Approaches to α-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

• Sosale Chandrasekhar and
• V. Mohana Rao

Beilstein J. Org. Chem. 2012, 8, 1393–1399, doi:10.3762/bjoc.8.161

• preparation of 1 is also presented herein). Ketone 1 was α-alkylated in high yields to various 2 via sodium hydride deprotonation and reaction of the resulting enolate with a variety of alkyl bromides or iodides. Alkyl derivatives 2 may be converted conventionally to the corresponding oximes 3. The Beckmann

Studies on the substrate specificity of a GDP-mannose pyrophosphorylase from Salmonella enterica

• Lu Zou,
• Ruixiang Blake Zheng and
• Todd L. Lowary

Beilstein J. Org. Chem. 2012, 8, 1219–1226, doi:10.3762/bjoc.8.136

• methoxide and then tert-butyldiphenylchlorosilane in DMF. Benzylation of 32 using benzyl bromide and sodium hydride gave 33 in 84% yield. The TBDPS group was then cleaved and replaced with a methyl group to give the 6-methoxy compound 35 in 72% yield over two steps. The protected dibenzyl phosphate 36 was

Synthesis of 4” manipulated Lewis X trisaccharide analogues

• Christopher J. Moore and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2012, 8, 1134–1143, doi:10.3762/bjoc.8.126

• conditions the α-tripivaloate 15, selectively acylated at O-2, O-3 and O-6, was obtained pure and free of β-anomer (64%). The free hydroxy group in alcohol 15 was then deprotonated with sodium hydride and allowed to react with methyl iodide, yielding the 4-OMe galactoside 16 in very good yield. In turn

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• the molecules via hydrogen bonds. The idea was to synthesize europium(III) complexes containing the new ligands. Since the pyrrole amine is a very weak acid (pKa = 23.0) [17] it can only be deprotonated by hard bases, such as n-butyllithium or sodium hydride [18]. Therefore we chose to work in water

Hybrid super electron donors – preparation and reactivity

• Jean Garnier,
• Douglas W. Thomson,
• Shengze Zhou,
• Phillip I. Jolly,
• Leonard E. A. Berlouis and
• John A. Murphy

Beilstein J. Org. Chem. 2012, 8, 994–1002, doi:10.3762/bjoc.8.112

• sodium hydride base has a very important and selective effect on some of these electron-transfer reactions, and a rationale for this is proposed. Keywords: aryl iodide; electron transfer; hybrid donors; reduction; Introduction Alkenes that are substituted by four heteroatoms are notable for their ease

• ], and so its capability as an electron donor was tested. To test reactivity, donor 11 was prepared in situ and treated with the substrates 28 and 30 at room temperature (Scheme 2). Simple substrate 28 [35] was added to 11, prepared by adding disalt 19 (1.5 equiv) to excess sodium hydride (15 equiv). As

• different conditions than with 28. Donor 11 was prepared by using disalt 19 (3 equiv) added to the excess sodium hydride (15 equiv), and the resulting donor solution was filtered to remove excess NaH before substrate 30 was added. (Previous experience had raised suspicion that the excess NaH could

Low-generation dendrimers with a calixarene core and based on a chiral C₂-symmetric pyrrolidine as iminosugar mimics

• Marco Marradi,
• Stefano Cicchi,
• Francesco Sansone,
• Alessandro Casnati and
• Andrea Goti

Beilstein J. Org. Chem. 2012, 8, 951–957, doi:10.3762/bjoc.8.107

• , alkylation of the hydroxy groups of 7 with the 2-ethoxycarbonylmethyl linker was problematic. In fact, when sodium hydride was used as a deprotonating agent, no reaction occurred after in situ addition of ethyl bromoacetate. However, a mixture of mono-(8') and di-(8) substituted products was obtained by

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• diphosphonates [20][21] for tetravalent anchoring on the ITO surface. The geminal diphosphonates 7 were synthesized from methylene bis(phosphonic dichloride) 8 (Scheme 1) [20][21]. Conversion with benzyl alcohol and pyridine as a base yielded tetrabenzyl methylene bisphosphonate 9. Activation with sodium hydride

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

• corresponding glucuronyl 1-thiol 3 in 89% yield [17][18]. Reaction of 3 with an excess of 1,2-dibromoethane (3–4 equiv) in DMF in the presence of sodium hydride, with the strict exclusion of oxygen, afforded the 2-bromoethyl 1-thioglycoside 4 in 80% yield. Under these conditions formation of the bis

Volatile organic compounds produced by the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria 85-10

• Teresa Weise,
• Marco Kai,
• Anja Gummesson,
• Armin Troeger,
• Stephan von Reuß,
• Silvia Piepenborn,
• Francine Kosterka,
• Martin Sklorz,
• Ralf Zimmermann,
• Wittko Francke and
• Birgit Piechulla

Beilstein J. Org. Chem. 2012, 8, 579–596, doi:10.3762/bjoc.8.65

• stirred, ice-cooled solution of 2.0 g (23.8 mmol) rac-4-pentyne-2-ol in 50 mL dry THF was slowly added 1.20 g (49.9 mmol) sodium hydride. The reaction mixture was warmed to room temperature, and stirring was continued until the formation of hydrogen ceased. Subsequently, a solution of 4.27 g (25.0 mmol

Acceptor-influenced and donor-tuned base-promoted glycosylation

• Stephan Boettcher,
• Martin Matwiejuk and
• Joachim Thiem

Beilstein J. Org. Chem. 2012, 8, 413–420, doi:10.3762/bjoc.8.46

• , elimination became the dominant reaction and led to the corresponding glycals. Hence, and based on the workup, the recovery of glycosyl halides was neither practicable nor achieved. Experimental General: All reagents were purchased from commercial sources and used as received. Sodium hydride (NaH) was used as

• and 35 were published previously [1]. General Procedure: Base-promoted glycosylations: The acceptor molecule (1.0 mmol) was dissolved in dry dimethylformamide (2–4 mL), and sodium hydride (1.1–1.3 mmol for each hydroxy group; as a 60% suspension in paraffin) was added. After being stirred for one hour

Fluorescent hexaaryl- and hexa-heteroaryl[3]radialenes: Synthesis, structures, and properties

• Antonio Avellaneda,
• Courtney A. Hollis,
• Xin He and
• Christopher J. Sumby

Beilstein J. Org. Chem. 2012, 8, 71–80, doi:10.3762/bjoc.8.7

• 11 using thionyl chloride [35][36]. Initial attempts to synthesise 3 using the standard procedure [15][16] were unsuccessful. In fact, the far greater acidity of 11 (compared to 6 or 4,4’-dicyanodiphenylmethane) allowed the use of sodium hydride instead of n-butyllithium as a base in the synthesis of

• , 76.10; H, 3.01; N, 20.89%; found C, 75.82; H, 3.01; N, 21.10. Hexakis(3,4-dicyanophenyl)[3]radialene (3). 60% Sodium hydride (50 mg, 1.26 mmol) was placed in a dry two-necked flask under argon. Degassed DMF (3 mL) was added and the suspension was stirred for 15 min. Then the mixture was cooled to 0 °C

Synthesis of enantiomerically enriched (R)-¹³C-labelled 2-aminoisobutyric acid (Aib) by conformational memory in the alkylation of a derivative of L-alanine

• Stephen P. Fletcher,
• Jordi Solà,
• Dean Holt,
• Robert A. Brown and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1304–1309, doi:10.3762/bjoc.7.152

• oligomers. We now report in detail a practical method for the enantioselective synthesis and enantiomeric assignment of a derivative of (R)-1*. Results and Discussion L-Alanine hydrochloride 2 was converted to its sodium salt either in situ with two equiv sodium hydride, or (preferably, and more

• , protected Aib (R)-6* for use in the synthesis, on gram scale, of spectroscopic probes for helicity [56]. Experimental (S)-2,2-Dimethyl-4-methyl-3-(1-naphthoyl)-oxazolidin-5-one (3): By a modification of the method of Branca [36][57], sodium hydride (575 mg of a 60% dispersion in mineral oil, 12.4 mmol) was

Carbasugar analogues of galactofuranosides: α-O-linked derivatives

• Jens Frigell and
• Ian Cumpstey

Beilstein J. Org. Chem. 2010, 6, 1127–1131, doi:10.3762/bjoc.6.129

• configuration) followed by intramolecular displacement of the C2 tosylate (with inversion of configuration). We synthesised the same epoxide 4 (78%) by treatment of isolated 3,5,6-tri-O-benzyl-2-O-(toluene-4-sulfonyl)-4a-carba-β-D-galactofuranose [9] with sodium hydride in DMF. We investigated ring-opening of

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

• 1-chloro-1,2,3,4-tetrahydronaphthalene [25] were also prepared by literature methods. cis-1-Hydroxy-2-methoxy-1,2-dihydronaphthalene (6-cis). To a solution of cis-1,2-dihydroxy-1,2-dihydronaphthalene (0.5 g, 3.1 mmol) in DMF (20 mL), was added sodium hydride as a 60% dispersion on mineral oil (0.15

Synthesis of 5-(6-hydroxy-7H-purine-8-ylthio)- 2-(N-hydroxyformamido)pentanoic acid

• Yanmei Zhang,
• Greg Elliot,
• Adrian Saldanha,
• Igor Tsigelny,
• Dennis Carson and
• Wolf Wrasidlo

Beilstein J. Org. Chem. 2010, 6, 742–747, doi:10.3762/bjoc.6.93

• 8 with triphenylphosphine in carbon tetrabromide resulted in the bromide 9 [5][6], which was coupled to mercaptopurine 9’ in the presence of sodium hydride in DMF to yield 10 [7][8] in excellent yield. Removal of the N-Troc group with zinc in acetic acid gave intermediate 11 and subsequent N

• ’ (50.0 mg, 1 equiv) in DMF (1.0 mL) at 0 °C, was added sodium hydride (11.9 mg, 1.1 equiv). After stirring at 0 °C for 2 h, a solution of compound 9 (169.0 mg, 1 equiv) in DMF (0.3 mL) was added within 1 min. The resulting mixture was stirred for 25 min, then quenched with ammonium chloride The mixture

Synthesis of the fluorescent amino acid rac-(7-hydroxycoumarin-4-yl)ethylglycine

• Manfred Braun and
• Torsten Dittrich

Beilstein J. Org. Chem. 2010, 6, No. 69, doi:10.3762/bjoc.6.69

• selective protection of the phenolic hydroxyl group, the tert-butyl(dimethyl)silyl group [14] was chosen. Thus, coumarin 3 was treated with one equivalent of sodium hydride to generate the phenolate by selective deprotonation without abstraction of the proton from the primary alcohol moiety. Subsequent

• line was charged with alcohol 3 (385 mg, 1.87 mmol) and closed with a septum. The air in the flask was replaced by nitrogen, and dry THF (10 mL) was injected by syringe. The septum was removed for a short time, and a 60% suspension of sodium hydride in mineral oil (74.8 mg, 1.87 mmol) added in one

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• was carried out in the presence of sodium hydride in DMF at different temperatures and occurred preferentially at the ortho- and para-positions of the aromatic ring (Scheme 31). Other substituted phenols were used as substrates under conditions yielding only C-trifluoromethylated products [36

Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs

• Dhananjaya Sahoo,
• Susanne Thiele,
• Miriam Schulte,
• Navid Ramezanian and
• Adelheid Godt

Beilstein J. Org. Chem. 2010, 6, No. 57, doi:10.3762/bjoc.6.57

• because the removal of HOP requires refluxing in toluene for several hours in the presence of sodium hydride or potassium hydroxide [34][36][37][38][42][50][51][52][76] whereas we expected that HOE could be detached through treatment with γ-MnO2 and powdered KOH in diethyl ether at room temperature, i.e

9,10-Dioxa-1,2-diaza-anthracene derivatives from tetrafluoropyridazine

• Graham Pattison,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• John A. Christopher and
• David D. Miller

Beilstein J. Org. Chem. 2010, 6, No. 45, doi:10.3762/bjoc.6.45

• ) was dissolved in THF (20 mL) and added to sodium hydride (0.07 g, 1.8 mmol, 60% dispersion in mineral oil) which was cooled to 0 °C and stirred. Tetrafluoropyridazine (3) (0.25 g, 1.64 mmol) was added slowly and the mixture stirred at 0 °C for 8 h. The solvent was evaporated and the crude material

• ), sodium hydride (0.138 g, 3.45 mmol, 60% dispersion in mineral oil), tetrafluoropyridazine (0.25 g, 1.64 mmol) and THF (20 mL) gave 3,6-difluoro-4,5-diphenoxypyridazine (8) (0.29 g, 59%) as a white solid; mp 123–124 °C; Anal. Calcd for C16H10F2N2O2: C, 64.0; H, 3.4; N, 9.3%. Found: C, 63.7; H, 3.5; N, 9.2

• , C-3); 19F NMR (658 MHz, CDCl3 δF): −88.2 (s); MS (ES+) m/z: 301 ([MH]+, 100%). Synthesis of 3,4-difluoro-9,10-dioxa-1,2-diaza-anthracene (5) Catechol (0.80 g, 7.2 mmol) was dissolved in THF (20 mL) at 0 °C under an argon atmosphere with stirring and added to sodium hydride (0.35 g, 14.5 mmol, 60

A short and efficient synthesis of valsartan via a Negishi reaction

• Samir Ghosh,
• A. Sanjeev Kumar and
• G. N. Mehta

Beilstein J. Org. Chem. 2010, 6, No. 27, doi:10.3762/bjoc.6.27

• -valine methyl ester hydrochloride (2) in the presence of triethylamine in dichloromethane at 0 °C to afford methyl N-pentanoyl-L-valinate in 95% yield. Compound 3 was N-protected with 1-bromo-4-(bromomethyl)benzene in presence of sodium hydride in tetrahydrofuran to give methyl N-(4-bromobenzyl)-N

• ). Sodium hydride dispersion (60%) in mineral oil (1.83 g, 46.51 mmol) was added to a solution of compound 3 (5.0 g, 23.25 mmol) and 1-bromo-4-(bromomethyl)benzene (4) (6.39 g, 25.58 mmol) in tetrahydrofuran (80 mL). The reaction mixture was refluxed for 1 h. After cooling, the mixture was diluted with

Convergent syntheses of Le^X analogues

• An Wang,
• Jenifer Hendel and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2010, 6, No. 17, doi:10.3762/bjoc.6.17

• trisaccharide 3, the 6-benzylthiohexyl glycoside 32 was also prepared from the 6-chlorohexyl glycoside 29. Thus, the chloride 29 was allowed to react for 16 h with excess benzylthiol (15 equiv) and sodium hydride (15 equiv) in DMF at 80 °C. These reaction conditions led to the displacement of the chloride as

Self-association of an indole based guanidinium-carboxylate-zwitterion: formation of stable dimers in solution and the solid state

• Carolin Rether,
• Wilhelm Sicking,
• Roland Boese and
• Carsten Schmuck

Beilstein J. Org. Chem. 2010, 6, No. 3, doi:10.3762/bjoc.6.3

• -indole-2-carboxylate 3 was reduced by reaction with hydrogen in the presence of Pd/C to provide the amine 4 in a yield of 98%. For the next stept, first, thiourea was N-Boc-protected at both amino-functions following a literature procedure [20]. Thiourea was deprotonated with sodium hydride and

• (w), 2939 (w), 1668 (s), 1250 (s), 1215(s) cm−1; HR-MS (ESI) calcd for [M+H]+: 205.0972; found 205.0979. N,N’-Di-(tert-butoxycarbonyl)thiourea (5): To a stirred solution of thiourea (570 mg, 7.50 mmol) in dry tetrahydrofuran (150 mL) sodium hydride (1.35 g, 33.80 mmol, 60% in mineral oil) was added

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• selectively mesylated on hydroxyl 2. Treatment with sodium hydride formed the epoxide. The acetate was removed and the epoxide was opened with lithium azide at 150°C. The two resulting alcohols were mesylated and the primary mesylate displaced with benzylamine. The resulting secondary amine was benzylated to

A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed- bed microreactor

• Andrew Bogdan and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2009, 5, No. 17, doi:10.3762/bjoc.5.17

• catalysts functionalized with an acetylene moiety can be tethered to AO using a Huisgen cycloaddition [39]. Azide-functionalized AO resin (AO-N3, 2) was prepared by treating AO with sodium azide (Scheme 1) [41]. The coupling of 4-hydroxy-TEMPO 3 with propargyl bromide (4) using sodium hydride yielded the

• (2 × 50 mL), Et2O (1 × 25 mL), and dried under vacuum. Elemental analysis afforded a loading of 1.0 mmol N3/g resin. Propargyl ether TEMPO 5 Sodium hydride (150 mg, 6.3 mmol, 1.1 equiv) was added to DMF (10 mL) and stirred at RT. 4-hydroxy-TEMPO (1.02 g, 5.9 mmol, 1.0 equiv) in DMF (10 mL) was added

• drop wise to the sodium hydride suspension at 0 °C and stirred until gas evolution ceased. Propargyl bromide (80% in toluene, 800 μL, 7.4 mmol, 1.3 equiv) in DMF (10 mL) was added at 0 °C and the reaction was allowed to warm up to RT and stirred overnight. The reaction was quenched with water and the

End game strategies towards the total synthesis of vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A

• Brett D. Schwartz,
• Craig M. Williams and
• Paul V. Bernhardt

Beilstein J. Org. Chem. 2008, 4, No. 34, doi:10.3762/bjoc.4.34

• epoxide ring opened product (i.e. 28) was isolated (via epoxide 29). Subsequent treatment of the crude material (i.e. 28) with sodium hydride gave as the sole product the TBS protected α-hydroxy ketone 30 in 80% yield over two steps, via a 1,2-Brook rearrangement. The unprotected derivative 31 could be