The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• coming close to a general route to introduce functionality into bisallenes at the present time seems to be the double SN2'-reaction of 2,4-hexadiyne-1,6-diol (63, e.g. R1 to R4 = aryl) and its derivatives with various nucleophiles (Scheme 13) [49][50]. Thus, heating the diols 63 with an aromatic or

• heteroaromatic thiol 64 provides the sulfur-substituted bisallene derivative 65 in good yields. Likewise, the stable diallenes 66 carrying phosphorus-containing substituents were obtained by heating the diols 63 with R52PCl [51][52][53][54]. How critically the substituents in the 3- and 4-position determine the

• at room temperature failed because they easily isomerized to the dienynes 69. The derivatives 71 can also be obtained from the isomeric diols 70 under comparable conditions, as shown by Braverman and co-workers. However, in only one case could these bisallene derivatives actually be isolated; all

Asymmetric desymmetrization of meso-diols by C₂-symmetric chiral 4-pyrrolidinopyridines

• Hartmut Schedel,
• Keizo Kan,
• Yoshihiro Ueda,
• Kenji Mishiro,
• Keisuke Yoshida,
• Takumi Furuta and
• Takeo Kawabata

Beilstein J. Org. Chem. 2012, 8, 1778–1787, doi:10.3762/bjoc.8.203

• pyrrolidinopyridine framework as a catalytic site. Some of these organocatalysts effectively promoted asymmetric desymmetrization of meso-diols via enantioselective acylation. Keywords: acylation; desymmetrization; hydrogen bond; meso-diol; nucleophilic catalyst; organocatalysis; Introduction Since the pioneering

• racemic diols (s: up to 12) [8] and amino alcohol derivatives (s: up to 54) [9]. Catalyst 2, readily prepared from L-proline, could be employed for the kinetic resolution of amino alcohol derivatives (s: up to 11) [10]. Chiral PPY catalysts with dual functional side chains at C(2) and C(4) of the

• pyrrolidine ring such as 3 were prepared from trans-4-hydroxy-L-proline. These catalysts were found to be moderately effective for the asymmetric desymmetrization of meso-diols [11]. C2-Symmetric PPY-catalyst 4 was found to be effective for the chemo- and regioselective acylation of carbohydrates [12][14][16

Synthesis of 5-oxyquinoline derivatives for reversal of multidrug resistance

• Torsten Dittrich,
• Nils Hanekop,
• Nacera Infed,
• Lutz Schmitt and
• Manfred Braun

Beilstein J. Org. Chem. 2012, 8, 1700–1704, doi:10.3762/bjoc.8.193

• purification in the coupling reaction with epoxide (R)-16. The spirocyclic compounds 6c–13c were obtained by standard acid-catalyzed reaction with the corresponding diols for the formation of acetals 6c–12c and propanedithiol for 13c, starting from N-acetyl-4-piperidone. Basic hydrolysis was found to be

On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• alkyne 5 with (S)-1,2 epoxynonane. Gold-catalyzed cycloisomerization (with desilylation) provided spiroketal diols 10a and 10b in a 32:68 ratio and in 89% total yield. Major spiroketal 10b could be converted to 10a in 15:1 dr by zinc-catalyzed isomerization. Both isomers (10a and 10b) were independently

• -spiroketals 21a and 21b was obtained in 71% overall yield from 20. The mixture of diols 21a and 21b converged to 21a (epimer 21b no longer observable by 1H NMR) upon treatment with zinc chloride. TEMPO oxidation of diol 21a led to the formation of cephalosporolide E (2, admixed with a minor diastereomer

Synthesis of functionalized macrocyclic derivatives of trioxabicyclo[3.3.0]nonadiene

• Sabine Leber,
• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2012, 8, 738–743, doi:10.3762/bjoc.8.83

• and Discussion Functional group manipulation on aromatic rings often starts with the nitro group. Therefore, a synthesis of suitable nitro-aromatic diols for combination with the diacid dichloride 3 was required. The desired 2-nitro-1,4-phenylene derivative 7 was prepared by treatment of hydroquinone

• with 3-bromopropanol followed by nitration of the resulting diol 6 (Scheme 2). The isomeric 1,2,3-trisubstituted aromatic 10 was obtained by etherification of nitroresorcinol (Scheme 3). The two diols 7 and 10 reacted readily with the diacid dichloride 3 in boiling toluene in the presence of

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• alkenes [15], alkynes [16][17], and benzyne [18][19], to give Δ2-isoxazolines and isoxazoles. These are interesting sources of bioactive compounds in their own right, but isoxazoles are particularly valuable for their latent functionality as β-hydroxyketones, β-aminoalcohols, 1,3-diols, and a range of

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

• Katharina C. Kress,
• Martin Kaller,
• Kirill V. Axenov,
• Stefan Tussetschläger and
• Sabine Laschat

Beilstein J. Org. Chem. 2012, 8, 371–378, doi:10.3762/bjoc.8.40

• . Starting from the corresponding diols 6a,b, 6-bromohexan-1-ol (7a) and 10-bromodecan-1-ol (7b) were obtained in moderate yields by bromination with aqueous HBr in toluene [35]. The bromides 7a,b were reacted with 4-cyano-1,1'-biphenol (8) in acetone in the presence of K2CO3 giving compounds 9a,b, bearing

Synthesis of 2-amino-3-arylpropan-1-ols and 1-(2,3-diaminopropyl)-1,2,3-triazoles and evaluation of their antimalarial activity

• Matthias D’hooghe,
• Stéphanie Vandekerckhove,
• Karen Mollet,
• Karel Vervisch,
• Stijn Dekeukeleire,
• Liesbeth Lehoucq,
• Carmen Lategan,
• Peter J. Smith,
• Kelly Chibale and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2011, 7, 1745–1752, doi:10.3762/bjoc.7.205

• variety of 2-amino-3-arylpropan-1-ols, anti-2-amino-3-aryl-3-methoxypropan-1-ols and anti-2-amino-1-arylpropan-1,3-diols were prepared selectively through elaboration of trans-4-aryl-3-chloro-β-lactams. In addition, a number of 2-(azidomethyl)aziridines was converted into novel 2-[(1,2,3-triazol-1-yl

• ). Furthermore, in order to provide access to the class of 2-aminopropan-1,3-diols, aziridines 7 were evaluated for the first time as substrates for a water-induced aziridine ring opening in an acidic medium. Thus, treatment of trans-2-aryl-3-(hydroxymethyl)aziridines 7 with one equiv of para-toluenesulfonic

• acid in a H2O/THF (1/1) solvent system [32] furnished novel anti-2-amino-1-arylpropan-1,3-diols 9a–d in good yields after 3 h at 40 °C, again in a regio- and stereospecific way (Scheme 1). The observed regio- and stereoselectivity in aminopropanols 8 and 9 can be rationalized by considering the ring

Planar-bilayer activities of linear oligoester bolaamphiphiles

• Jonathan K. W. Chui,
• Thomas M. Fyles and
• Horace Luong

Beilstein J. Org. Chem. 2011, 7, 1562–1569, doi:10.3762/bjoc.7.184

• -bromoalcohols prepared by mono-brominating the corresponding diols as described [16]. This gave the bis-bromides, which were subsequently displaced by the protected carboxylate anion of BOC-protected aniline 14 to give precursors 15, 16 and 17. Deprotection of the carbamate protecting groups under various

Coupled chemo(enzymatic) reactions in continuous flow

• Ruslan Yuryev,
• Simon Strompen and
• Andreas Liese

Beilstein J. Org. Chem. 2011, 7, 1449–1467, doi:10.3762/bjoc.7.169

• at 56% of overall conversion was achieved. In the continuous sequential synthesis of vic-diols in a multicatalyst system described by Liese [2], the incompatible reaction steps were successfully separated in a cascade of two enzyme membrane reactors as well. The first reactor contained benzoyl

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• prepared in situ from Me2AlCl and several chiral diols, were not catalytically active. However, the well-established Lewis acid [(R,R-TADDOLato)TiCl2] [82] (Scheme 1) displayed good catalytic activity (5 mol %, 1→1-F in 4 h) and gave (S)-1-F with an enantiomeric excess of 28% (for a complex incorporating

• 6), the reagents induced similar enantioselectivity. Ligand variations in the asymmetric titanium-catalyzed fluorination reaction We tested several chiral diols in the titanium-catalyzed asymmetric fluorination, but notable success was only achieved with TADDOL ligands [91]. We obtained several

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• processes. Furthermore, the catalyst lifetime can, in many cases, be dramatically improved under supercritical conditions, owing to reduced coking [69][70]. The selective monoprotection of 1,n-terminal diols is a characteristic example of how mono-substituted ethers can be selectively prepared versus the

• bis-substituted ones [71]. The use of an acid catalyst (Amberlyst 15) allows the formation of the corresponding mono-ethers by reaction of 1,6-hexanediol and other diols with simple alcohols under flow conditions (scCO2, 150 °C, 20 MPa, 1.15 mL·min−1). One of the most interesting results found was the

Carbamate-directed benzylic lithiation for the diastereo- and enantioselective synthesis of diaryl ether atropisomers

• Abigail Page and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1327–1333, doi:10.3762/bjoc.7.156

• ), two diols 8 and 9, available from previous work, were converted to the biscarbamates 10 and 11. The metallation of O-benzylcarbamates has been studied extensively by Hoppe [1][24][25][26], and the deprotonation of 10 was achieved with sec-BuLi in ether and the addition of acetone, returning 12 as a

Directed ortho,ortho'-dimetalation of hydrobenzoin: Rapid access to hydrobenzoin derivatives useful for asymmetric synthesis

• Inhee Cho,
• Labros Meimetis,
• Lee Belding,
• Michael J. Katz,
• Travis Dudding and
• Robert Britton

Beilstein J. Org. Chem. 2011, 7, 1315–1322, doi:10.3762/bjoc.7.154

• groups. The optimization and scope of this reaction are discussed, and the utility of this process is demonstrated in the one-pot preparation of a number of chiral diols as well as a short synthesis of the chiral ligand Vivol. Keywords: chiral diol; directed ortho-metalation; hydrobenzoin; Introduction

• The discovery of new chiral ligands and auxiliaries continues to expand the frontiers of catalytic asymmetric synthesis. In particular, C2-symmetric diols, such as (S)-BINOL (1) [1] and (−)-TADDOL (2) [2] (Figure 1), have garnered considerable attention owing to the wide variety of asymmetric

• . Importantly, a wide variety of chiral diols (e.g., Vivol (4)) are now readily accessible in optically pure form following this one-pot reaction. Although the range of electrophiles that engage in synthetically useful reactions with the tetralithio intermediate 8 is limited, the diiodohydrobenzoin 12 and bis

Lithium phosphonate umpolung catalysts: Do fluoro substituents increase the catalytic activity?

• Anca Gliga,
• Bernd Goldfuss and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2011, 7, 1189–1197, doi:10.3762/bjoc.7.138

• analyze the effect of fluoro substituents on the catalytic activity by using different fluorinated and nonfluorinated phosphonates as precatalysts in the benzoin coupling. Results and Discussion As precursors for six, seven and nine membered ring phosphonates, diols 1–4, and 6–8 were synthesized (Scheme 3

• nine ring phosphonates. The synthesis of these diols was realized by a double ortho lithiation of biphenyl and subsequent addition to the corresponding carbonyl compound. By this procedure, two asymmetric carbon centres and a chiral axis, which is fixed by intramolecular hydrogen bonds (6

• ) [31][32]. The energy differences of the terpene-based conformers are between 5.1 and 5.8 kcal/mol [32][33] (B3LYP/6-31++G**:AM1). The conversion of diols 1–5, 7, and 8 to the desired phosphonates can be achieved by twofold addition to phosphorus trichloride and subsequent hydrolysis. Diol 6 could not

Functionalization of anthracene: A selective route to brominated 1,4-anthraquinones

• Kiymet Berkil Akar,
• Osman Cakmak,
• Orhan Büyükgüngör and
• Ertan Sahin

Beilstein J. Org. Chem. 2011, 7, 1036–1045, doi:10.3762/bjoc.7.118

• towards the base for the hydroxy and the methoxy compounds. For example, the methoxy compounds aromatize to give 10 and 11, but the diols convert either to the epoxides by cyclization (Scheme 1 and Scheme 5) or to the alkene by elimination of 1 mol HBr (Scheme 6). In addition, however, the base-induced

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• from suitably substituted (Z)-2-en-4-yn-1-ols 5 [20]. A similar strategy has been applied to an efficient formation of substituted furans 9 through gold-catalyzed selective cyclization of enyne-1,6-diols 8 [21]. Nucleophilic attack of the hydroxy oxygen atom on 1-position to a gold-coordinated C–C

• available heteroatom-substituted propargyl alcohols 10 has been developed by Aponick and co-workers [22]. For the formation of tetrahydropyran analogs 13 and 15, the gold(I)-catalyzed cyclization of monoallylic diols 12 and 14 is an efficient method (Scheme 2) [23][24]. In addition to common organic

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

• Berenger Biannic,
• Thomas Ghebreghiorgis and
• Aaron Aponick

Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91

• able to make comparisons between how well different substrates function in the reaction. Previous papers detail the results with diols and include a variety of substrates with yields and reaction times [23][24][25]. While the isolated yield is the ultimate measure of how well the system has performed

• to vary the nature of the allylic leaving group and olefin geometry. These conditions are slightly different to those employed in the study of diols [23][24][25], differing in catalyst identity and loading (1 mol % (Ph3P)AuCl/AgOTf versus 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6). As mentioned above, the

• reaction shown in black, which proceeded to 96% conversion, while the reactions quenched at 1, 3, and 5 minutes went to 23%, 41%, and 52% conversion, respectively. Subsequently, a comparison between cis- and trans-diols 10 and 7 was made. As can be seen in Figure 3, both reactions were fairly rapid, with

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• in a rather selective manner, a similar route to deoxymannojirimycin (63) and 1-deoxyallonojirimycin (66) did not achieve the same degree of selectivity, presumably due to difficulties in transforming the endocyclic double bond of the RCM product 72 into the targeted trans diols. Clean epoxide

• modified Upjohn conditions, Scheme 22). For iminocyclitols containing trans diols at the 3- and 4-positions an epoxy functionality at the double bond in 125 was introduced. While the syn epoxide 128 led to a mixture of fagomine (129) and 3,4-di-epi-fagomine (130), the anti epoxide 127 gave 129 selectively

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues

• Lucie Brulikova and
• Jan Hlavac

Beilstein J. Org. Chem. 2011, 7, 678–698, doi:10.3762/bjoc.7.80

• styrene to afford nucleoside 147. The oxidation of alkene function in 147 with OsO4 led to a mixture of diastereomers of vicinal diols 148. For the introduction of the oligodeoxynucleotide 146, the dihydroxynucleoside 147 was converted to the corresponding phosphoramidite. This was carried out as follows

A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• 5,5-spiroketals, including cyclocondensation of ketone diols [6][7], the cycloisomerization of alkyne diols (Scheme 1) [8][9][10][11][12][13][14][15][16], oxidative spirocyclization of tetrahydrofuryl propanols [17][18][19][20], and others. Cyclocondensation of ketone diols is perhaps the most

• straighforward and the most used method, but the alternative procedures offer specific advantages. For example, the cycloisomerization of alkyne diols is more exothermic (Scheme 1) [21] and atom economical [22], and non-polar alkyne π-bonds are more compatible than ketones (kinetically stable) towards a number

• cyclocondensation of alkyne diols to give substituted furans (Scheme 3, Reaction 3) [35]. Our objective, laid out in Scheme 4, was to initiate cycloisomerization with a 5-endo-dig cyclization of the homopropargyl alcohol 6, followed by 5-exo-trig cyclization onto the resulting dihydrofuran, whilst avoiding

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• ], while the latter from p-toluenesulfonyl chloride in the presence of a base such as pyridine [13][17][18][19][20]. Dibromides I can also be obtained by the ring-opening of tetrahydropyrans VIII under the same conditions employed for the diols VII [2][12][21][22], or via phase-transfer catalysis

• are listed in Table 1. For completeness, thianes IV, diols VII, and tetrahydropyrans VIII are also included. Diols VII represent a convenient intermediate for the preparation of dibromides I or ditosylates II, and four routes to VII are presented in Scheme 1. The first route (Method 1A) involves six

• steps starting from alkylation of malonate diester followed by reduction of the esters, tosylation of the alcohols, carbon homologation with NaCN, hydrolysis of the cyano groups to carboxylic acids, and lastly a second reduction to VII. Overall yields of diols VII using Method 1A are around 10% [27][28

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• palladium-catalyzed reaction. To test the proposed mechanism of this reaction, first, bicyclonorcarene endoperoxides derived from cyano and carbomethoxy cycloheptatrienes were synthesized and converted into the corresponding diols. The reaction of diols with toluenesulfonyl isocyanate followed by a

• than the trans-coupling [23][24], we assigned the exo-configuration to the cyano group in 12. Selective reduction of the peroxide linkages in 12 and 13 with thiourea under very mild conditions afforded the diols 14 and 18a, respectively. For further characterization, the diols were converted to the

• diacetates 15 and 18b. The isomeric diols 14 and 18a were treated with 2 equiv of toluenesulfonyl isocyanate as described above to give the corresponding biscarbamates 16 and 19. Treatment of 16 and 19 with the palladium catalyst (as described above) resulted in the formation of oxazolidinone derivatives 17

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• is the formation of polyurethanes. Originally, there was considerable interest in producing water-borne polyurethane dispersions to replace the solvent-borne formulations and therefore much effort was expended in investigating the synthesis of polyurethane in aqueous miniemulsions. Hydrophobic diols

• miniemulsion. For example, castor oil (a triol) has been used as the monomer [102]. Li et al. showed that short diols can be also replaced efficiently by poly(tetramethylene glycol) [103]. The polyaddition reaction to form urethane bonds was also carried out with a cyclodextrin derivative and IPDI as the

• parameters were found to play a role in increasing the yield. The yield was higher if a) more hydrophobic monomers and b) diols with electron-donating groups were polymerized. The polycondensation of a diamine and sebacoyl chloride was carried out in direct miniemulsions in the presence of silica

β-Hydroxy carbocation intermediates in solvolyses of di- and tetra-hydronaphthalene substrates

• Jaya S. Kudavalli and
• Rory A. More O'Ferrall

Beilstein J. Org. Chem. 2010, 6, 1035–1042, doi:10.3762/bjoc.6.118

• ratio of cis to trans diols from cis and trans reactants together with a small amount of 2-tetralone. The product distribution for the trans isomer is shown in Scheme 3. The corresponding figures for the cis isomer are 76% cis and 20% trans dihydrodiols plus 4% 2-tetralone. The similarity of the product