was the acetate of carbocation L, with a small amount of the acetate of carbocation G also observed. Solvolysis of Is also led to the acetate of carbocation L, but this time accompanied by a significant amount of the acetate of carbocation G. This difference in product distribution (whose

Amino-functionalized (meth)acryl polymers by use of a solvent-polarity sensitive protecting group (Br-t-BOC)

• Helmut Ritter,
• Monir Tabatabai and
• Markus Herrmann

Beilstein J. Org. Chem. 2016, 12, 245–252, doi:10.3762/bjoc.12.26

• -BOC)-aminoethyl (meth)acrylate) 6a,b bearing protected amino side groups. The subsequent solvolysis of the Br-t-BOC function led to the new polymers poly(2-aminoethyl (meth)acrylate) 8a,b with protonated free amino groups. The monomers and the resulting polymers were thoroughly characterized by 1H NMR

• . Carpino [8][9][10] and a first practical application in peptide synthesis [11] this protecting group was quasi forgotten. In the present work we report new Br-t-Boc-protected (meth)acrylic monomers and their polymerization through free radical polymerization. The kinetics of Br-t-BOC solvolysis of the

• deprotection for 3a,b, 6a,b and 7a,b are summarized in Table 1. As assumed above the molecular dispersed monomer shows the highest reactivity followed by the copolymer. The solvolysis of the protecting group in the homopolymer is relatively slow because of neighboring group formed retarding hydrogen bonds

Synthesis of multivalent carbohydrate mimetics with aminopolyol end groups and their evaluation as L-selectin inhibitors

• Joana Salta,
• Jens Dernedde and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2015, 11, 638–646, doi:10.3762/bjoc.11.72

• -up protocol for the very hydrophilic products. Acid-promoted solvolysis in the absence of water [31] was considered as good alternative that should have the advantage of generating side products that can easily be removed in vacuo, making further purification unnecessary. First attempts with acetyl

3α,5α-Cyclocholestan-6β-yl ethers as donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates

• Aneta M. Tomkiel,
• Adam Biedrzycki,
• Jolanta Płoszyńska,
• Dorota Naróg,
• Andrzej Sobkowiak and
• Jacek W. Morzycki

Beilstein J. Org. Chem. 2015, 11, 162–168, doi:10.3762/bjoc.11.16

• , finally, cholesteryl diphenylphosphate (5) was selected as the best cholesteryl donor [5]. Apart from these cholesterol derivatives, also simple alkyl or aryl ethers (6b–g) of 3α,5α-cyclocholestan-6β-ol (6a) (i-cholesterol) are readily available by solvolysis of cholesteryl p-tosylate in the corresponding

• cyclosteroid (i-steroid) rearrangement is a well-known steroid reaction [6]. The solvolysis of cholesteryl p-tosylate proceeds via the SN1 mechanism with the formation of a mesomerically stabilized carbocation. The addition of a nucleophile (alcohol, water, etc.) may occur either to C-3 or C-6, depending on

• –h was prepared including alkyl, aryl, and silyl ethers. Most of the compounds were prepared by solvolysis of cholesteryl p-tosylate in an appropriate alcohol (neat or mixed with dioxane) in the presence of potassium acetate as a buffer. TBDMS ether 6h was obtained by silylation of i-cholesterol 6a

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

• unexpectedly pronounced meta activation of substituted aryl phosphates. A strong ‘meta effect’ resulting in enhanced reaction efficiency by electron withdrawing, meta substituents is contrary to their ground state effects on solvolysis reactions which, instead, display enhanced reactivity for para substituents

• ) using Hückel molecular orbital theory [2][3], subsequently attributed by him to the positioning of conical intersections between the HOMO–LUMO PE surfaces [4][5]. He termed this phenomenon the “meta effect”, and generalized it for photochemical solvolysis reactions. Several additional photosolvolysis

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

• details are also consistent with the reaction rate of chlorophosphate with nucleophiles reported by Corriu et al. [28]. Indeed, they have shown that the second-order rate constants for the solvolysis of diethyl chlorophosphate with different nucleophiles including water, ethanol, phenol and diethylamine

A protecting group-free synthesis of the Colorado potato beetle pheromone

• Zhongtao Wu,
• Manuel Jäger,
• Jeffrey Buter and
• Adriaan J. Minnaard

Beilstein J. Org. Chem. 2013, 9, 2374–2377, doi:10.3762/bjoc.9.273

• the secondary alcohol at C-2. The synthesis by Faraldos runs via epoxidation of fluoronerol, subsequent acetylation of the alcohol and solvolysis. In 2010, Waymouth reported the chemoselective, catalytic oxidation of glycerol to dihydroxyacetone (Scheme 1) using catalytic [(neocuproine)PdOAc]2OTf2 (2

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• NO2 and O2 are much lower than that of I2, benzyl radicals generated from hydrogen abstraction by PINO react faster with the latter one, forming benzyl iodides selectively. Under the described reaction medium benzyl iodides undergo solvolysis, affording the corresponding benzyl acetates in excellent

Methylidynetrisphosphonates: Promising C₁ building block for the design of phosphate mimetics

• Vadim D. Romanenko and
• Valery P. Kukhar

Beilstein J. Org. Chem. 2013, 9, 991–1001, doi:10.3762/bjoc.9.114

• . Thus, heating 9 with Me3SiBr in dichloromethane followed by solvolysis in the presence tri-n-butylamine gave methylidynetrisphosphonic acid as its tris(tributylammonium) salt. This product was converted into its trisodium salt by precipitation from a methanol solution using a NaI solution in acetone [7

• group and the formation of bisphosphonic acid 39. Even with Me3SiBr/H2O, transsilylation and solvolysis under mild conditions afforded only the dephosphonylated product (Scheme 20) [43]. The result of the methylation of trisphosphonate 1a depends on the reagent: treatment of 1a with methyl p

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• ]. In the sequence displayed in Scheme 18, the addition–cyclisation of a malonyl radical to enyne 89 furnishes allenyl acetate 91 by cyclisation of propargyl radical 90 [41]. Compound 91 readily undergoes reductive dexanthylation and solvolysis into enone 92, and internal Michael addition to give

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• of 30. Packing diagram of 30. Structures of the different glycosylthiosemicarbazides. Glycosylations of oxadiazolinethione. Synthesis of glycosylthiosemicarbazides by solvolysis. Solvolysis of glycosylsulfanyloxadiazoles. Benzylation of the S- and N-glycosides 5–10. Aminolysis of benzylated indolyl-3

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

• Gert Callebaut,
• Sven Mangelinckx,
• Pieter Van der Veken,
• Karl W. Törnroos,
• Koen Augustyns and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2012, 8, 2124–2131, doi:10.3762/bjoc.8.239

• trapped by the deprotected β-amino group, as the deprotection of analogous anti-substrates under the same reaction conditions led to unprotected anti-α,β-diaminocarboxyl esters [18]. This is possibly due to the fact that solvolysis of the imine functionality with ethanol is not favorable and an acid

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• the aromatic ring and, thus, making the arene more susceptible towards SNAr reactions. Likewise, the benzylic and homo-benzylic positions in tricarbonyl(η6-arene)chromium complexes are more acidic and more prone to solvolysis, nucleophilic substitution and deprotonation than in the parent arenes due

Functionalization of anthracene: A selective route to brominated 1,4-anthraquinones

• Kiymet Berkil Akar,
• Osman Cakmak,
• Orhan Büyükgüngör and
• Ertan Sahin

Beilstein J. Org. Chem. 2011, 7, 1036–1045, doi:10.3762/bjoc.7.118

• Art and Science, Atatürk University, 25240, Erzurum, Turkey 10.3762/bjoc.7.118 Abstract Efficient and stereoselective syntheses are described for the preparation of 2,3,9,10-tetrabromo-1,4-dimethoxy-1,2,3,4-tetrahydroanthracenes 7, 8 and the corresponding 1,4-diol 17 by silver ion-assisted solvolysis

• selectivity both in their aromatization and silver-assisted solvolysis. On the other hand, most recently, we have developed an efficient stereoselective method to prepare hexabromide 6 [2][3] and opened up an efficient synthetic strategy for the synthesis of 3,9,10-tribromoanthracenes [2]. As an extension of

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• and only traces of the desired product were obtained. Under the mediation of aluminium oxide, this non-conjugated cyclopentylidene ketone product isomerized to the conjugated cyclopentenyl ketone 20. The authors proposed a solvolysis/cyclization mechanism for this gold-catalyzed cyclization, which was

• cyclization of internal diynes. Proposed solvolysis/cyclization mechanism. Gold-catalyzed cyclization of alkynyl epoxides and the 18O isotopic labeling experiment. Proposed oxygen transfer mechanism. Gold or silver-catalyzed cyclization of alkynyl epoxides and the corresponding deuterium labeling experiment.

Kinetic evaluation of the solvolysis of isobutyl chloro- and chlorothioformate esters

• Malcolm J. D’Souza,
• Matthew J. McAneny,
• Dennis N. Kevill,
• Jin Burm Kyong and
• Song Hee Choi

Beilstein J. Org. Chem. 2011, 7, 543–552, doi:10.3762/bjoc.7.62

• & Applied Chemistry, Hanyang University, Ansan-si, Gyeonggi-do, 426-791, Korea 10.3762/bjoc.7.62 Abstract The specific rates of solvolysis of isobutyl chloroformate (1) are reported at 40.0 °C and those for isobutyl chlorothioformate (2) are reported at 25.0 °C, in a variety of pure and binary aqueous

• activation values obtained from Arrhenius plots for 1 in these five solvents are reported. The specific rates of solvolysis were analyzed using the extended Grunwald–Winstein equation. Results obtained from correlation analysis using this linear free energy relationship (LFER) reinforce our previous

• chlorothioformate; solvolysis; Introduction Alkyl chloro- and chlorothioformate esters are frequently used precursors [1][2][3][4] in the synthesis of pharmaceutical intermediates. Hence, it is important to comprehend the correlations between their chemical structure, chemical reactivity, and solvent effects. This

β-Hydroxy carbocation intermediates in solvolyses of di- and tetra-hydronaphthalene substrates

• Jaya S. Kudavalli and
• Rory A. More O'Ferrall

Beilstein J. Org. Chem. 2010, 6, 1035–1042, doi:10.3762/bjoc.6.118

• Jaya S. Kudavalli Rory A. More O'Ferrall School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland 10.3762/bjoc.6.118 Abstract Solvolysis of trichloroacetate esters of 2-methoxy-1,2-dihydro-1-naphthols shows a remarkably large difference in rates between the

• cis and trans isomers, kcis/ktrans = 1800 in aqueous acetonitrile. This mirrors the behaviour of the acid-catalysed dehydration of cis- and trans-naphthalene-1,2-dihydrodiols to form 2-naphthol, for which kcis/ktrans = 440, but contrasts with that for solvolysis of tetrahydronaphthalene substrates, 1

• -chloro-2-hydroxy-1,2,3,4-tetrahydronaphthalenes, for which kcis/ktrans = 0.5. Evidence is presented showing that the trans isomer of the dihydro substrates reacts unusually slowly rather than the cis isomer unusually rapidly. Comparison of rates of solvolysis of 1-chloro-1,2,3,4-tetrahydronaphthalene and

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• parent free aziridine 114 in 65% yield. Although these types of aziridinomitosene are usually very unstable and aziridine solvolysis products are often formed, the presence of a deactivating ester group promoted the stability of the molecule. 4.3. Reissig. Addition of samarium ketyls to alkynes The

• functionalized mitosene W.A. Remers used a similar approach to build the quinone ring of a 1,2-disubstituted mitosene [135]. The target compound had an arrangement of the C1 and C2 substituents opposite to that found in mitomycin solvolysis products. Unfortunately, these compounds did not show any anti-tumour