Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• the 1,4-addition of phosphites provides a direct route for accessing chiral phosphonates, there are only a few examples of this reaction [259][260][261][262][263][264]. In 2009, Wang and co-workers reported one of the first catalytic, enantioselective 1,4-addition of phosphites to α,β-unsaturated N

An unusually stable chlorophosphite: What makes BIFOP–Cl so robust against hydrolysis?

• Roberto Blanco Trillo,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2015, 11, 313–322, doi:10.3762/bjoc.11.36

• , in Pd catalysts. Keywords: chirality; hydrolysis; phosphorus; rearrangements; terpenoids; Introduction Phosphorus halides are highly reactive intermediates for the synthesis of phosphites and phosphoramidites [1][2][3][4][5], which are widely used, for example, as ligands in catalysts [6][7][8][9

Synthesis of dinucleoside acylphosphonites by phosphonodiamidite chemistry and investigation of phosphorus epimerization

• William H. Hersh

Beilstein J. Org. Chem. 2015, 11, 184–191, doi:10.3762/bjoc.11.19

• several groups suggests that the inversion barrier is decreased to below 20 kcal/mol [28][29][30]. In order to extend the comparison from phosphines to phosphites, we recently showed that dinucleoside phosphite triesters, like phosphines, epimerize slowly – in this case at 150 °C with an inversion barrier

• differences in rates of diastereomer decomposition. Calculation of acylphosphonite inversion barrier. As described in the Introduction, inversion barriers for phosphines, acylphosphines, and phosphites are known. These were calculated first for validation of the method. The structures of chiral phosphine 18

• , chiral acylphosphine 19, and chiral phosphite 20 (Scheme 4) were each minimized by DFT using Gaussian (see Supporting Information File 1 for details), and the vibrational calculation confirmed a local minimum for each structure. While the phosphites are complicated by multiple local minima, which depend

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• to prevent the coordination of a second phosphorus atom [13][14] or cavity-shaped phosphines [15]. The use of sterically-hindered P(III)-derivatives, notably phosphites [16][17][18][19][20][21], has also proven beneficial in yet another carbon–carbon forming reaction, namely the rhodium-catalysed

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

• study may be regarded as limited, since only dimethyl phosphite was considered in this study. It is indeed well-established that dimethyl phosphite has a singular reactivity when compared to others dialkyl phosphites [6][11]. Moreover, only unsubstituted amine (ammonia) and monosubstituted amine were

• reactions mainly include dialkyl phosphites. It must be noted that the alkyl-chain length can be changed and extended to lipid chains as exemplified in Scheme 17 (oleyl chains). Diaryl phosphite can also be used for AT reactions as illustrated in a recent example published by Gaan et al. (Scheme 21) [70]. O

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• -phosphonates (phosphites) to carbonyl compounds, was performed with oxidized quinine derivatives as the substrates. Homologous aldehydes obtained from the vinyl group reacted in a typical way which led to α-hydroxyphosphonates, first reported compounds containing a direct P–C bond between the quinine carbon

• we planned to envisage a nucleophilic addition of dialkyl phosphites to quinine-based carbonyl compounds and obtain 1-hydroxyalkylphosphonate derivatives (Abramov reaction, phospha-aldol reaction [22][23]). The scope, stereochemistry and side-reactions of the addition are described. Results and

• -aldol) reaction. These carbonyl compounds reacted with dialkyl and diphenyl phosphites producing quinotoxin enol phosphates that resulted from a tandem phosphonate–phosphate rearrangement and an intramolecular piperidine elimination. It can be hypothesized that the driving force of the structural

Synthesis of fluorescent (benzyloxycarbonylamino)(aryl)methylphosphonates

• Michał Górny vel Górniak,
• Anna Czernicka,
• Piotr Młynarz,
• Waldemar Balcerzak and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 741–745, doi:10.3762/bjoc.10.68

• tissues. Thus, their libraries may serve for the construction of diagnostic tools. A similar approach has been recently patented as a mean to differentiate lipases and esterases [15]. The objective of this paper is to evaluate the utility of a popular three component reaction of triaryl phosphites with

• obtained by using the classical three-component amidoalkylation procedure described by Oleksyszyn et al. (Scheme 1) [14]. First, appropriate triaryl phosphites have to be synthesized. They were obtained by refluxing stoichiometric quantities of phosphorus trichloride with the appropriate phenol (molar

• ratio 1:3) in acetonitrile [16][17]. The desired phosphites deposited from acetonitrile as solids or oils and did not require further purification. Corresponding reactions carried out in different solvents (toluene, benzene or diethyl ether in the presence of butyllithium in hexane) or with phosphorus

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• inexpensive phosphites (P(OR)3) have only been applied as phosphine substitutes in one single example: Beal [46] utilized tri-isopropylphosphite in a Mitsunobu condensation of a guanine-derived nucleoside analog with benzylic alcohols providing simplified byproduct separation through improved water solubility

• phosphites (P(OR)3), activated through oxidants such as iodine, have been reported to give the corresponding phosphates in a Michaelis–Arbuzow type reaction [83][84][85] (Scheme 5). In order to improve atom economy and side product separation, we rationalized that in the phosphonium intermediate III

• , respectively (entries 8–9). Whereas OP(OiPr)3 was hydrolyzed in the work up, OP(OPh)3 was not saponified and therefore still remained in the isolated product 13f. However, considering the atom economy these phosphites do not represent an alternative to P(OEt)3. Even the diols rac-12g and 12h with a sterically

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• enantioselective versions of these two cycloadditions was actively pursued by several groups. The electronic similarity between phosphites and phosphoramidites suggested that chiral gold complexes of these highly modular monodentate ligands [65] could be good candidates to promote enantioselective variants of the

• π-acceptor ligands, such as phosphites or phosphoramidites favor the formation of the [4 + 2] adduct of type 15, DFT calculations indicated that the activation barriers for the ring-contraction process leading to these six-membered systems, and the 1,2-H shifts that retain that seven-membered ring

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• solvent. No external base was needed when the alcohol was the nucleophile. However, if the sulfonamide was the nucleophile, an external base such as t-BuOK was required presumably to increase the nucleophilicity of the sulfonamide. The Rueping group trapped the iminium ions using phosphites 76 to produce

• suppressed [65][66]. The reactions were also sensitive to the steric and electronic nature of phosphites. Phosphites are quite acidic; their pKas are similar to alcohols. Less sterically hindered phosphites reacted faster as did more acidic phosphites (e.g., diphenylphosphite). The König group applied the

• amides. Intramolecular interception of iminium ions by sulfonamides. Intramolecular interception of iminium ions by alcohols and sulfonamides. Intermolecular interception of iminium ions by phosphites. Photoredox-catalyzed oxidative phosphonylation by Eosin Y. Conjugated addition of α-amino radicals to

Automated synthesis of sialylated oligosaccharides

• Davide Esposito,
• Mattan Hurevich,
• Bastien Castagner,
• Cheng-Chung Wang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183

• from commercially available Sia (Figure 1b). Compound 6 was converted in a single step into various sialylating agents, such as the N-phenyl trifluoroacetimidoyl glycoside 10, and glycosyl phosphites 8 and 1 as previously described (Table 1) [19][20][21]. Galactal 2 was identified recently as an

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• equation 6 in Scheme 6. For pyridine as the Lewis base the benzhydryl cation affinity (TCA) amounts to TCA(1) = 82.9 kJ/mol at the MP2-5 level of theory. The TCA values of some Lewis bases commonly used in organocatalysis as well as various phosphanes and phosphites are shown in Table 10. In general, TCA

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• shift) in the initially formed cycloheptenyl–gold carbene intermediate XXX (Scheme 28). Thus, the ligand at gold determines the fate of this carbene and hence the formation of the (4 + 3) (50) or (4 + 2) (53) cycloadducts. Based on the electronic similarity between phosphites and phosphoramidites, we

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• ligand on the structure of gold-substituted 3,3-dimethyl allyl cations of type D. Increasing trans σ-donation from the ligand and strongly π-acidic ligands such as phosphites (decreasing back π-donation from gold to C1) led to a longer C1–Au bond and hence a more carbocation-like character for the

• the desired cyclopropanation product 48, but the yield and the diastereoselectivity were highly dependent on the gold ligand. As anticipated from the structural studies, π-acidic phosphites that increase cation-like reactivity gave little or none of the cyclopropanation product 48. Phosphines gave

Unexpected degradation of the bisphosphonate P-C-P bridge under mild conditions

• Petri A. Turhanen and
• Jouko J. Vepsäläinen

Beilstein J. Org. Chem. 2008, 4, No. 7, doi:10.1186/1860-5397-4-7

• (>95% degradation was observed) sodium acetate 6 and phosphites 2–4 (compound 4 can be also called phosphorous acid monosodium salt) as can be seen in Scheme 2. Compounds 2–4 were readily characterized by their P-H chemical shifts and characteristic 1JHP coupling constants (ca. 600 Hz). In the 31P NMR

• spectrum, there were three different monophosphorus components confirmed to be compounds 2–4. Two moles of acetate 6 were detected compared to one mole of the total amount of phosphites 2–4 which was the expected result. Interestingly, the decomposition mixture of 1a contained not only monoethyl phosphite

• selectively degraded to the phosphite 3 and acetyl phosphonate 7 when 5 equiv of triethylamine was used in H2O (see Scheme 1). Dialkyl acetylphosphonates and dialkyl phosphites are common starting materials for the synthesis of tetraalkyl esters of HEBPA [26][27], but this is the first time when the “reverse

Pd-catalysed [3 + 3] annelations in the stereoselective synthesis of indolizidines

• Olivier Y. Provoost,
• Andrew J. Hazelwood and
• Joseph P. A. Harrity

Beilstein J. Org. Chem. 2007, 3, No. 8, doi:10.1186/1860-5397-3-8

• phosphites have been reported using Grignard reagents [14]. In addition, 31P NMR studies showed that the addition of 1 equivalent of nBuLi to P(OPri)3 gave a mixture of P(OPri)3 and PBun3 after 15 minutes (See Supporting Information File 1 for details). Interestingly however, we have found PBun3 to be

Study of thioglycosylation in ionic liquids

• Jianguo Zhang and
• Arthur Ragauskas

Beilstein J. Org. Chem. 2006, 2, No. 12, doi:10.1186/1860-5397-2-12

• ionic liquid employed. The reactivity of glycosyl trichloroacetimidates and diethyl phosphites with alcohols in the presence and absence of lewis acids has been also recently been reported with several ionic liquids, including [bmim]PF6 and 1-n-hexyl-3-methylimidazolium trifluoromethanesulfonimidide.[8

A superior P-H phosphonite: Asymmetric allylic substitutions with fenchol- based palladium catalysts

• Bernd Goldfuss,
• Thomas Löschmann,
• Tina Kop-Weiershausen,
• Jörg Neudörfl and
• Frank Rominger

Beilstein J. Org. Chem. 2006, 2, No. 7, doi:10.1186/1860-5397-2-7

• product by employing electron withdrawing substituents on the P-donor atoms in P, N-oxazoline ligands[5] (Scheme 2) [6]. Such phosphites were thought to favor a more SN1-like addition at the substituted, allylic C-atom. High regio- and enantioselectivities were also achieved with biphenylphosphites by

• , reflecting the effect of steric demanding and electron donating pyridine groups on enantioselectivity. The surprisingly stable halogen phosphites BIFOP-Cl and BIFOP-Br yield even higher enantioselectivities (39% and 37% ee) than the corresponding phosphite BIFOP-OPh or the phosphoramidite BIFOP-NEt2 (10% and

• 29% ee, Table 1). To our knowledge, this is the first successful application of halogen phosphites as ligands in enantioselective catalysis [26]. The highest enantioselectivity however is achieved with the P-H phosphonite BIFOP-H (65% ee, Table 1). As in copper-catalyzed 1,4-additions of diethylzinc

Synthesis of phosphorothioates using thiophosphate salts

• Babak Kaboudin and
• Fatemeh Farjadian

Beilstein J. Org. Chem. 2006, 2, No. 4, doi:10.1186/1860-5397-2-4

• phosphorothioates has received little attention. The following methods, not generally applicable, have been reported in the literature: (i) reaction of dialkyl phosphites with sulfenyl chlorides,[13] sulfenyl cyanides,[14] thiosulfonates,[15][16] disulfides,[17] and sulfur, [18][19][20][21] (ii) condensation of

New modification of the Perkow reaction: halocarboxylate anions as leaving groups in 3-acyloxyquinoline- 2,4(1H,3H)-dione compounds

• Oldřich Paleta,
• Karel Pomeisl,
• Stanislav Kafka,
• Antonín Klásek and
• Vladislav Kubelka

Beilstein J. Org. Chem. 2005, 1, No. 17, doi:10.1186/1860-5397-1-17

• out[3] (product 2) via the intramolecular Wittig synthesis using a bromoacetyl derivative of the starting 3-hydroxyquinolinediones (1, Scheme 1). Unlike haloalkanes and halocycloalkanes that undergo nucleophilic substitution reaction with trialkyl phosphites to afford the corresponding phosphonates

• according to the Michaelis-Arbuzov reaction,[4] the α-halocarbonyl compounds react with triethylphosphite to form enol phosphites 3 as a product of the Perkow reaction (Scheme 2). [5] The reaction is otherwise known to take place in halogenated ketones, diketones, aldehydes and also in some halogenoesters

• formation of product 9 is depicted in Scheme 5. An analogous mechanism featuring fluoride anion as a leaving group was proposed previously for the reaction of perfluorinated aliphatic ketones with trialkyl phosphites. [7] The products 8 and 9 were obtained in isolated yields of 18–68% and 11–38% (Table 1

An exceptional P-H phosphonite: Biphenyl- 2,2'-bisfenchylchlorophosphite and derived ligands (BIFOPs) in enantioselective copper- catalyzed 1,4-additions

• T. Kop-Weiershausen,
• J. Lex,
• J.-M. Neudörfl and
• B. Goldfuss

Beilstein J. Org. Chem. 2005, 1, No. 6, doi:10.1186/1860-5397-1-6

• -catalyzed 1,4-additions of ZnEt2 to 2-cyclohexen-1-one, this P-H phosphonite (yielding 65% ee) exceeds even the corresponding phosphite and phosphoramidite. Keywords: phosphorus ligands; chirality; biaryls; asymmetric conjugate additions; phosphoramidites; phosphites; phosphonites; X-ray analyses

• ][13][14][15][16][17][18] Such asymmetric conjugate additions of diethylzinc to enones are often highly enantioselective, especially with phosphoramidites (amidophosphites) and phosphites. [2][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] These chiral

• phosphites are highly reactive chlorophosphites. [48][49][50][51] These intermediates are converted usually in situ with amines or alcohols to the modular, enantiopure ligands (Scheme 2). [2][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. Modular fencholates were

Mixtures of monodentate P-ligands as a means to control the diastereoselectivity in Rh-catalyzed hydrogenation of chiral alkenes

• Manfred T. Reetz and
• Hongchao Guo

Beilstein J. Org. Chem. 2005, 1, No. 3, doi:10.1186/1860-5397-1-3

• involves the use of additives, catalyst poisons or catalyst activators.[10][11] Based on the discovery that monodentate BINOL-derived phosphites,[12][13] phosphonites[14][15] and phosphoramidites [16][17][18] are excellent ligands in enantioselective Rh-catalyzed olefin-hydrogenation, we proposed in 2003 a

• (Scheme 1). If the hetero-combination dominates due to enhanced activity and enantioselectivity, a superior catalytic profile can be expected. A mechanistic study of Rh-catalyzed olefin-hydrogenation using BINOL-derived monodentate phosphites (homo-combination) has shown that two such ligands are bound to

• the metal in the transition state of the reaction,[13] and it is certain that in the case of mixtures analogous species are involved.[19][20] This new strategy was first employed in Rh-catalyzed olefin-hydrogenation using mixtures of BINOL-derived phosphites and phosphonites[19][20] and was then