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Search for "phosphite" in Full Text gives 114 result(s) in Beilstein Journal of Organic Chemistry.
Pyrrolidine nucleotide analogs with a tunable conformation
Beilstein J. Org. Chem. 2014, 10, 1967–1980, doi:10.3762/bjoc.10.205
- derivatives 7–10 were prepared from pyrrolidine azanucleosides 15a–d [5][15] via a Mannich-type reaction with diisopropyl phosphite and aqueous formaldehyde at elevated temperature in good yields (Scheme 1). The obtained diisopropyl esters 17a–d were deprotected by treatment with trimethylsilyl bromide in
Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules
Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195
- phosphonamides through alkylation of bicyclic phosphite anions [69][70][71]. Thus, condensation of diamine 58 with phosphorus trichloride followed by hydrolysis of the formed 2-chloro-1,3,2-diazaphospholidine with one equivalent of water gave phosphorus acid diamide 68. The latter could be deprotonated with LDA
Structure/affinity studies in the bicyclo-DNA series: Synthesis and properties of oligonucleotides containing bcen-T and iso-tricyclo-T nucleosides
Beilstein J. Org. Chem. 2014, 10, 1840–1847, doi:10.3762/bjoc.10.194
- the modified residues, most likely on the level of the iodinated phosphite intermediate [35], leading to the formation of an allylic carbocation in the bcen-T unit and 5’-phosphorylated DNA fragment (Scheme 3). The synthesis of oligonucleotides using building block 10 proved to be even more difficult
Multicomponent reactions in nucleoside chemistry
Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179
- reaction (Scheme 11) proceeds in a three-component system involving a carbonyl compound (aldehyde or ketone), amine, and a hydrophosphoryl compound (mainly alkyl/aryl phosphite) [74][75]. The reaction products, commonly termed as α-aminophoshonates, display properties of industrial and/or medical interest
- phosphite were carried out under solvent-free conditions at 60 °C (for 14) or at 80 °C (for 27). Products 28 and 29 were obtained in good to excellent yields as 1:1 diastereoisomeric mixtures arising from the generation of a stereogenic center at the aminophosphonate chain. The mixtures were not separated
Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction
Beilstein J. Org. Chem. 2014, 10, 1536–1548, doi:10.3762/bjoc.10.158
- substrates [59]. A highly efficient asymmetric arylation in the presence of sugar-derived phosphite-oxazoline ligands was reported by Diéguez and Pàmies [47][48]. PHOX ligands are very appealing due to their high catalytic potential and modular design, which permits easy preparation of a series of analogues
Synthesis of 1-[bis(trifluoromethyl)phosphine]-1’-oxazolinylferrocene ligands and their application in regio- and enantioselective Pd-catalyzed allylic alkylation of monosubstituted allyl substrates
Beilstein J. Org. Chem. 2014, 10, 1261–1266, doi:10.3762/bjoc.10.126
- branched monosubstituted allyl acetate favoring the branched products. However, linear products were favored when the linear allyl substrates were employed [23][24]. The chiral oxazoline–phosphite ligands introduced by Pfaltz and coworkers proved to be highly efficient for regio- and enantiocontrol in the
Atherton–Todd reaction: mechanism, scope and applications
Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117
- Atherton–Todd (AT) reaction was applied for the synthesis of phosphoramidates by reacting dialkyl phosphite with a primary amine in the presence of carbon tetrachloride. These reaction conditions were subsequently modified with the aim to optimize them and the reaction was extended to different
- by chance. Indeed, these authors attempted to purify a solution of dibenzyl phosphite in carbon tetrachloride by its treatment with an aqueous ammonia solution. They observed the formation of a precipitate that was identified as O,O-dibenzyl phosphoramidate. However, no reaction occurred when
- dibenzyl phosphite was mixed alone with carbon tetrachloride, whereas an exothermal reaction occurred if gaseous ammonia was passed through this solution or if this solution was shaken with an aqueous ammonia solution, with chloroform and ammonium chloride as byproducts. The replacement of ammonia with
Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination
Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85
- skeleton and a phosphorus atom. For the C9 ketones a phosphonate–phosphate rearrangement, associated with a tandem elimination of the piperidine fragment, was evidenced. Keywords: carbonyl derivatives; dialkyl phosphite addition; organophosporus; phosphonate–phosphate rearrangement; quinine oxidation
- % yield. The obtained aldehydes 4, 6, and 8 were reacted with 1.1 equiv of diethyl phosphite. The presence of the tertiary amino group of quinuclidine was expected to be a sufficient catalytic base for the addition reaction, and furthermore to induce a diastereoselectivity. However, the expected
- was treated with diethyl phosphite and heated in toluene at 50 °C for a week with addition of a catalytic amount of triethylamine (Scheme 4). The reaction mixture was purified by column chromatography. Formation of four diastereomeric compounds, derivatives of epiquinidine (8R,9R), quinidine (8R,9S
Synthesis of fluorescent (benzyloxycarbonylamino)(aryl)methylphosphonates
Beilstein J. Org. Chem. 2014, 10, 741–745, doi:10.3762/bjoc.10.68
- (Scheme 1) with good yields (59–86%). Unfortunately, the reaction of phosphite obtained from 7-hydroxycoumarine failed, since it appeared to be unstable upon harsh reaction conditions and underwent decomposition as seen by 31P NMR. Therefore, we have decided to apply a more delicate procedure described
- recently by Goldeman and Soroka [21]. According to this procedure the reaction was carried out in dry chloroform in the presence of catalytic amounts of tetrafluoroboric acid. Unfortunately, tri(7-hydroxycoumaric) phosphite also underwent decomposition under these conditions. The diaryl esters 2 exhibit
Silver and gold-catalyzed multicomponent reactions
Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46
- Scheme 21). This can be a simple nucleophile (indole 30, imidazole 31, diethyl phosphite (32), Scheme 20) [53][54][55] or can be generated in situ (enolate 33, enamine 34, Scheme 21) [56][57] from a suitable precursor and a second catalyst (dual activation strategy) affording 1,3-disubstituted-1,2
- electron-rich and electron-poor anilines are suitable partners for these reactions, whereas alkylamines and benzylamine gave worse results. Moreover, the third partner (Nu in Scheme 19) is limited to one substrate as in the reaction employing diethyl phosphite (32). Indoles 30 and imidazoles 31 can bear
Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration
Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35
- the step-economic and stereodivergent synthesis of trans- and cis-2-substituted 3-piperidinols B, we want to report the development of this sequence in more detail with a focus on the phosphite-mediated cyclodehydration. Additionally, the synthesis of a side chain functionalized piperidinol derived
- hours of reflux, see Table 2, entry 3). Chromatographic purification of the crude piperidinols 11a–d, which were already isolated in 85–90% purity (from the phosphite cyclodehydration), was best achieved with halogen free iPrOH/Et3N/hexane eluent mixtures (ratio 0.8–3:2–4:100 depending on the polarity
- effect we chose a ratio of Et3N/CH2Cl2 1:2 as standard conditions for the phosphite mediated cyclodehydration. Typically, 5 to 6 equivalents of Et3N resulting in a reasonable concentration of the substrates 11 and 12 (see Table 3) of 0.4–0.5 mol/L (in Et3N/CH2Cl2) were sufficient enough to guarantee
New developments in gold-catalyzed manipulation of inactivated alkenes
Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294
- were accessed by intramolecular addition in excellent yields (Scheme 8b). The combined use of more electrophilic phosphite-gold complexes [41][42] and enabling techniques such as microwave irradiation [43] led to consistent improvement in efficiency of the catalytic system. In particular when (Ph3O
Gold(I)-catalyzed enantioselective cycloaddition reactions
Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264
- allyl cation to the diene. Curiously, by using a gold(I) catalyst bearing a π-acceptor phosphite ligand, such as Au10/AgSbF6, allenedienes disubstituted at the distal position of the allene lead to products formally arising from a [4 + 2] cycloaddition process (Scheme 8, b) [59][60]. Several
- substituents at the Binol ortho-positions (Au11, Scheme 9) [60]. Independently, Toste and co-workers reported that the related phosphoramidite–gold complex Au12, and the chiral gold catalyst Au13, derived from a C3-symmetric phosphite [66], were also able to induce excellent enantioselectivities in these [4
- include a phosphite–gold complex Au10 and a biaryldi-tert-butylphosphine–gold complex (Au3) [74][75][76]. More recently, González and co-workers accomplished the enantioselective version of these annulations between sulfonyl allenamides and vinylarenes, providing a straightforward entry into optically
Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives
Beilstein J. Org. Chem. 2013, 9, 2120–2128, doi:10.3762/bjoc.9.249
- competition with a direct Friedel–Crafts-type cyclization reaction yielding 3. In previous work dealing with the cyclization of N-(3-iodoprop-2-ynyl)-N-tosylanilines to give related 1,2-dihydroquinolines (Scheme 4A, X = NTs) [43], we documented for a phosphite-based gold-catalyst, which render a more
Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization
Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181
- Erba), ethyl acetate (EtOAc, Carlo Erba), triethyl phosphite (P(O)(OEt)3, Aldrich, 99+% ), and tert-butylbenzene (t-BuPh, Aldrich, 99%) were used as received. The 2-methyl-2-(N-tert-butyl-N-(1-diethoxyphosphoryl-2,2-dimethylpropyl)aminoxy)-propionic acid alkoxyamine (BlocBuilder MA, BB) was kindly
Methylidynetrisphosphonates: Promising C1 building block for the design of phosphate mimetics
Beilstein J. Org. Chem. 2013, 9, 991–1001, doi:10.3762/bjoc.9.114
- ]. Review Preparation of methylidynetrisphosphonates Synthesis via a Michaelis–Arbuzov reaction Phosphonate esters are often prepared through Michaelis–Arbuzov reaction of a trialkyl phosphite with an alkyl halide [9]. However, contrary to the early patent claims, trisphosphonate esters cannot be derived
- from simple trihalomethyl derivatives [10][11][12]. Indeed, chloroform and bromoform do not react with triethyl phosphite even under harsh conditions [11]. In addition, no reaction occurred between benzotrichloride (PhCCl3) and triethyl phosphite at a temperature below 150 °C. The CuCl-catalyzed
- reaction of PhCCl3 and (EtO)3P at 120–140 °C produced 1,2-diphenyl-1,1,2,2-tetrachloroethane [13]. The early work reported that the trisphosphonate PhC(PO3Et2)3 was formed from triethyl phosphite and dibenzoyl peroxide when reagents were boiled under reflux in chloroform, but proof of the trisphosphonate
An improved synthesis of a fluorophosphonate–polyethylene glycol–biotin probe and its use against competitive substrates
Beilstein J. Org. Chem. 2013, 9, 89–96, doi:10.3762/bjoc.9.12
- combined 90% yield. The phosphonate moiety was installed under standard Arbuzov conditions by heating 4b under reflux in neat triethyl phosphite for 1 h to provide novel intermediate 5 in 92% yield following purification by column chromatography. Clean removal of the benzyl protecting group under standard
- -phenyl-2,5,8,11-tetraoxatridecan-13-yl)phosphonate (5): Iodobenzyl polyether 4b (17.44 g, 44.23 mmol) and triethyl phosphite (32 mL, 183.9 mmol) were mixed in an oven-dried round-bottom flask and heated under reflux for 1 h. Excess triethyl phosphite was removed under vacuum and the reaction mixture was
Automated synthesis of sialylated oligosaccharides
Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183
- and 3). The glycosylation of galactal 2 with phosphite 1, which we described in the supporting information of [5], was further optimized. In particular, elevating the reaction temperature proved beneficial and disaccharide 9 was isolated in higher overall yield, albeit with a slight decrease in
Synthesis of fluoranthenes by hydroarylation of alkynes catalyzed by gold(I) or gallium trichloride
Beilstein J. Org. Chem. 2011, 7, 1520–1525, doi:10.3762/bjoc.7.178
- demonstrated to be amongst the best catalysts in many gold(I)-catalyzed cyclizations [6][58]. No reaction was observed with complex 5 after heating for 5 min at 70 °C in CH2Cl2 under microwave irradiation (Table 1, entry 1), whereas the more electrophilic 6, bearing a less donating phosphite ligand, led almost
- -tetrahydrofluoranthene, and 8a, the crude mixtures were treated with excess DDQ in toluene under reflux to provide pure 8a. No reaction or decomposition was observed when the reaction was carried out with gold(I) complex 5 (Table 2, entries 1 and 2). In contrast, the more electrophilic gold(I) complex 6 with phosphite
- Highly electrophilic gold(I) catalyst 6 with a bulky phosphite ligand competes with GaCl3 as the catalyst of choice for the hydroarylation of alkynes. The synthetic potential of this catalyst is illustrated by the synthesis of functionalized triarylated decacyclenes in which three C–C bonds are formed
Combination of gold catalysis and Selectfluor for the synthesis of fluorinated nitrogen heterocycles
Beilstein J. Org. Chem. 2011, 7, 1379–1386, doi:10.3762/bjoc.7.162
- conditions, the formation of 5a was not detected (Table 1, entry 4). Gold(I) phosphite catalysts gave 3a and 4a in low yields (Table 1, entries 6 and 7). A similar result was observed with tri(tert-butyl)phosphine gold(I) chloride (Table 1, entry 8). The dinuclear complex, dppm(AuCl)2, led to 3a and 5a in a
The Eschenmoser coupling reaction under continuous-flow conditions
Beilstein J. Org. Chem. 2011, 7, 1164–1172, doi:10.3762/bjoc.7.135
- ; triisopropyl phosphite; Introduction The Eschenmoser coupling [1][2] is a reaction method that yields β-enaminocarbonyl derivatives of type 4 by the elimination of sulfur (sulfide contraction) from an episulfide intermediate (Scheme 1). The reaction was described for the first time by Knott in 1955 [3] and
- agent, the mechanism of extraction via intermediate ionic states also seems plausible. Nevertheless, the Eschenmoser coupling reaction requires the addition of a base and a thiophilic agent in the most cases. Here, triphenylphosphine- or trialkyl-phosphite-derivatives are usually employed to promote the
Recent developments in gold-catalyzed cycloaddition reactions
Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124
- and 3' positions of the binaphthol moiety (Au9, Scheme 29) [102]. Almost simultaneously, the group of Toste reported that related phosphoramidite–gold complexes, such as Au10, and the chiral gold catalyst Au11 [104], derived from a C3-symmetric phosphite ligand previously developed by Reetz and
Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization
Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106
- cyclization product was obtained only in 64% yield (Table 1, entry 11). The low yield relative to the conversion value is probably due to oligomerization and/or product decomposition as suggested by TLC and 1H NMR analysis of the crude mixture. A phosphite ligand P(OPh)3, which is comparable to
Recent advances in the gold-catalyzed additions to C–C multiple bonds
Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103
- catalytic amount of phosphite–gold(I) pre-catalyst and a silver additive. Notably, the addition is regioselective for the allene terminus, and generates (E)-allylation products 202. The direct C–H functionalization of indoles or pyrroles is an efficient method for the introduction of vinyl and aryl groups
Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles
Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89
- increase in the ratio of 4a (Table 1, entry 7). Finally, the use of the bulky phosphite ligand tris(2,4-di-t-butylphenyl)phosphite, gave rise to a 1.5/1 ratio of 3a/4a (Table 1, entry 8) [32]. Once tris(2,4-di-t-butylphenyl)phosphite was selected as the best ligand to favor the desired tandem process, the
- responsible for the selectivity switch in favor of the Nazarov product. Nevertheless, the beneficial effect of the bulky phosphite ligand is also significant factor with regards to both reactivity and selectivity. To examine further the scope of this switch of selectivity in favor of the Nazarov pathway in
- as catalyst (Scheme 3). Interestingly, under the new conditions developed herein, i.e., treatment with a cationic phosphite–gold complex in toluene, the reaction of 1j afforded a ca. 3.5/1 mixture of 3j/4j, whereas 1k gave rise to a ca. 1.6/1 mixture of 3k/4k (Scheme 3). These results again show that
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