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Search for "hydrogenolysis" in Full Text gives 170 result(s) in Beilstein Journal of Organic Chemistry.
Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs
Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179
- oxidation conditions. Based on this assumption, the corresponding silyl nitronate from 3-nitropropanal or its acetal were not tried for cycloaddition. We then set to liberate the β-hydroxy ketone synthon by ring opening of the isoxazoline 3 (Scheme 3). Raney-Ni-catalyzed hydrogenolysis in the presence of
- of the desired β-hydroxy ketone was observed. In our experience, the hydrogenolysis of a 2-isoxazoline having a 5-ester group was troublesome. Thus, the 5-ester group was reduced with NaBH4 to give 5. The hydroxy group was subsequently protected with benzoyl (Scheme 3), which also worked as a
- exemplified in Scheme 2. These results prompted us to try the oxidation in a later stage. When 6 was subjected to Raney-Ni-catalyzed hydrogenolysis, the desired β-hydroxy ketone 7 was obtained in 85% yield (Scheme 3). Under the weakly acidic conditions, the THP group survived. Next, a Narasaka–Prasad
Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides
Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174
- condensation reactions with hydroxyisobutyryl and glycolyl mannosides. The synthesis of desmuramyl peptide 7 with an adamantane moiety bound at C-terminus is presented in Scheme 2. After hydrogenolysis of the starting dipeptide, condensation of free carboxyl group with adamant-1-ylamine hydrochloride was
N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds
Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168
- compounds were obtained in a 84:16 ratio. The major ether (2R,1'R)-26, which emerged from the displacement of the tosyloxy group (path a), was accompanied by (2S,1'R)-26 which came from the aziridine ring opening at C3 (path b). After chromatographic purification and hydrogenolysis enantiomerically pure (R
- was followed by the aziridinium ion opening with cyanide to access compound 64 which was first transformed into diester and later after hydrogenolysis into the γ-lactam (S)-65 [62]. The methoxycarbonyl to acetyl group conversion was accomplished via Weinreb amide to give the pyrrolidin-2-one (S)-66
- readily accomplished [78] from the aziridine alcohol (2R,1'R,1''S)-28 available by addition of phenyllithium to the aldehyde (2R,1'S)-6 [30]. Opening of the aziridine ring in (2R,1'R,1''S)-28 with acetic acid yielded the acetate (1R,2R,1'S)-106 while catalytic hydrogenolysis led to the formation of (1R,2R
An azobenzene container showing a definite folding – synthesis and structural investigation
Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156
- protective group, the resulting amino acid was cyclodimerized to the benzyl-protected macrocycle. The yield for the cyclization amounts to about 50%. The last step was the removal of the benzyl group by hydrogenolysis to yield the desired macrocycle 3a. The cyclopeptide 2a [52] is commercially available
Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy
Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135
- pseudoaxial substituents. The alternative, a more stable transition state formed from the re-face attack would bear to the actually obtained 3S configurated boronic acid analogue 7. The final deprotection of compound 7 by conventional catalytic hydrogenolysis gave the final compound 8 in almost quantitative
- [19], again with 5 equiv of reagent, afforded the cyclic boronic acid 10 in a fair yield. Benzylidene group hydrogenolysis gave the deprotected pure cyclic boronic acid 11 in quantitative yield and compound 11 proved to be stable for months. In this case the elimination reaction was not observed as
The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives
Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61
- ]. The methoxy-substituted compound PM2 requires harsh conditions employing trimethylsilyl iodide at 80 °C to provide the intermediate hydroxy derivative PM51. In contrast, the removal of the benzyl group in PM20 can be achieved by palladium-catalyzed hydrogenolysis at room temperature to give hydroxy
- alternative to the strongly acidic conditions, palladium-catalyzed hydrogenolysis of the benzyloxy-substituted derivatives is possible, thus avoiding the condensation to oxazoles. Scheme 25 shows the conversion of KE52 into 1,2-diketone DK14 (compare entry 3 of Table 6). Longer reaction times lead to a
Design and synthesis of multivalent α-1,2-trimannose-linked bioerodible microparticles for applications in immune response studies of Leishmania major infection
Beilstein J. Org. Chem. 2019, 15, 623–632, doi:10.3762/bjoc.15.58
- , hydrogenolysis of the benzyl ethers under continuous flow (0.3–1 mL/min) and H2 pressure (30–60 bar) using an H-cube apparatus was found to be effective at removing the benzyl ethers, but arduously slow (>48 h) from the limited surface-mediated interactions with the Pd/C cartridge. By comparison, batch
- hydrogenolysis at 1 atm pressure hydrogen afforded the fully deprotected trimanose 16 in just 24 h. To further reduce the total number of benzyl groups, the simpler peracylated TCA donor 4 was used to cap the oligosaccharide. The benzyl-protected nitrogen proved unnecessary and was difficult to deprotect under
Synthesis of the aglycon of scorzodihydrostilbenes B and D
Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56
- , the yield was lower (Scheme 2). In order to bring about the cleavage of the benzyl protecting groups in the ketones 8a and 8b by hydrogenolysis [17][18], various metal catalysts were tested. It turned out that palladium on charcoal was the only catalytic system that provided satisfying results. Ethyl
- , partial hydrogenation of the aromatic rings had to be suppressed. Nevertheless, the aglycon 9 of scorzodihydrostilbenes B and D (2 and 4) was obtained in good yield from 8a. Hydrogenolysis of ketone 8b led to hydroquinone 10, however, along with a minor amount of mono-deprotected phenol 11. The main
A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12
Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42
- the amine using LiAlH4 with concomitant debenzoylation, followed by the acylation of the amine with lauric acid to afford 9a, and finally, ii) reductive cleavage by hydrogenolysis using Pd–C/H2 leading to debenzylation (Scheme 3). However, during hydrogenolysis, the elimination of the -OBn group led
- to product 9b, which was undesirable. A similar elimination was earlier observed by Sharf et al. during hydrogenolysis of dibenzyl ether [55]. To avoid this, an oxidative debenzylation of 9a using DDQ/CH2Cl2–H2O was carried out. However, this led to a very poor yield of the target compound 2 (Scheme
Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae
Beilstein J. Org. Chem. 2019, 15, 431–436, doi:10.3762/bjoc.15.37
- reaction conditions furnished the D-glucuronic acid containing pentasaccharide derivative, which on global deprotection under hydrogenolysis in the presence of Pearlman’s catalyst [40] afforded the target pentasaccharide as its 2-aminoethyl glycoside 1 in 61% yield (Scheme 4). Conclusion In summary, a
Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives
Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36
- the corresponding protected derivative 30 was low (Scheme 15). Yet, this particular protecting group is easily removed under mild acidic conditions, such as diluted HCl in organic solvents (THF/MeOH) or 90% aqueous trifluoroacetic acid or hydrogenolysis. 3.3. Reduction of the pyridinium core of NR
Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes
Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29
- achieved in the presence of Pd/C as a catalyst. Concomitant hydrogenolysis of two carbon–chlorine bonds also took place under these conditions and a 71:29 diastereomeric mixture of the monochloracetamides 19f/19’f was obtained (41%). The rather small difference of steric hindrance between the methyl and
Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials
Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28
- mild conditions, hydrogenolysis of the benzyl ester group to the carboxylic acid and hydrogenation of the C=C double bonds at the silicon atoms (Scheme 7). The ability of the obtained derivatives, in particular the carboxylic acids, to generate nanostructured materials through self-organization
Synthesis of nonracemic hydroxyglutamic acids
Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22
- basic hydrolysis of the formate to afford the acid (2S,3R)-61. Its allylation provided the ester (2S,3R)-62, a protected precursor of 3-hydroxyglutamate, from which (2S,3R)-2 can be prepared by catalytic hydrogenolysis (Scheme 15) [67]. 4-Hydroxyglutamic acids All enantiomers of 4-hydroxyglutamic acid
- protected 3,4-dihydroxy-L-glutamic acid 96 and the respective γ-lactone 97 formed from 96 in the presence of acids. Benzyl alcohol was selected to refrain from decomposition of the final amino acids during the acid hydrolysis of, e.g., methyl esters [99] since for a mixture of 96 and 97 hydrogenolysis
- final step transesterification of methyl to benzyl esters was successfully performed in the presence of titanium(IV) benzyloxide to afford dibenzyl esters 102 and 103, respectively. Their hydrogenolysis cleanly produced (2S,3S,4S)-104 and (2S,3S,4S)-105 [103]. From tartaric acids Four-carbon chirons
Synthesis of 1,4-imino-L-lyxitols modified at C-5 and their evaluation as inhibitors of GH38 α-mannosidases
Beilstein J. Org. Chem. 2018, 14, 2156–2162, doi:10.3762/bjoc.14.189
- of acetonides 9 and 12 gave target compounds 2a (64%) and 3a (68%, Scheme 1). As amines prepared by catalytic hydrogenolysis of N-benzylpyrrolidines 9 and 12 were extremely volatile they were immediately subjected to acetonide hydrolysis without isolation. So-obtained hydrochlorides were used
- achieved by N-debenzylation under catalytic hydrogenolysis conditions followed by protection of the liberated amines with CbzCl furnishing fully protected pyrrolidines 14 [35] and 15. Exposure of 14 to a catalytic amount of PTSA (0.04 equiv) in a mixture of CH2Cl2/MeOH 30:1 (v/v) resulted in rapid cleavage
- hydrogenolysis conditions furnished the free amine which was subsequently subjected to N-benzylation with the corresponding (4-halo)benzyl bromide to afford N-(4-halo)benzylpyrrolidines 19a–c. Acidic hydrolysis of the acetonide protecting group in 19a–c provided target compounds 4a–c in good yields (Scheme 3
A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols
Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105
- tried to remove the OH group using the Pd-catalytic hydrogenolysis (Scheme 3). In case of 6b (X = S), no reaction occurred and only the substrate was recovered, most probably due to poisoning of the catalyst by the 1,3-dithianyl sulfur atoms. However, the successful catalytic hydrogenolysis (5% Pd/C) of
- hydrogenolysis or pyrolysis of the corresponding ortho-1,3-dioxolanyl [65] and ortho-hydroxymethyl [66] substituted diarylmethanols, respectively. It is worth mentioning that the reduction of 9 with ZnI2–Na(CN)BH3 caused decomposition of the starting material. The described reduction process involving 1,3
- )methanes in 26–95% yields under mild reaction conditions. Thus, the ortho-1,3-dithianyl moiety joins other functionalities tolerated by this reagent system [47]. Since analogous 1,3-dioxanyl derivatives, in our hands, decomposed or led to other products during the attempted catalytic hydrogenolysis, the
The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series
Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85
- with benzophenone imine and subsequent hydrogenolysis. Keywords: aminoestrones; Buchwald–Hartwig amination; 13α-estrone; functionalization; microwave assisted reactions; Introduction Aminoestrones are of particular interest thanks to their diverse biological applications [1][2][3][4]. There exist
- -13α-estrone (13). The efficient C(sp2)–N coupling method elaborated above proved to be suitable for the reaction of 2-bromo-3-benzyl ether 2 and benzophenone imine as an amine precursor (Scheme 2). The deprotection was achieved by hydrogenolysis using a Pd/C catalyst. The resulting newly-synthesized 2
Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review
Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33
- mechanism for this step is analogous to the mechanism for ketal or acetal formation except sulphur replaces oxygen as the nucleophile attacking the carbonyl group. In a second step, the dithioketal is reduced to the corresponding methylene compound by hydrogenolysis in presence of Raney Nickel (actually
Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines
Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30
- residues. Acid catalysed hydrolysis of the 4,6-benzylidene was followed by regioselective glycosylation of the primary 6-OH with a different pentasaccharide, this time comprised of five mannoses. Conversion of the azide to acetamide and removal of all benzyl groups by hydrogenolysis produced a completely
Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline
Beilstein J. Org. Chem. 2018, 14, 130–134, doi:10.3762/bjoc.14.8
- , after quaternization with iodomethane, is easily converted into the desired 1-methylisoquinoline by hydrogenolysis of both the benzylamine and benzyl ether groups. Keywords: alkaloid; aminomethylation; hydrogenolysis; isoquinoline; metalation; methylation; Introduction The isoquinoline ring system has
- hydrogenolysis experiments with 5, which were aimed at simultaneous O-debenzylation at the 7-position and conversion of the N,N-dimethylaminomethyl group at C1 into a methyl group. Hydrogenation in presence of palladium as catalyst at 1 bar in the presence or absence of small amounts of sulfuric acid gave the
- phenolic product 6 in high yield with unchanged N,N-dimethylaminomethyl group. The same result was obtained at high pressure (40 bar) and upon addition of formic acid for accelerating hydrogenolysis [21]. Obviously, and in contrast to earlier reports on related naphthol Mannich bases [20], the benzylamine
Aminosugar-based immunomodulator lipid A: synthetic approaches
Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3
- TBS ether by treatment with HF in pyridine, followed by phosphorylation using tetrabenzyl pyrophosphate in the presence of lithium bis(trimethyl)silylamide [76] in THF at −78 °C. Final deprotection by catalytic hydrogenolysis over Pd-black provided target lipid A derivatives 8 and 9 corresponding
- hydroxyl group was regio- and stereoselectively phosphorylated using tetrabenzyl diphosphate in the presence of lithium bis(trimethylsilyl)amide [76] to provide glycosyl phosphotriester as exclusively α-anomer. Global deprotection was accomplished by catalytic hydrogenolysis over Pd-black to give
- pyrophosphate to furnish exclusively α-configured fully protected glycosyl phosphotriester. Global deprotection by catalytic hydrogenolysis over Pd-black gave E. coli lipid A functionalized with the glutaryl-Glc linker 23 which served as a key precursor for the preparation of fluorescent- or biotin-labeled
From dipivaloylketene to tetraoxaadamantanes
Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1
- 21 and 22, but carboxylic acid derivatives are preserved to yield compounds 20, 23, 25, 28, and 29. A hydrogenolysis of the dibenzyl ester 23 yields the free dicarboxylic acid 24. The tetraoxaadamantanes are formed in high yields (65–95%) in most cases, but the addition of water to the concave inside
- reaction (Scheme 7), and not in the final products, which are not prone to decarboxylation: the stable bis-carboxylic acid 24 can be obtained by hydrogenolysis of the dibenzyl ester 23 (Scheme 6) [30]. The reaction may be seen as a decarboxylative [31][32] oxa-Michael addition (Scheme 7) and may be related
The synthesis of the 2,3-difluorobutan-1,4-diol diastereomers
Beilstein J. Org. Chem. 2017, 13, 2883–2887, doi:10.3762/bjoc.13.280
- a very small extent. Separation of the diastereomers proved not possible. Finally, deprotection of (±)-syn-4 by palladium catalysed hydrogenolysis led to (±)-syn-5. Recrystallization to remove the minor diastereomer was not successful. Conclusion A gram-scale synthesis of both syn- and anti-2,3
Phosphonic acid: preparation and applications
Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219
- monohydrolysis can be also achieved using NaI as nucleophile in acetone [147] or butanone as solvent [148]. 3.2. Catalytic hydrogenolysis Dibenzyl phosphonates are readily synthesized using dibenzyl or tribenzyl phosphite. This type of phosphonate offers an alternative to the use of acidic conditions to prepare
- phosphonic acid since the benzyl moieties can be removed by hydrogenolysis (Figure 12). Palladium on charcoal, which is the most used method to prepare phosphonic acid from dibenzyl phosphonate [149], was the catalyst used to prepare the phosphonic acids 33 [150], 34 [151] and 35 [152] (Figure 12). Of note
- as exemplified by the preparation of the compounds 36 [154] and 37 [155] (Figure 13). It is also worth noticing that phosphonic acid can be prepared by the hydrogenolysis of diallyl phosphonates. For this purpose the use of the Wilkinson catalyst (ClRh(PPh3)3) was reported [156]. 3.3. McKenna’s
A mechanochemical approach to access the proline–proline diketopiperazine framework
Beilstein J. Org. Chem. 2017, 13, 2169–2178, doi:10.3762/bjoc.13.217
- it would avoid a potential pressure build-up (release of CO2) which could occur with NaHCO3. Noteworthy, no epimerization could be detected by NMR or HPLC analyses. Both peptides 7 and 8 were then deprotected and cyclized into the corresponding diketopiperazine 9. Palladium-catalyzed hydrogenolysis
- ). Pyrrolidine cis-11 is an N-protected amino ester, which can be used in the synthesis of diketopiperazines by deprotecting either the amino group or the ester function. Hydrogenolysis of the benzyl group of cis-11 provided the nitrogen-free pyrrolidine derivative 12 in excellent yield and purity after
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