Total synthesis of panicein A₂

• Lili Yeung,
• Lisa I. Pilkington,
• Melissa M. Cadelis,
• Brent R. Copp and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 1991–1996, doi:10.3762/bjoc.11.215

• . to provide ketone 12 in 66% yield [8]. The selective reduction of the olefin in α,β-unsaturated ketone 12 was then attempted using the Raney nickel catalyst under hydrogen as previously reported [8]; unfortunately no product 13 was formed. Following this, a range of conditions were employed to reduce

Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha,
• Ongolu Ravikumar and
• Jadab Majhi

Beilstein J. Org. Chem. 2015, 11, 1503–1508, doi:10.3762/bjoc.11.163

• ]. Results and Discussion To begin with, the oxidation of dicyclopentadiene (5) in the presence of SeO2 gave 1α-dicyclopentadienol (6), which on treatment with pyridinium chlorochromate (PCC) [31] delivered the known tricyclic enone 4. Selective reduction of enone 4 with Zn in AcOH/EtOH under reflux

Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides

• Zsolt Szakonyi,
• Reijo Sillanpää and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2014, 10, 2738–2742, doi:10.3762/bjoc.10.289

• obtained. These include the selective reduction of β-enamino ester enantiomers [14], enzyme-catalyzed kinetic resolution [15], and a variety of asymmetric syntheses, for example, the enantioselective syntheses of β-lactams followed by ring opening [16][17], or the enantioselective desymmetrization of

• steps. The selective reduction of the isopropenyl double bond over a Pt/C catalyst resulted in 8A–D. The subsequent removal of the benzyl groups by hydrogenolysis over palladium on carbon (Pd/C) in a 1:1 mixture of n-hexane/EtOAc for 24 h gave primary amino esters 9A–D in excellent yields. The final

An integrated photocatalytic/enzymatic system for the reduction of CO₂ to methanol in bioglycerol–water

• Michele Aresta,
• Angela Dibenedetto,
• Tomasz Baran,
• Antonella Angelini,
• Przemysław Łabuz and
• Wojciech Macyk

Beilstein J. Org. Chem. 2014, 10, 2556–2565, doi:10.3762/bjoc.10.267

• ][11][18][19] and its use as a H-source providing its oxidized derivatives (or even C2 molecules [11]) may be an interesting path for the economically viable use of large volumes of CO2. Our ultimate goal is to attain a highly efficient and selective reduction of NAD+ to 1,4-NADH or other equally

• results in the conversion into a hydrido form. This product is an efficient and selective reduction catalysts of NAD+ to 1,4-NADH [22]. The resulting active hydrido form, [Cp*Rh(bpy)H]+ 3, transfers a hydride ion to the 4-position of NAD+ (coordination to the amide-carbonyl-O-atom) thereby exclusively

• to drive the in situ selective reduction of NAD+ cofactor to 1,4-NADH. This process works particularly well in the presence of a [Cp*Rh(bpy)H2O]Cl2 complex playing the role of the electron transfer mediator. Our studies demonstrate that the photocatalyst is able to utilize visible light for

Synthesis of aromatic glycoconjugates. Building blocks for the construction of combinatorial glycopeptide libraries

• Markus Nörrlinger and
• Thomas Ziegler

Beilstein J. Org. Chem. 2014, 10, 2453–2460, doi:10.3762/bjoc.10.256

• LiOH solution in THF afforded the corresponding carboxylic acid 4 in 96% yield. Next, acid 4 was converted into tert-butyl ester 5 in 89% overall yield by a two-step procedure via the corresponding intermediate acid chloride (Scheme 1). Selective reduction of the azido group in 5 without affecting the

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• achieved by ozonolysis to give an aldehyde, selective reduction of the latter with 9-BBN, and protection of the obtained primary alcohol as its TBS ether. N-Deprotection to give 120 was followed by acylation with benzyloxalyl chloride and treatment with triethylphosphite at elevated temperature to yield

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• protection of the amine was followed by selective reduction of the methyl ester [125]. Protection of the resulting alcohol gave tetracycle 140. The remaining ester 140 (see Scheme 18) was then converted to the corresponding acid, followed by anhydride formation. Introduction of an acyl azide resulted in a

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• alcohols of the structure A (Scheme 6). This alcohol can be selectively reduced either to cis- (B) or trans-allylic alcohol C. cis-Selective reduction of A can be achieved with Lindlar’s catalyst with H2 under atmospheric pressure. The thermodynamic trans-allylic alcohol C arises from the reaction of A

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• the desired precursor 14 in pure form in 71% yield. To avoid the formation of the inseparable byproduct, we investigated a reversed order of steps. To this end, 12 was first desilylated to allyl alcohol 15, which was then converted to butenoate 16, again via Steglich esterification. For the selective

• reduction of the enoate 16, the Stryker–Lipshutz protocol was again the method of choice and optimized conditions eventually furnished 14 in 87% yield (Scheme 3). For the Stryker–Lipshutz reduction of 16 slightly different conditions were used than for the reduction of 12. In particular, tert-butanol was

A practical synthesis of long-chain iso-fatty acids (iso-C₁₂–C₁₉) and related natural products

• Mark B. Richardson and
• Spencer J. Williams

Beilstein J. Org. Chem. 2013, 9, 1807–1812, doi:10.3762/bjoc.9.210

• methylmagnesium bromide to the ester/lactones and selective reduction of the resulting tertiary alcohols. Thus, the C12, C17 and C18 iso-fatty acids were obtained in three steps from commercially-available starting materials, and the remaining C13–C16 and C19 iso-fatty acids were prepared by homologation or

• approach to the iso-C12–C14 fatty acids 1–3 commenced from methyl undec-10-enoate (methyl undecylenate) 9. Reaction of 9 with methylmagnesium bromide afforded the tertiary alcohol 10 in 98% yield (Scheme 1). Selective reduction of the tertiary alcohol of 10 was achieved by ‘ionic hydrogenation’ with

• lactone pentadecanolide (exaltolide, 15) [57], a natural product that is produced industrially for use as a musk-odored perfumery fixative. Reaction of 15 with methylmagnesium bromide afforded the tertiary alcohol 16 in 98% yield (Scheme 2). Selective reduction of the tertiary alcohol of 16 was achieved

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

• from one of the Lewis basic sulfur atoms, derivatization to a lactone was carried out. The dithiane was cleaved to the ketone 18, which underwent a 1,3-syn-selective reduction [45]. The resultant diol 19 was subjected to acidic conditions to effect cleavage of the tert-butyl ester and lactonization to

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• includes the selective reduction of nitro groups to amines in the presence of ketones (Scheme 11) [50][51], and the oxidation of benzaldehyde to benzoic acid, albeit with incredibly poor conversion [52]. The conversion of L-lysine (32) to L-pipecolinic acid (33, Scheme 12) has also been investigated by

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• conditions were tested, but no system for selective reduction of the nitro group was found. Diazotization was carried out with the aim to prepare 1,2-diarylethane 9d from aniline 8d (Scheme 3). A combination of sodium nitrite and phosphoric acid was used. (With HCl, substitution of the amino function by a

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• enynes was achieved by selective reduction of the triple bond by making use of Raney nickel (Table 3). We found that the electron-rich enol ether moiety remains untouched, when reaction times of less than four hours were chosen in the case of the enynes 9e–9h. It should be noted that methanol was a

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• believed that a controlled, chemoselective reduction would offer more options in any synthesis, and thus several commercially available reducing agents were screened in order to achieve selective reduction of only one lactam carbonyl. A notable find was that, by short exposure of denitrated heterocycle 10a

Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium

• Michael Dobmeier,
• Josef M. Herrmann,
• Dieter Lenoir and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 330–336, doi:10.3762/bjoc.8.36

• -group tolerance during this reduction step is essential since various other groups are usually present. A number of synthetic procedures have been developed, which allow selective reduction, but only a few one-step transformations are known, which use either titanium(III) [5][6][7][8] or different metal

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

• of 6 [18]. Selective reduction of the peroxide linkage in 6 was carried out with thiourea under very mild conditions to give the diol 7 [19]. Since only the oxygen–oxygen bond is broken in this reaction, the configuration at all carbon atoms is preserved. Oxazolidinone 9 was synthesized by two

• 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

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

• -24146223 10.3762/bjoc.6.94 Abstract 4-Aryl-4-oxoesters undergo facile reduction of both the keto and the ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnish the corresponding 1,4-butanolides via selective reduction of

• combination with various additives [14][15] including at a cationic micellar surface [16], selective reduction of the keto group in oxoesters has been accomplished using potassium borohydride in refluxing ethanol [17] where the product distribution critically depends on the relative proportions of substrate

• ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnished the corresponding 1,4-butanolides via selective reduction of the keto moiety. These results, to the best of our knowledge, have no literature precedence. We

Synthesis of a novel analogue of DPP-4 inhibitor Alogliptin: Introduction of a spirocyclic moiety on the piperidine ring

• Arumugam Kodimuthali,
• Padala Lakshmi Prasunamba and
• Manojit Pal

Beilstein J. Org. Chem. 2010, 6, No. 71, doi:10.3762/bjoc.6.71

• functionalized cyclopropyl ring (step i, Scheme 1) via a conventional C–C bond forming reaction. The reaction proceeded well to afford the functionalized cyclopropane derivative 1 as a result of the formation of two C–C bonds in a single step. Selective reduction of the cyano group of the resulting cyanoester 1

Synthesis of gem-difluoromethylenated analogues of boronolide

• Jing Lin,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2010, 6, No. 37, doi:10.3762/bjoc.6.37

• the key γ,γ-gem-difluoromethylenated α,β-unsaturated-δ-lactone scaffold could be constructed via an oxidation–cyclization reaction of intermediate A according to our published procedures [22]. cis-Selective reduction of homopropargyl alcohol B would provide the homoallylic alcohol A. The alcohol B

Acid- mediated reactions under microfluidic conditions: A new strategy for practical synthesis of biofunctional natural products

• Katsunori Tanaka and
• Koichi Fukase

Beilstein J. Org. Chem. 2009, 5, No. 40, doi:10.3762/bjoc.5.40

• selective reduction of galactose derivative 10 gave the 6-O-benzyl derivative 16 in 91% yield (entry 6). It is worthwhile mentioning that the established microfluidic reaction reproducibly provided the O-benzylated compounds 11–16 in greater than 90% yields in all cases, out of the three experiments

The first direct synthesis of β-unsubstituted meso- decamethylcalix[5]pyrrole

• Luis Chacón-García,
• Lizbeth Chávez,
• Denisse R. Cacho and
• Josue Altamirano-Hernández

Beilstein J. Org. Chem. 2009, 5, No. 2, doi:10.3762/bjoc.5.2

• ) from the sterically hindered diaryldi(pyrrol-2-yl)methane with 25% yield; and b) through the conversion of a calix[6]furan into the corresponding calix[6]pyrrole by an opening process of the six heterocycles, a selective reduction of the double bond and then a Paal-Knorr condensation with ammonium

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

• by conversion to the epoxide 80. Addition of the C3-C13 fragment in a copper-catalyzed Grignard reaction afforded 81. The butenolide ring in 4,5-dehydro-cis-solamin (83) was put in place using a ruthenium catalyzed Alder-ene reaction of 81 with 82. Final selective reduction of the 4,5-double bond

• ) 319 to afford 321. Introduction of the unprotected butenolide (as 323) by epoxide opening with lithiated 322 followed by selective reduction and deprotection afforded bullatacin. Total synthesis of rollidecins C and D Rollidecin C (324) and rollidecin

Synthesis of (–)-Indolizidine 167B based on domino hydroformylation/cyclization reactions

• Giuditta Guazzelli,
• Raffaello Lazzaroni and
• Roberta Settambolo

Beilstein J. Org. Chem. 2008, 4, No. 2, doi:10.1186/1860-5397-4-2

• remains a target compound for many research groups [4][5][6]. We recently reported the synthesis of Indolizidine 167B both in racemic and optically active form [7][8]; the crucial key was the cyclodehydration of 4-carboxyethyl-4-(pyrrol-1-yl)butanal, obtained via selective reduction of pyrrole masked

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