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Search for "epoxide" in Full Text gives 248 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Synthesis of enantiomerically pure N-(2,3-dihydroxypropyl)arylamides via oxidative esterification
Beilstein J. Org. Chem. 2013, 9, 2129–2136, doi:10.3762/bjoc.9.250
- good overall yields in a two step process. The key step involves the ring opening of the chiral epoxide with a nitrogen heterocyclic carbene (NHC) and further rearrangement to chiral N-(2,3-dihydroxypropyl)arylamides in high yields and enantioselectivity. During the reaction, no erosion in chiral
- . The phthalimido-protected chiral hydroxypropyl benzoate 5a could be synthesized by the reaction of nitrogen heterocyclic carbene, benzaldehyde and phthalimido-epoxide 4a. Phthalimido-epoxide 4a was synthesized by treating (S)-glycidol (3) with phthalimide (2) under Mitsunobu reaction conditions
- ]. When the reaction was conducted under nitrogen atmosphere, product formation was not observed. If the reaction was carried out in air, it was found that ester 5a was obtained as the only product in the presence of NHC. When a diol instead of an epoxide was used as a substrate for the oxidative
The chemistry of isoindole natural products
Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243
- reduction, acetylation and a magnesium sulfate induced rearrangement of the epoxide to the allylic alcohol. The synthesis of cytochalasin B 52 (15 steps from 73) proceeded in a similar fashion and was highlighted in detail by Hertweck [44]. The authors state that this approach is highly diversifiable and
- isopentyl pyrophosphate (IPP, 166), and orsellinic acid (168), which is derived from a fungal iterative type I polyketide pathway [142], are connected to give 169. This substrate is already poised for a polyene cyclization cascade, which only has to be triggered via activation of the epoxide. After the
- induced domino epoxide-opening/rearrangement/cyclization cascade was accomplished by the group of Katoh (Scheme 22) [144]. The synthesis commenced with the conversion of dimethyl 2,6-dihydroxyterephthalate (172) to nitrile 173 within five consecutive steps. Hydrogenation and lactam formation of 173 gave
A concise enantioselective synthesis of the guaiane sesquiterpene (−)-oxyphyllol
Beilstein J. Org. Chem. 2013, 9, 2028–2032, doi:10.3762/bjoc.9.239
- the total synthesis of the anticancer guaiane (−)-englerin A. A regio- and diastereoselective Co(II)-catalyzed hydration of the olefin and a transannular epoxide opening were used as the key reactions. Keywords: asymmetric synthesis; hydration; natural products; terpenes; transannular epoxide opening
- 3 can be utilized to generate the isopropyl group, and a regioselective transannular epoxide opening would construct the oxygen-bridged bicyclic hydroazulene framework. Alcohol 3 was traced back to the known epoxy enone 4 that already served as an intermediate for the total synthesis of 5 [6]. As
- envisaged deoxygenation route (Scheme 2), this key transformation saved 2 steps and paved the way for a final reaction sequence that was based on our synthesis of (−)-englerin A (5) [6]. Thus, Wittig olefination of the acetyl group in 3 afforded the sensitive vinyl epoxide 10 along with some cyclized
Stereoselective synthesis of the C79–C97 fragment of symbiodinolide
Beilstein J. Org. Chem. 2013, 9, 1931–1935, doi:10.3762/bjoc.9.228
- ). Treatment of epoxide 13, which was prepared from L-aspartic acid (12) by the known procedure [8], with 3-butenylmagnesium bromide/CuI [16] provided the corresponding secondary alcohol. Protection of the alcohol with TBSCl afforded TBS ether 14 in 91% yield in two steps. Alkene 14 was reacted with m-CPBA to
- produce epoxide 15 as a 1:1 diastereomeric mixture. Epoxide 15 was coupled with alkyne 16 [4] in the presence of n-BuLi/BF3∙OEt2 [17] to give the desired product 17 in 92% yield from 15. Hydrogenation of the alkyne moiety of 17 followed by TPAP oxidation [18] yielded ketone 18. Removal of the three TBS
Activation of cryptic metabolite production through gene disruption: Dimethyl furan-2,4-dicarboxylate produced by Streptomyces sahachiroi
Beilstein J. Org. Chem. 2013, 9, 1768–1773, doi:10.3762/bjoc.9.205
- . sahachiroi genome and is the first non-azinomycin related compound to be isolated from the S. sahachiroi strain (Figure 1). Previously isolated metabolites consisted of azinomycin intermediates lacking the 1-azabicyclo[3.1.0] ring system, including naphthoate and naphthoate epoxide derivatives [11]. The
- could be envisioned to form through nucleophilic attack of an epoxide as in the case with monensin and other similar natural products [16]. Alternatively, the biosynthesis might involve the dimerization of pyruvate [17][18][19]. Examination of a draft genome sequence of the S. sahachiroi strain has
Organocatalyzed enantioselective desymmetrization of aziridines and epoxides
Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192
- emerged as a cutting-edge approach in recent years. This review summarizes the origin and recent developments of enantioselective desymmetrization of meso-aziridines and meso-epoxides in the presence of organocatalysts. Keywords: aziridine; desymmetrization; enantioselectivity; epoxide; organocatalysis
- enantioselective desymmetrization of a phospholene meso-epoxide by cinchona alkaloids to P,C-chirogenic 3-hydroxy-2-phospholene derivatives 93 and 94. Among the four main components of cinchona alkaloids, quinidine (OC-57) proved to be the most effective base in the enantioselective rearrangement of epoxide, and
- was 87% ee. The proposed reaction mechanism is depicted in Figure 14. The first step of the catalytic cycle is the activation of SiCl4 by chiral phosphoramide OC-62 to form a complex, which was ionized to produce a highly reactive silicon cation and a chloride ion. The epoxide was activated by the
Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines
Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185
- , this approach was employed in the investigations of the following intramolecular radical additions to arenes. Investigation of the radical addition to substituted anilines In our preparative work, we have been mostly concerned with the catalytic synthesis of indolines via addition reactions of epoxide
Synthesis and biological activities of the respiratory chain inhibitor aurachin D and new ring versus chain analogues
Beilstein J. Org. Chem. 2013, 9, 1551–1558, doi:10.3762/bjoc.9.176
- the double oxidation of the quinolone nitrogen and the olefin epoxidation (2',3'-position) of the farnesyl chain, with the epoxide being ring-opened with 5-exo selectivity by the 4-hydroxy group of the resulting 4-hydroxyquinoline N-oxide. Taking the geranyl analogue 9 as a model compound (Scheme 2
A reductive coupling strategy towards ripostatin A
Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175
- construct the C9−C10 bond by a nickel(0)-catalyzed coupling reaction of an enyne and an epoxide, followed by rearrangement of the resulting dienylcyclopropane intermediate to afford the skipped 1,4,7-triene. A cyclopropyl enyne fragment corresponding to C1−C9 has been synthesized in high yield and
- demonstrated to be a competent substrate for the nickel(0)-catalyzed coupling with a model epoxide. Several synthetic approaches toward the C10−C26 epoxide have been pursued. The C13 stereocenter can be set by allylation and reductive decyanation of a cyanohydrin acetonide. A mild, fluoride-promoted
- decarboxylation enables construction of the C15−C16 bond by an aldol reaction. The product of this transformation is of the correct oxidation state and potentially three steps removed from the targeted epoxide fragment. Keywords: catalysis; natural product; nickel; reductive coupling; ripostatin A; synthesis
Synthesis of the calcilytic ligand NPS 2143
Beilstein J. Org. Chem. 2013, 9, 1383–1387, doi:10.3762/bjoc.9.154
- . Similar to a previously reported synthesis of (R)-3 [13], we decided to activate epoxide 5 as the m-nosyl derivative that has been shown to minimise racemisation during epoxide ring opening [15]. The synthesis of amine 6 was accomplished from commercially available 2-cyanonaphthalene (7) in four steps
- . 1H NMR analysis of the crude product showed the presence of approximately 5–10% of a structurally similar side-product that proved extremely difficult to remove by chromatography. The side product is likely the regioisomer formed by nucleophilic attack on the more sterically hindered epoxide carbon
Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review
Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146
- presence of the radical scavenger BHT no conversion was observed. (ii) The exclusion that epoxide could be an intermediate of the process. When 2-methyl-2-phenyloxirane was used in place of α-methylstyrene, poor results were obtained in terms of yield in acetophenone. (iii) The proof that the oxygen atom
Exploration of an epoxidation–ring-opening strategy for the synthesis of lyconadin A and discovery of an unexpected Payne rearrangement
Beilstein J. Org. Chem. 2013, 9, 1179–1184, doi:10.3762/bjoc.9.132
- Brad M. Loertscher Yu Zhang Steven L. Castle Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT, 84602, USA 10.3762/bjoc.9.132 Abstract In the context of synthetic efforts targeting the alkaloid lyconadin A, scalemic epoxide 25 was prepared by a highly
- stereoselective sequence involving a Myers alkylation and a Shi epoxidation. Ring-opening of this epoxide with a vinylcopper complex afforded alcohol 26 instead of the expected product 27. An unusual Lewis acid promoted Payne rearrangement of an α-trityloxy epoxide is proposed to account for this outcome
- course of this work, we discovered an unusual Payne-like rearrangement process that occurred in preference to the ring-opening of a hindered epoxide. Results and Discussion Our retrosynthetic analysis of lyconadin A is shown in Scheme 1. We reasoned that 1 could be formed by an alkylation cascade
Efficient regio- and stereoselective access to novel fluorinated β-aminocyclohexanecarboxylates
Beilstein J. Org. Chem. 2013, 9, 1164–1169, doi:10.3762/bjoc.9.130
- stereoisomer of 5 (Scheme 3, Figure 4). It is noteworthy that in this latter case hydroxylated amino ester 14 could not be prepared by the alternative diastereoselective epoxidation and regioselective oxirane opening strategy: according to our previous results, the opening of epoxide 15 derived from 10
Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation
Beilstein J. Org. Chem. 2013, 9, 1135–1140, doi:10.3762/bjoc.9.126
- this intermediate to Jones oxidation triggered a highly efficient oxidation–epoxide opening [93][94][95][96][97][98] reaction cascade [99][100] to construct the critical D-ring of 9 (46% yield, over 3 steps). Notably, this scalable approach rendered us several hundred milligrams of compound 9, paving
New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators
Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101
- the cationic polymerization of the epoxide (r11 in Scheme 5). For the other Co_Py, a good thermal stability is found. This dual behavior of some Co_Pys, which are able to initiate both a thermal and a photochemical cationic polymerization, can be very useful to initiate the polymerization in the
Some aspects of radical chemistry in the assembly of complex molecular architectures
Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61
- xanthate 51 and proceeding via adduct 52, underscores the tolerance of the process for the presence of an epoxide and, at least in this case, of a free phenol [29]. This sequence represents an attractive potential route to seco-pseudopteroxazole, 54, and to other congeners in this family. In many cases
- epoxide as an allylating agent are displayed in Scheme 27 [59]. The first corresponds to the allylation of cyclobutyl xanthate 143 with vinyl epoxide 144 to yield compound 145, while the second involves an addition–fragmentation of xanthate 146 on β-pinene to give xanthate 147, which is then subjected to
- the allylation procedure with the simplest vinyl epoxide to furnish derivative 148. It is interesting to note that the carbon–carbon bond formation takes place in ketoester xanthate 146 on the carbon bearing the least acidic hydrogens. Triethylborane, through its autoxidation, serves to initiate the
Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids
Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56
- oxide (1) under solvent-free conditions. The epoxide ring-opening reactions were carried for 24 h at elevated temperature (32 °C) and resulted in the formation of the appropriate alcohols (±)-3a and (±)-3b in high yields (Scheme 1). In the next step, the influence of crucial parameters in enzyme
Microwave-assisted three-component domino reaction: Synthesis of indolodiazepinotriazoles
Beilstein J. Org. Chem. 2013, 9, 401–405, doi:10.3762/bjoc.9.41
- Abstract A microwave-assisted three-component protocol involving N-1 alkylation of 2-alkynylindoles with epichlorohydrin, ring opening of the epoxide with sodium azide, and an intramolecular Huisgen azide–internal alkyne 1,3-dipolar cycloaddition domino sequence has been described. The efficacy of the
- functionalized with epoxide by reacting 2-alkynylindole with epichlorohydrin. This can then be followed by ring opening of the oxirane by azide to furnish a bis-functionalized indole intermediate having azide and alkyne groups in close proximity. Such an intermediate may then undergo annulation following an
- product in 77% isolated yield within 1 h (Table 1, entry 6). Further stirring up to 4 h at 120 °C led to the partial conversion of 4a (by ring opening of the epoxide with NaN3) into yet another intermediate 1-azido-3-{2-[2-(4-methylphenyl)ethynyl]-1H-indol-1-yl}propan-2-ol (5a, Table 1, entry 7) in 30
Polar reactions of acyclic conjugated bisallenes
Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5
- bisallenes, including the tetramethyl derivative 2, were epoxidized by Pasto et al. [26]. These authors showed that this hydrocarbon provides the products 35 and 36 on treatment with m-chloroperbenzoic acid (MCPBA) in dichloromethane (product ratio: 71:29). With excess dimethyldioxirane (DMDO) the epoxide 37
- 36 are identical with those given in the literature [26]. As far as the oxidation mechanism is concerned it agrees with the suggestion of Pasto (see above). When the epoxidation reagent was employed in excess (fivefold) the epoxide 37 was produced in 66% yield (with reference to 2) as a colorless oil
- resulted in the formation of 68% of 38 and a trace amount of the epoxide 39 (8%), while 24% of the substrate was recovered (GC analysis). Since the complete separation of the two products was difficult, the experiment was repeated with excess MMPP (1.5 equiv); in this case the yield of 39 was 62% and the
Total synthesis and biological evaluation of fluorinated cryptophycins
Beilstein J. Org. Chem. 2012, 8, 2060–2066, doi:10.3762/bjoc.8.231
- suggests four different fragments to be assembled in the total synthesis, named unit A–D (Figure 1). Unit A is an α,β-unsaturated δ-hydroxy acid that usually also contains a benzylic epoxide or a benzylic double bond. Unit B represents a chlorinated O-methyl-D-tyrosine derivative, while unit C is a β2
- from this transformation was directly subjected to reaction with acetyl bromide to form a bromohydrin formate. This was then treated with a potassium carbonate/ethylene glycol/dimethoxyethane-emulsion to bring about cleavage of the formyl ester accompanied by epoxide formation as previously described
- concomitantly displaced the trichloroethylester at unit B to result in the macrocyclic product 30 [34]. Cleavage of the dioxolane liberated the vicinal diol, which was then subjected to the final diol-epoxide transformation to provide the cryptophycin-52 analogue 31 in a yield of 14% over the final four steps
Flow photochemistry: Old light through new windows
Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229
The chemistry of bisallenes
Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225
- fact we could only find two references describing photoreactions involving bisallenes. Thus, irradiation of the epoxide 197 in benzene-d6 (NMR experiment) yielded a plethora of photoproducts, among them two photodimers to which structure 198 was assigned by spectroscopic measurements (Scheme 47) [136
- cyclopentenones [140]. Applying the mechanism discussed in this latter context to 24, it is reasonable to propose the formation of an allene-epoxide first [141], which can exist either in a transoid, 212, or cisoid conformation, 213 (Scheme 51). Whereas the former could open up to the “stretched” zwitterion 214
Alkenes from β-lithiooxyphosphonium ylides generated by trapping α-lithiated terminal epoxides with triphenylphosphine
Beilstein J. Org. Chem. 2012, 8, 1896–1900, doi:10.3762/bjoc.8.219
- LTMP and PPh3 in THF at 0 °C for 24 h, gave no colour change from an initial yellow solution), becoming very intense after 3 h, although some epoxide 11 was still present after 24 h (TLC monitoring); the reduced activity of LTMP may be due to phosphine coordination [32]. At this point, following
- the presence of soluble lithium halides [33][34], the homoallylic alcohol, which would arise [35] from any reaction of β-lithiooxyphosphonium ylide and terminal epoxide, was not observed in the present studies; this suggests that the latter ylides are not capable of reacting with terminal epoxides [35
- TMP enamine) [36][37]. In the present work, neither decanal nor its corresponding TMP enamine were not detected as side-products, and we also established that the presence of LiBr (1 equiv) did not interfere in this isomerization process, giving decanal from epoxide 11 in 65% yield (67% without LiBr
Imidazolinium and amidinium salts as Lewis acid organocatalysts
Beilstein J. Org. Chem. 2012, 8, 1798–1803, doi:10.3762/bjoc.8.205
- as racemate in the error range of the HPLC measurements. Next, several salts were explored in the ring opening of cyclohexene epoxide with aniline (Scheme 4, Table 2). A reaction in CH2Cl2 in the absence of the catalyst gave a yield of 10% after 24 h (Table 2, entry 1). The camphor based salt 16 gave
- %, respectively (Table 2, entries 6 and 7). Compared to sulfur, oxygen is a good hydrogen-bond acceptor. Hence, also imidazolinium salts with a C(2)H unit were applied in the reaction. Here, an activation of the epoxide can be also possible through hydrogen bonding next to the direct interaction with the
- –Alder reaction with ethyl crotonthioate (1) and cyclopentadiene (2). Diels–Alder reaction catalysed with imidazolinium salts. Ring opening of thiirane 12. Ring opening of epoxide 14. Synthesis of bis-imidazolium salt 17. Synthesis of amidinium salt 21. Diels–Alder reaction with 10 mol % catalyst
Synthesis and ring openings of cinnamate-derived N-unfunctionalised aziridines
Beilstein J. Org. Chem. 2012, 8, 1747–1752, doi:10.3762/bjoc.8.199
- -opening protocols have been developed, synthesis of the starting NH-aziridine-2-carboxylates is multistep and low-yielding. Synthetic routes include Gabriel–Cromwell addition of ammonia to an enoate [16][17]; epoxide opening with azide, followed by ring closure [19]; and a sequence of olefin
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