Phosphinate-containing heterocycles: A mini-review

• Olivier Berger and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2014, 10, 732–740, doi:10.3762/bjoc.10.67

• developed by Pirat and coworkers. Scheme 24 shows the synthesis of a H-phosphinate intermediate 59 in 65% yield via the reaction between the imine 57 of the racemic 1,2-diphenylethanolamine with benzaldehyde and methyl phosphinate (58) followed by the cyclization through a base catalyzed transesterification

• synthesized in two steps at room temperature, first, by a nucleophilic attack of methyl hypophosphite on oxazolidine 60 followed by an intramolecular cyclization, this time without base catalyzed transesterification. The authors explained this difference of reactivity by the Thorpe–Ingold effect [38]. Indeed

• (trimethylsiloxy)phosphine. Diastereoselective ring-closing metathesis. 2-Ketophosphonate/benzene annulation. Tandem Kabachnik–Fields/transesterification reaction. Tandem Kabachnik–Fields/transesterification reaction with oxazolidine. Acknowledgements This material is based in part upon work supported by the

Synthesis of complex intermediates for the study of a dehydratase from borrelidin biosynthesis

• Frank Hahn,
• Nadine Kandziora,
• Steffen Friedrich and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2014, 10, 634–640, doi:10.3762/bjoc.10.55

• conditions. As the presence of a methyl ester would prevent the selective introduction of one thioester into 5a by saponification–thioesterification, we planned transesterification from a suitably activated carboxylic acid derivative 8. Alternatively, direct introduction into 11 with appropriate SNAc

• thioester building blocks was planned for the synthesis of 6a and 6b. Starting from aldehyde 11, a common precursor for all molecules required in this study, aldol reaction and following transesterification should lead to thioester 8. The bismethyl esters 7a and 7b as well as the SNAc thioesters 6a and 6b

• 17a and 17b with HSNAc and triethylamine in DMF, they underwent clean transesterification furnishing SNAc thioesters 18a and 18b in 70% combined yield [20] (Scheme 3). With the mixture of 18a and 18b in hand, we turned to the mild removal of the protection groups. For TBS cleavage, we focused on

The regulation and biosynthesis of antimycins

• Ryan F. Seipke and
• Matthew I. Hutchings

Beilstein J. Org. Chem. 2013, 9, 2556–2563, doi:10.3762/bjoc.9.290

• acyltransferase, which catalyses a transesterification reaction resulting in the formation of a C-8 acyloxyl moiety and is responsible for generating the chemical diversity at R1 (Figure 1). AntB likely performs this reaction after assembly of the dilactone core, as wild-type levels of biosynthetic intermediates

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• the mutifunctionalized product 19 as a single isomer. The stereochemistry of 19 could be presumably assigned by considering the 1,5-hydrogen shift mechanism (entry 5) [17]. The reaction of alkene 10 bearing a methyl ester moiety gave γ-lactone 20 by intramolecular transesterification with a tertiary

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• the TBS group were removed first, the free hydroxy group would undergo elimination, it seemed likely that both deprotections would proceed at ambient temperature, which might circumvent this issue. Transesterification of methyl ester 45 to TMSE ester 64 proceeded in good yield, and following an

1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

• Astrid Hoppe,
• Faten Sadaka,
• Claire-Hélène Brachais,
• Gilles Boni,
• Jean-Pierre Couvercelle and
• Laurent Plasseraud

Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73

• carbon dioxide transfer in the formation of ketoacetates [46][47] and carboxylation of epoxides [48]. Some of us have recently reported a green application of BMIM-2-CO2, highlighting its efficiency for the conversion of raw glycerol to glycerol carbonate by transesterification [49]. More recently, this

• concept was extended to the synthesis of aliphatic polycarbonates, involving the transesterification of DMC with linear alkane diols under solvent-free conditions, and based on a two-step polymerization process [50]. The high reactivity of imidazolium-2-carboxylates can be explained by their facile

• theoretical and experimental values of Mn, despite a complete conversion. These deviations, which are significant in some cases, can be explained by a backbiting process and the involvement of redistribution reactions (inter- and intra-transesterification reactions) [55]. In all cases, the values of both

Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids

• Paweł Borowiecki,
• Małgorzata Milner-Krawczyk and
• Jan Plenkiewicz

Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56

• -propylene oxide with imidazole or 1,2,4-triazole. Lipase-catalyzed transesterification of alcohols with vinyl acetate resulted in kinetic enantiomers resolution. Separated (S)-enantiomers of (+)-1-(1H-imidazol-1-yl)propan-2-ol and (+)-1-(1H-1,2,4-triazol-1-yl)propan-2-ol were quaternized with alkyl bromides

• ). Next, these compounds were used as a new type of substrate in lipase-catalyzed transesterification, yielding both enantiomers with good optical purity. The syntheses of the secondary alcohols (±)-3a and (±)-3b were accomplished by the addition of imidazole (2a) or 1,2,4-triazole (2b) to 1,2-propylene

• ) and two immobilized enzymes (Novozym SP 435, Amano PS-IM), were chosen for the transesterification studies. The screenings were performed with a 5-fold molar excess of vinyl acetate as an irreversible acyl donor at ambient temperature. The selection of a proper solvent is a significant factor in

From bead to flask: Synthesis of a complex β-amido-amide for probe-development studies

• Kevin S. Martin,
• Cristian Soldi,
• Kellan N. Candee,
• Hiromi I. Wettersten,
• Robert H. Weiss and
• Jared T. Shaw

Beilstein J. Org. Chem. 2013, 9, 260–264, doi:10.3762/bjoc.9.31

• this reaction was significantly lower, less than 50%, compared to the reaction to produce 14, and we observed some transesterification of the methyl ester with butanol to produce a mixture of 27 and the butyl ester of 27 as the major products (not shown). We thus turned to using Oxone, and

Alternaric acid: formal synthesis and related studies

• Michael C. Slade and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2013, 9, 166–172, doi:10.3762/bjoc.9.19

• selectivity in 65% yield (Scheme 3). Ichihara’s aldehyde intermediate could be intercepted in three additional steps, in high overall yield. Simultaneous cleavage of the silyl ether and transesterification from the tert-butyl to the methyl ester in 6 was effected by warming in acidic methanol. Subsequent

Organocatalytic asymmetric allylic amination of Morita–Baylis–Hillman carbonates of isatins

• Hang Zhang,
• Shan-Jun Zhang,
• Qing-Qing Zhou,
• Lin Dong and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2012, 8, 1241–1245, doi:10.3762/bjoc.8.139

• realized with Zn powder in acetic acid to produce compound 5, albeit in modest yield [34][35], whose absolute configuration has been determined by X-ray analysis [36]. The removal of the O-TBS unit proceeded efficiently in the presence of hydrofluoric acid, and an intramolecular transesterification process

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• of the triazine ring, thereby preventing the desired cycloaddition. In addition to the amide linkage of the alkyne dienophiles, transesterification of 8a with alkynyl alcohols led to tethered alkynyl esters as cycloaddition precursors 17a and 17b in good yields (Scheme 9). Various catalysts for the

• transesterification reaction were screened. Boronic acid [91] and indium(III) iodide [92] yielded no transesterification product with propargyl alcohol, while Ti(OiPr)4 [93] gave only a trace of the desired product, with mostly detosylation resulting. Otera’s catalyst [94] proved to be optimal, giving cycloaddition

• triazines. One-pot amidation/cycloaddition of triazine ester 8a. Amidation/cycloaddition forming α-carbolines 14. Intramolecular hydrogen bonding prevents IEDDA cycloaddition of 14b. Preparation of unprotected triazine 15, and its lack of reactivity in cycloadditions. Transesterification and subsequent

Synthesis and antiviral activities of spacer-linked 1-thioglucuronide analogues of glycyrrhizin

• Christian Stanetty,
• Andrea Wolkerstorfer,
• Hassan Amer,
• Andreas Hofinger,
• Ulrich Jordis,
• Dirk Claßen-Houben and
• Paul Kosma

Beilstein J. Org. Chem. 2012, 8, 705–711, doi:10.3762/bjoc.8.79

• diphenylmethyl ester group with TFA/anisole (as carbocation scavenger), giving the monoacid derivatives 10 and 11 in 75% and 89% yield, respectively. Subsequent transesterification of 10 and 11 with methanolic NaOMe afforded the deacetylated methyl ester glucuronide derivatives 12 and 14, respectively, which

Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

• Michel Chiarucci,
• Mirko Locritani,
• Gianpiero Cera and
• Marco Bandini

Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139

• confirms the allylic SN1 mechanism for the present methodology [44]. The high chemoselectivity guaranteed by the gold catalysts is worthy of note, as it channels the reaction toward the allylic alkylation mechanism without any contamination deriving from transesterification reactions. This evidence is

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• outcome was obtained using NIS/TfOH activation of thioglycoside donor 17 to furnish disaccharide 26 in 72% yield. Selective deacetylation of 26 was achieved by acidic transesterification using 3% AcCl in MeOH/CH2Cl2 to give the secondary alcohol 27 in 73% yield. Mannosylation of 27 using donor 21 under

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• ADMET polymerizations were studied in detail. The isomerization reactions were investigated by degradation of the prepared polyesters via transesterification with methanol, yielding diesters. These diesters, representing the repeat units of the polyesters, were then quantified by GC-MS. Keywords: ADMET

• room temperature. The crude product was purified by precipitation into cold methanol. Final polymer molecular weights were determined after precipitation with the above mentioned GPC system. Transesterification of the obtained polymers (P1-P26) and GC-MS analysis The respective polymer (30 mg), excess

Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine

• Lisa K. Thalén and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2010, 6, 823–829, doi:10.3762/bjoc.6.97

• reaction was observed (Table 2, entries 2 and 3, respectively) indicating that the racemization was slower than the transesterification at these catalyst loadings. An increase in the selectivity was observed when the amount of acyl donor was decreased, however this also coincided with deceleration of the

Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride

• Subrata Kumar Chaudhuri,
• Manabendra Saha,
• Amit Saha and
• Sanjay Bhar

Beilstein J. Org. Chem. 2010, 6, 748–755, doi:10.3762/bjoc.6.94

• chemoselective reduction of the oxo-group, occasionally with subsequent transesterification and the formation of the alkoxy-modified β-hydroxyesters. γ-Oxoesters react chemoselectively with sodium borohydride to produce the corresponding γ-hydroxyesters [1][2][17][23][24][25][26][27] (sometimes in the form of γ

Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length

• Florian K. Wolf,
• Anna M. Fischer and
• Holger Frey

Beilstein J. Org. Chem. 2010, 6, No. 67, doi:10.3762/bjoc.6.67

• range of 1.3–1.7 for the series of star polymers prepared, which is moderate. These values can be explained by the non-monodisperse multifunctional initiator (PDI: 1.9–2.0), although transesterification/cyclization reactions during the synthesis cannot be completely excluded. A detailed account of the

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al₂O₃ under inspection

• Franziska Bernhardt,
• Ronald Trotzki,
• Tony Szuppa,
• Achim Stolle and
• Bernd Ondruschka

Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7

• stoichiometric or catalytic reagent: transesterification of vegetable oils [27], hydrolysis reactions [29], O-methylation of phenol [62], and Michael reactions [63]. In conclusion, it appears that a KF content of 30–40 wt % is sufficient for a mechanochemically initiated conversion of 1 and 2 yielding 3

N-acylation of ethanolamine using lipase: a chemoselective catalyst

• Mazaahir Kidwai,
• Roona Poddar and
• Poonam Mothsra

Beilstein J. Org. Chem. 2009, 5, No. 10, doi:10.3762/bjoc.5.10

• (triacyl glycerol hydrolases EC 3.1.1.3) catalyze hydrolysis, esterification, transesterification, thioesterification, amidation, epoxidation etc. [5][6][7][8][9][10]. The use of immobilized lipases is on the rise, as these work well with non-aqueous media [11]. Apart from the convenient handling, these

Phase- vanishing halolactonization of neat substrates

• Nicole Windmon and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2008, 4, No. 29, doi:10.3762/bjoc.4.29

• -dibromopentanoate (4) (Scheme 2). Apparently, 4,5-dibromopentanoic acid underwent hydrogen bromide-catalyzed transesterification with ethyl acetate. In a control experiment, 4-pentenoic acid was transesterified by dissolving it in ethyl acetate and adding a catalytic amount of HBr in acetic acid. The best results

Stereoselective synthesis of (2S,3S,4Z)-4-fluoro- 1,3-dihydroxy- 2-(octadecanoylamino)octadec- 4-ene, [(Z)-4-fluoroceramide], and its phase behavior at the air/water interface

• Gergana S. Nikolova and
• Günter Haufe

Beilstein J. Org. Chem. 2008, 4, No. 12, doi:10.3762/bjoc.4.12

• provided the desired tert-butyl imino acid ester 5 as a mixture with the ethyl imino acid ester 6 (formed due to a partial transesterification of 4 with the titanium reagent) and four non-identified compounds (among them most likely diastereomers of the title compounds) in a ratio of 57:28:7:1:2:5

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

• several times, but the result was always the same (formation of 1a was observed in all experiments), though in some experiments a transesterification of the acetyl group to C(O)OEt group was observed in yields of 0–13% as confirmed by the 1H and 31P NMR spectra. We were unable to provide any direct

• explanation for the variation in the transesterification proportion. Etidronic acid was also tested as a starting material to prepare a derivative such as 1a [C(O)OEt group instead of Ac group], but the reaction did not occur under the same conditions as those used in the preparation of 1a. Our subsequent

• ) partial transesterification of bisphosphonate 1a before degradation of P-C-P bridge, 2) partial esterification of phosphonate group after the carbonate groups (R3) decomposition from compound 1a (this is proposed to occur rapidly after the addition of 40% NaOH) and before the degradation of P-C-P bridge

Large- scale ruthenium- and enzyme- catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol

• Krisztián Bogár,
• Belén Martín-Matute and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2007, 3, No. 50, doi:10.1186/1860-5397-3-50

• -phenylethanol (2) is addressed. The immobilized lipase Candida antarctica lipase B (CALB) was employed for the resolution, which shows high enantioselectivity in the transesterification. The ruthenium catalyst used, (η 5-C5Ph5)RuCl(CO)2 1, was shown to possess very high reactivity in the "in situ" redox

• , Candida antarctica lipase B, catalyzes the transesterification with excellent selectivity in the presence of the homogeneous ruthenium racemization catalyst 1. Isopropenyl acetate seems to be an appropriate acyl donor, which makes the purification of the product acetate very easy via simple distillation

Investigation of acetyl migrations in furanosides

• O. P. Chevallier and
• M. E. Migaud

Beilstein J. Org. Chem. 2006, 2, No. 14, doi:10.1186/1860-5397-2-14

• and Table 4). The proportion of intermolecular transesterification and de-esterification products increased when anhydrous KF conditions were used instead of commercial TBAF in THF (Table 3, condition C). Similarly, longer reaction time of the fluoride-catalysed desilylation reactions resulted in an

• acetyl moieties. Such direct transesterification is intermolecular and while it has been observed in nucleoside-phosphoramidite and glycoside chemistry,[20][21][22][23] this alkoxide-promoted intermolecular acetyl migration process has been overlooked in furanosides. The isolated quantities of 1c and 1d

• decreased by a factor of two upon dilution (1:10) when 1 was reacted with TBAF, while 1b formation remained rapid with no detection of 1a formation. Similarly, complete transesterification took place when riboside 6 was treated with acetyl riboside 1 under basic conditions (Scheme 6). Acetyl migration in