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Search for "pyran" in Full Text gives 100 result(s) in Beilstein Journal of Organic Chemistry.
Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis
Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269
- –71%, respectively (Scheme 29) [42]. An interesting example of the application of ylides derived from vinylphosphonium salts in the enantioselective synthesis of pyran derivatives was reported by Ley et al. in 2010. β-Hydroxyaldehyde 43 as the oxygen nucleophile was obtained here in the asymmetric
- , followed by the intramolecular Wittig reaction gave the corresponding 3,6-dihydropyran derivatives 44 in yields of 34–56% and a high enantioselectivity of 95–98% (Scheme 30) [43]. Pyran derivatives are structural elements of many natural biologically active compounds [44][45][46][47]. 2.2.2. Reactions with
Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies
Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221
- product [30] (Scheme 6). The analogous reaction with phenyl vinyl sulfide (22) gave the expected cyclobutane 23 exclusively. However, in the absence of ZnCl2, a mixture of 23 and 3,4-dihydro-2H-pyran 24 was obtained, with the latter compound formed through a competitive hetero-Diels–Alder reaction [30
- ]. The competitive formation of cyclobutane and pyran derivatives was also observed in reactions of E-1b or Z-1b with ethyl prop-1-enyl ether performed in CDCl3 at room temperature [31]. The reaction of N-vinylcarbazole (25) with E-1b or Z-1b in boiling benzene gave mixtures of four diastereoisomers of
- carried out [45][48][50][51]. A stepwise reaction has also been suggested for the formal [4 + 2]-cycloaddition of E- and Z-1b with ethyl prop-1-enyl ether leading to a mixture of the corresponding 3,4-dihydro-2H-pyran and cyclobutane derivatives in a non-stereospecific manner [31]. A mechanism with the
Mechanochemical synthesis of small organic molecules
Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186
- ]. Mechanochemical methods of the Mannich reaction, Paal–Knorr synthesis, Bigineli reaction, Hantzsch reaction, and syntheses of substituted pyran, thiophene, isoquinoline derivatives, etc. are also reported [104][107][112][113]. Isocyanide-based multi-component reactions are also well known [114][115]. Recently, in
- example, a) at higher frequency (800 min−1) for 45 min lower yield with less selectivity was observed and b) using lower frequency, 200 min−1 for 8 h led to 82% of yield with high selectivity. In the traditional method of pyran synthesis the use of transition metal catalyst, corrosive acid, longer
Pd(OAc)2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles
Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175
- simple screw cap vials or schlenks, leading to the desired dimer in good yields. Finally, the synthetic potential of this method for the synthesis of valuable heterocyclic terpenic derivatives was demonstrated with the preparation of several pyran, tetrahydroisobenzofurane and pyrrolidine derivatives by
- (gradient: hexane to hexanes/EtOAc 4:1) and distillation (90 °C, ≈6 mbar), to provide pyran 5 as colorless oil (106.0 mg, 0.64 mmol, 64%). 4-Methyl-2-(3-methylbut-3-en-1-yl)-5,6-dihydro-2H-pyran (5) [42] 1H NMR (400 MHz, CDCl3) δ 5.37–5.31 (m, 1H, H-2), 4.80–4.63 (m, 2H, H-11), 4.04–3.90 (m, 2H, H-2 + H-6a
Conformational impact of structural modifications in 2-fluorocyclohexanone
Beilstein J. Org. Chem. 2017, 13, 1781–1787, doi:10.3762/bjoc.13.172
- study [19], the introduction of an endocyclic oxygen in 2-fluorocyclohexanone to give the 3-fluorodihydro-2H-pyran-4(3H)-one was expected to favor the axial orientation of the fluorine substituent because of the prospective gauche arrangement with the endocyclic oxygen, giving rise to the fluorine
- transition state) or in the ligand assessment to an enzyme binding site. Thus, the replacement of the endocyclic oxygen in 3-fluorodihydro-2H-pyran-4(3H)-one, as well as of the carbonyl oxygen, with other groups, can shift the conformational equilibrium of the resulting molecule towards the equatorial or the
Polyketide stereocontrol: a study in chemical biology
Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39
- reactions present in trans-AT PKSs and certain cis-AT PKSs (for example, pyran synthase domains [19][20], double bond shifting modules [21][22], C-2-hydroxylases [11], etc.) can also have stereochemical consequences, but these will not be treated here as little is known to date about the enzymatic factors
A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring
Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236
- dihydropyridine, hydantoin, imidazole, indole, isoquinoline, isoxazole, oxazole, 4H-pyran, pyrazine, pyridazine, pyridine, pyridinone, pyrimidine, pyrimidone, pyrrole, 3H-quinazolin-4-one, quinoline, 1H-quinolin-4-one, and thiophene. For heterocycles that are composed of a fused aromatic ring, such as
Diastereoselective synthesis of 3,4-dihydro-2H-pyran-4-carboxamides through an unusual regiospecific quasi-hydrolysis of a cyano group
Beilstein J. Org. Chem. 2016, 12, 2093–2098, doi:10.3762/bjoc.12.198
- University, Leninskie gory 1, Moscow, Russia 10.3762/bjoc.12.198 Abstract An efficient diastereoselective approach for the synthesis of functionalized 3,4-dihydro-2H-pyran-4-carboxamides with variable frame was developed based on the reaction of available 4-oxoalkane-1,1,2,2-tetracarbonitriles (adducts of
- TCNE and ketones) with aldehydes in an acidic media. An unusual process of quasi hydrolysis of the cyano group was observed in the course of the described regio- and diastereoselective transformation. Keywords: diastereoselectivity; 3,4-dihydro-2H-pyran-4-carboxamide; nitriles; pyran; quasi-hydrolysis
- influenza caused by influenza A and B viruses contain a 3,4-dihydro-2H-pyran fragment [5]. Moreover, dihydropyrans have been proven to be particularly useful in the preparation of cyclic components of macrocyclic antibiotics [6][7] and as precursors in the synthesis of C-glycosides [8]. Modern and
Rh-Catalyzed reductive Mannich-type reaction and its application towards the synthesis of (±)-ezetimibe
Beilstein J. Org. Chem. 2016, 12, 1608–1615, doi:10.3762/bjoc.12.157
- imine 1B and 5,6-dihydro-2H-pyran-2-one (2h) (Table 2). Unfortunately, the reaction conditions as above gave a complex mixture that did not contain the desired products as shown in Table 2, entry 1. Heating the reaction mixture at 80 °C gave β-aminolactone 4Bh in a very low yield (Table 2, entry 2
- ) was added to the mixture and stirred for 30 min at the same temperature. Subsequently, 5,6-dihydro-2H-pyran-2-one (2, 1.2 equiv) was added to the mixture and then 1.0 M Et2Zn in hexane (3 equiv) was gradually added to the mixture at room temperature, and the mixture was stirred for 24 h. The mixture
Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides
Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148
- precursor and thus particular ring systems [9][10][11]. Most heterocycles in polyketides are formed by specialised PKS domains and tailoring enzymes. These can be active during assembly of the nascent PKS precursor (as for example in the case of pyran/furan formation via oxa-Michael addition, see chapters
- formation of up to two new stereocentres. Its appearance in several polyketide biosynthetic pathways was proposed for a decade based on gene cluster analysis. An in vitro characterisation of responsible catalytic units has however only recently been achieved. Two pyran-forming cyclase domains were
- characterised in the pederin (24) and the ambruticin (28) biosynthetic pathways (Scheme 3 and Scheme 4) [14][15]. PedPS7 is a monofunctional pyran synthase (PS) domain that was predicted to catalyse ring formation from an α,β-unsaturated intermediate in the biosynthesis of the PKS–NRPS hybrid product pederin
Indenopyrans – synthesis and photoluminescence properties
Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81
- Moltech-Anjou, University of Angers, 2 Boulevard Lavoisier 49045 Angers, France 10.3762/bjoc.12.81 Abstract New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be
- heterocycles consisting of fused indene and pyran units. Generally, oxygen-containing heteroaromatic compounds have been encountered as biologically active molecules and display exciting physico-chemical properties. Therefore, these compounds have found many applications in medicinal chemistry and material
- context are benzo[b]indeno-[2,1-e]pyran-10,11-diones, which stimulate the biosynthesis of erythropoietin and are used to treat anemia [10]. Another application includes the use of some amino-spiroindenopyran derivatives as selective sensors for thallium(I) ions in human urine [11]. Pyran-containing
Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes
Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80
- aldehydes in the presence of metal halides to furnish tetrahydro-2H-pyran-2,4-diols in a highly diastereoselective manner, is investigated thoroughly by experiments and computations. The reaction was also successfully implemented on a flow micro reactor system. Keywords: DFT; diastereoselective reaction
- the years [31]. We have already reported a domino aldol–aldol–hemiacetal process that furnishes racemic tetrahydro-2H-pyran-2,4-diols in a highly stereoselective manner (Scheme 1) [30][31][32][33][34][35][36][37]. In this paper, the domino aldol–aldol–hemiacetal reaction involving several metals (Al
- groups, whose probability of allocation at C2 and C6 is 0.5, respectively, appear to be attached to the pyran ring. This can easily be explained by the superposition of two enantiomers which are statistically and isoconformationally incorporated in the crystal lattice. Separation of two enantiomers was
Biosynthesis of α-pyrones
Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56
- -pyrone derivatives for their antimicrobial and cytotoxic properties [2]. The volatile α-pyrone 5-(2,4-dimethylheptyl)-3-methyl-2H-pyran-2-one (7, Figure 1), also named supellapyrone) is used by female brownbanded cockroaches to attract males [13]. It is known that cockroaches use pheromones in many
- -pyran-2-one (47, Figure 10) [52]. Also antitumor activities of α-pyrones had been shown. Thus, pironetin (47, Figure 10) induced apoptosis in a dose- and time-dependent manner, and tubulin assembly was inhibited in vitro [53]. The natural product was isolated from Streptomyces sp. NK10958 [54], and its
- plant pathogenic fungus Hymenoscyphus pseudoalbidus, which inhibited germination of Fraxinus excelsior (European ash) seeds [60]. In contrast, 3-methyl-2H-furo[2,3-c]pyran-2-one, a component of smoke derived from burning plant material, promotes seed germination [61]. Recently, a further regulatory
(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers
Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48
- formation of substituted dihydro-2H-pyran-6-carboxylate 3 (Scheme 4) [16]. It was observed, that by employing PhCOOH as an additive, the yield (%) and the ee (%) increased, in comparison to the use of 4-dimethylaminopyridine (DMAP). A single example was shown leading to 82% yield and an enantiomeric excess
- same nucleophile 81, Wang and his group combined it with β,γ-unsaturated α-ketoesters 87, as the electrophile, catalyzed by bifunctional indane-derived thiourea 88, to produce derivatives of 3,4-dihydro-2H-pyran 89 (Scheme 30) [49]. This reaction sequence involved a Michael reaction, followed by a
- McGarrigle, Galan and co-workers (Scheme 77) [96]. In this reaction the reagent is 2,3,4-trisubstituted dihydro-pyran 247 and the product is the corresponding α-galactopyranose 248. This reaction provides exclusively the α-diastereomer in a yield up to 98%. In 2013, Schmidt and co-workers described the use
Natural products from microbes associated with insects
Beilstein J. Org. Chem. 2016, 12, 314–327, doi:10.3762/bjoc.12.34
- moiety with a pyran ring. A follow-up study via genomic analysis and metabolomic profiles revealed that piperazic acid-containing cyclic depsipeptides are very common in this ecological niche of ant-associated bacteria. Fermentation and purification of metabolite extracts of three ant-associated
Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans
Beilstein J. Org. Chem. 2015, 11, 2435–2443, doi:10.3762/bjoc.11.264
- formation of C–C bonds. Here we describe the asymmetric alkylation of alkylzirconium species to racemic 3,6-dihydro-2H-pyrans. Two systems were examined: 3-chloro-3,6-dihydro-2H-pyran using linear optimization (45–93% ee, up to 33% yield, 5 examples) and 3,6-dihydro-2H-pyran-3-yl diethyl phosphate with the
- obtained by ring-closing methods [29][30]. To extend our previously reported DYKATs beyond all-carbon electrophiles we decided to examine 3-chloro-3,6-dihydro-2H-pyran (2a, Scheme 1b). This was envisaged to be a challenging substrate. The presence of oxygen in the ring would modify the electronics, and
- likely the reactivity, of the starting material. The oxygen lone pairs on 2a could potentially interact with the copper-catalyst or alkyl metal nucleophiles. Results and Discussion We first examined the in situ hydrometallation/AAA of 4-phenyl-1-butene (4) to racemic 3-chloro-3,6-dihydro-2H-pyran (2a
Recent applications of ring-rearrangement metathesis in organic synthesis
Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199
- catalyst 2 to furnish exclusively fused tricyclic systems 83a and 83b in 85% and 61% yields, respectively. Substitution on the cyclohexene system as in compound 82 did not deliver the RRM product (Scheme 16). Pyran systems Donnard and co-workers [21] have accomplished a RRM approach for assembling complex
- required building block 85 has been prepared from compound 84 by allylation with allyl bromide (37). Later, the pyran derivative 85 was treated with catalyst 2 to generate the bicyclic system 86 (73%) (Scheme 17). They also demonstrated a RCM–ROM–RCM cascade using a strain-free allyl heterocycle as useful
- neodysiherbaine via the RRM protocol. To this end, the oxabicyclo[2.2.1]hept-5-ene 256 was subjected to a RRM cascade with catalyst 2 in dichloromethane to produce pyran derivative 257 in 84% yield, which serves as a core structural unit of disyherbaine. Highly functionalized pyran derivative 259 was obtained by
Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach
Beilstein J. Org. Chem. 2015, 11, 1815–1822, doi:10.3762/bjoc.11.197
- aldehyde fragment 6 by asymmetric alkynylation, and form the pyran using an oxa-Michael addition, in a manner reminiscent of that employed by Uenishi and co-workers [34]. Finally, macrocyclisation will be achieved through the well-established strategy of ring-closing metathesis at C8–C9. Results and
Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps
Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147
- product 20 (Scheme 6). Conclusion In summary, we have demonstrated a new approach to intricate C2-symmetric cage bis-spirocyclic pyran derivative 7 through an allyl Grignard reaction and an RCM sequence. The strategy demonstrated here involves an atom economic process. The synthetic sequence demonstrated
A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones
Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137
- naphthoquinones (Figure 1) such as naphtho[2,3-b]furan [5][6][7][8][9][10][11][12][13][14], naphtho-pyran [15][16][17][18], benzo[f]indole [19][20][21][22][23][24], benzo[g]quinolone [25], benzo[b]carbazole [26], naphtho[2,3-b]thiophene [27][28][29][30][31][32][33] and naphtho[2,3-b]]oxazole [34] have been
Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes
Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18
- and pyran derivatives under indirect electrochemical conditions generating selenium or iodonium cations. The reactions proceed in good yields and regioselectivities for the formation of single diastereomers. Keywords: cyclic ethers; cyclisation; 1,4-dienes; electrochemistry; iodonium; selenium
- are in turn potential substrates for the synthesis of functionalised heterocycles. Particularly, we were interested in the synthesis of tetrahydrofuran and pyran derivatives. Those heterocycles are prevalent substructures in many natural compounds, pesticides and drugs with antifungal and
- antibacterial properties [10][11][12][13]. For this purpose, we investigated a protocol for the straight forward synthesis of 1,4-dienols which should be cyclised into the corresponding tetrahydrofuran or pyran derivatives. With our sight set on efficient and atom economic organic reactions electrochemistry
Synthesis of rigid p-terphenyl-linked carbohydrate mimetics
Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182
- from the side of the pyran moiety is assumed since the 1,2-oxazine side is more hindered by the bulky N-benzyl moiety. The secondary hydroxy group of 12a was protected employing t-butyldimethylsilyl trifluoromethanesulfonate and 2,6-lutidine in quantitative yield. The Lewis acid-promoted rearrangement
- spectroscopy that aminopyran 25 is not stable and slowly cyclizes to 24; after two days in CDCl3 solution approximately 20% of aminopyran 25 were converted into 24. This result indicates that the N–O bond cleavage of 12a preceded as expected, but that the produced amino group of the pyran ring seems to be in
Multicomponent reactions in nucleoside chemistry
Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179
- (59a) (X = NH) [92], the N-methyl-4-hydroxy-6-methylpyridin-2(1H)-one (59b) (X = NMe) [92], N-ethyl-4-hydroxy-6-methylpyridin-2(1H)-one (59c) (X = NEt) [92], 4-hydroxy-6-methyl-2H-pyran-2-one (59d) (X = O) [92], or cyclohexane-1,3-dione (60) [93]. The syntheses of derivatives 61 to 64 represent a
C–H-Functionalization logic guides the synthesis of a carbacyclopamine analog
Beilstein J. Org. Chem. 2014, 10, 1564–1569, doi:10.3762/bjoc.10.161
- tetrahydropyranyl ether (3,4-dihydro-2H-pyran, cat. pyridinium para-toluenesulfonate, CH2Cl2, 25 °C, quantiative, inconsequential mixture of diastereoisomers), and the C17 carbonyl group was transformed into its 2-picolylimine (2-picolylamine, cat. para-toluenesulfonic acid, toluene, 111 °C, 92% yield). Subjecting
Multichromophoric sugar for fluorescence photoswitching
Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151
- -dicyanomethylene-2-tert-butyl-6-(p-dialkylaminostyryl)-4H-pyran) [3] with a photochromic diarylethene (DAE) which showed a photoreversible two-way FRET controlled by the state of the photochromic moiety, and 49% quenching of the fluorescence upon UV irradiation [4]. Bifunctional molecules built on two distinct
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