The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• . Plausible explanation for chemoselective CM of diene 16 [25]. a) Efficient cross-metathesis of S-allylcysteine [17]. b) Comparison of relative reactivity between allylic heteroatom derivatives. a) Macrocycle synthesis by carbonyl-relayed RCM. b) Putative complex in carbonyl-relayed RCM [33]. a) Sulfur

Total synthesis of (±)-coerulescine and (±)-horsfiline

• Mukund G. Kulkarni,
• Attrimuni P. Dhondge,
• Sanjay W. Chavhan,
• Ajit S. Borhade,
• Yunnus B. Shaikh,
• Deekshaputra R. Birhade,
• Mayur P. Desai and
• Nagorao R. Dhatrak

Beilstein J. Org. Chem. 2010, 6, 876–879, doi:10.3762/bjoc.6.103

• 14. Finally, chemoselective reduction of amide 14 with n-BuLi and LAH (under the conditions reported in [27]) gave coerulescine. Compound 1, on treatment with N-bromosuccinimide, gave the 5-bromo derivative, which upon heating with sodium methoxide in the presence of cuprous iodide gave horsfiline in

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

• the keto moiety. Results of a detailed and systematic investigation of the reaction are described. Keywords: diols; esters; lactones; reduction; Introduction Chemoselective reductions of aldehydes, ketones and imines are generally accomplished using NaBH4 in methanol where other reducible functional

• 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

• ][22][23][24][25][26][27] for the chemoselective reduction of the keto group of all types of γ-oxoesters. Mechanistic rationale for diol formation during the reduction of a γ-aryl-α,β-unsaturated-γ-ketoester with methanolic NaBH4. Facile reduction of γ-aryl-γ-ketoesters to the corresponding diols with

Synthesis of lipophilic 1-deoxygalactonojirimycin derivatives as D-galactosidase inhibitors

• Georg Schitter,
• Elisabeth Scheucher,
• Andreas J. Steiner,
• Arnold E. Stütz,
• Martin Thonhofer,
• Chris A. Tarling,
• Stephen G. Withers,
• Jacqueline Wicki,
• Katrin Fantur,
• Eduard Paschke,
• Don J. Mahuran,
• Brigitte A. Rigat,
• Michael Tropak and
• Tanja M. Wrodnigg

Beilstein J. Org. Chem. 2010, 6, No. 21, doi:10.3762/bjoc.6.21

• desired free amine 15 [25], the key building block for further modifications (Scheme 2). The chemoselective acylation of the free amine 15 was conducted with three different benzoic acid derivatives in order to investigate the influence of the potential basicity of an additional nitrogen at the aromatic

• )-1-deoxygalactonojirimycin (15) from 12 via 14. Synthesis of lipophilic 1-deoxy-D-galactonojirimycin derivatives 16–18 by chemoselective acylation of 15. Synthesis of compounds 19 as well as 20 from primary amine 15. Synthesis of compound 22. Inhibitory activities of compounds 16–20 and 22 with β

Prediction of reduction potentials from calculated electron affinities for metal-salen compounds

• Sarah B. Bateni,
• Kellie R. England,
• Anthony T. Galatti,
• Handeep Kaur,
• Victor A. Mendiola,
• Alexander R. Mitchell,
• Michael H. Vu,
• Benjamin F. Gherman and
• James A. Miranda

Beilstein J. Org. Chem. 2009, 5, No. 82, doi:10.3762/bjoc.5.82

• advantage of this variant of the ERC reaction was the ability to effect the reaction at a more positive potential than the unmediated ERC reaction, resulting in a more chemoselective reaction [5]. The postulated mechanism of the reaction operated via a Ni(II)-salen radical anion as the active catalyst and

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• serve as universal precursors for the asymmetric synthesis of functionalised β2-amino acids containing acid-labile protected side chains. Diastereoselective alkylation of the tetrahydropyrimidinone is followed by a chemoselective two step degradation of the heterocycle to release the free β2-amino acid

• . Chemoselective reduction of 10 was carried out by reaction with sodium borohydride in the presence of Ni(OAc)2. The “nickel boride” formed as black precipitate serves as a highly active hydrogenation catalyst, whereas an excess of NaBH4 serves as hydrogen source [45][46]. The reaction reaches completion within

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

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

• insertion The laboratory of G.A. Sulikowski proposed a synthesis of 1,2-aziridinomitosenes [106][107] using as key transformations a Buchwald–Hartwig cross-coupling [108][109][110] and a chemoselective intramolecular carbon-hydrogen metal-carbenoid insertion reaction (Scheme 39). The chiral pyrolidine 136

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

• microwave irradiation. Keywords: chemoselective; lipase; microwave irradiation; zein number; Introduction Microwave assisted enzyme catalysis is a popular developing methodology in the field of green chemistry [1]. Enzymes have gained pivotal importance in the production of fine chemicals, pharmaceuticals

Chemoselective reduction of aldehydes by ruthenium trichloride and resin- bound formates

• Basudeb Basu,
• Bablee Mandal,
• Sajal Das,
• Pralay Das and
• Ashis K. Nanda

Beilstein J. Org. Chem. 2008, 4, No. 53, doi:10.3762/bjoc.4.53

• Basudeb Basu Bablee Mandal Sajal Das Pralay Das Ashis K. Nanda Department of Chemistry, University of North Bengal, Darjeeling 734 013, India 10.3762/bjoc.4.53 Abstract A simple, chemoselective transfer hydrogenation of aryl aldehydes with the aid of Amberlite® resin formate (ARF), a stable H

• the ability of Ru(III) salts in the CTH of aryl ketones using the poly-ionic resin formate. Our studies reported herein constitute an efficient method for chemoselective transfer hydrogenation of aryl aldehydes with the aid of resin-supported formate in the presence of catalytic (2.5 mol%) amount of

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• 82 yielded the butenolide 167. Hydrogenation of the double bond afforded (+)-squamocin K, while diastereoselective dihydroxylation of the same double bond yielded (5S)-hydroxyparviflorin 168. Chemoselective deoxygenation of the C-5 hydroxyl group afforded parviflorin, spectroscopically identical to

Total synthesis of the indolizidine alkaloid tashiromine

• Stephen P. Marsden and
• Alison D. McElhinney

Beilstein J. Org. Chem. 2008, 4, No. 8, doi:10.1186/1860-5397-4-8

• allylsilanes. Specifically, cross-metathesis of N-pentenylsuccinimide 5 with allyltrimethylsilane (6) [39] followed by chemoselective partial reduction of the imide would give the cyclisation precursor 3 in short order. Further, the use of chiral allylsilanes as cross-metathesis partners would potentially

• appropriate chiral allylsilane followed by chemoselective partial reduction by borohydride. Thereafter, exposure to acid would generate an N-acyliminium ion, which would cyclise through a chair-like transition state with the nascent alkenyl side-chain equatorially disposed, as in the racemic series (Figure 1

Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• -benzyl-1-phenylethylamine, was converted into the primary amine (−)-15 and thence in several steps into the thiolactam (+)-16. Eschenmoser sulfide contraction [22][23] with ethyl bromoacetate yielded the key enaminone intermediate (+)-17, chemoselective reduction of the saturated ester of which produced

• the alcohol (−)-18. The bicyclic core of the alkaloid was then constructed by a cycloalkylation that took advantage of the nucleophilic reactivity of the enaminone, following which a chemoselective and reasonably diastereoselective (88:12) reduction of the alkene bond of the bicyclic enaminone (+)-19

Tether- directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

• Peter J. Jervis and
• Liam R. Cox

Beilstein J. Org. Chem. 2007, 3, No. 6, doi:10.1186/1860-5397-3-6

• proximity of the reacting partners, combined with a reduction in the degrees of freedom in the system, render the intramolecular reaction more entropically and kinetically favourable. This can result in a more stereo-, regio- and chemoselective process, which is often reflected in an increased yield of the

Hydrogenation of aromatic ketones, aldehydes, and epoxides with hydrogen and Pd(0)EnCat™ 30NP

• Steven V. Ley,
• Angus J. P. Stewart-Liddon,
• David Pears,
• Remedios H. Perni and
• Kevin Treacher

Beilstein J. Org. Chem. 2006, 2, No. 15, doi:10.1186/1860-5397-2-15

• University described the selective reduction of electron deficient and neutral aryl ketones to benzylic alcohols using Pd(0)EnCat™ 30NP as catalyst and a mixture of HCOOH/Et3N as the source of hydrogen [16]. Under these conditions they also achieved the chemoselective hydrogenolysis of aryl epoxides [17

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

• ribosides, acyl migration could be prevented when desilylation was catalysed by cerium ammonium nitrate. Introduction Over the years, a number of methods aimed at achieving chemoselective acylation of carbohydrates have been developed.[1][2][3] In addition to the challenges encountered in the selective

• experimental data). Riboside 1 was synthesised from ribose in 47% overall yield via a chemoselective silylation of the C-5 primary hydroxyl group of 2,3-O-isopropylidene ribose (Scheme 2). The acetylated xyloside 2 and riboside 3 were both synthesised from xylose in 46% and 45% overall yield, respectively. The

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

• and chemoselective thioacylating agent using the reaction of acyl chlorides with dithiophosphoric acid in the presence of pyridine or triethylamine. [51][52][53] In another study we decided to investigate the reaction of the ambident nucleophile ammonium O,O'-diethyl thiophosphate salt with acyl