Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca

• Jeroen S. Dickschat,
• Hilke Bruns and
• Ramona Riclea

Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200

• –Emmons reaction gave the α,β-unsaturated ester 124d, which upon catalytic hydrogenation yielded 90. The synthetic compound was identical to the natural FAME as judged by mass spectrum and retention index (I = 1572). The retention index of this reference compound was used for to determine that Meγ = 51

• methyl 4,11-dimethyldodecanoate (110) from 24 by its reduction to the aldehyde 123a, Horner–Wadsworth–Emmons olefination to 124a, and catalytic hydrogenation (Scheme 3). The synthetic material was identical to the natural compound 110. A related group of compounds (Figure 3D, blue) proved to have very

• DIBAH to the aldehyde 123c, Horner–Wadsworth–Emmons olefination to 124c, and final catalytic hydrogenation afforded 112. The product exhibited the same mass spectrum and retention index (I = 1441) as the natural FAME. The slight deviations between the calculated and measured retention indices for

Reductive amination with zinc powder in aqueous media

• Giovanni B. Giovenzana,
• Daniela Imperio,
• Andrea Penoni and
• Giovanni Palmisano

Beilstein J. Org. Chem. 2011, 7, 1095–1099, doi:10.3762/bjoc.7.125

• first choice for NaBH(OAc)3 followed by the highly flammable tetrahydrofuran. Catalytic hydrogenation is an interesting alternative to modified borohydrides in terms of atom economy, but its application is unfortunately not general as many chemical groups must be avoided (e.g., double and triple bonds

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• quantitative yields, either by reduction with sodium borohydride, or by catalytic hydrogenation using platinum on carbon [33][34]. The pyrrolines can be aromatized either by a two step procedure (i) NBS bromination and (ii) dehydrohalogenation in basic medium [35][36][37], or by dehydrogenation with Pd/C [38

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• . The catalyst retained high activity for at least 8 h under neat conditions. Keywords: flow chemistry; hydrogenation; polysilane; palladium; reduction; Findings Catalytic hydrogenation is one of the most important methods for the reduction of C–C double and triple bonds, and other functional groups

• polymer-incarcerated (PI) catalysts, which have high catalytic activity without causing metal leaching [1]. Heterogeneous catalytic hydrogenation in a batch system has recently been applied to continuous flow hydrogenation systems for high-throughput synthesis [2][3][4][5][6][7][8][9][10]. There are

• several problems associated with conducting heterogeneous catalytic hydrogenation in a batch system. These include the necessity for filtration of hydrogen-saturated pyrophoric catalysts from flammable solvents, the possible requirement to use hydrogen gas under high pressure, difficulties in the re-use

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• % aqueous sulfuric acid a rearrangement to furnish a mixture of the 3- and 5-nitro derivatives occurs, which unfortunately at this stage, could not be separated by crystallisation. However, when this mixture was subjected to catalytic hydrogenation with Raney nickel a separable mixture of the corresponding

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• sulfonamide derivatives 12 by reducing the nitro group to an amino group by catalytic hydrogenation followed by treatment with an arylsulfonyl chloride (Scheme 4). Alternatively, 5-aminopyrazoles 17 containing a cyclohexylmethyl- or phenylmethyl- sulfonamido group at position-3 were prepared by treating β

Identification and synthesis of impurities formed during sertindole preparation

• I. V. Sunil Kumar,
• G. S. R. Anjaneyulu and
• V. Hima Bindu

Beilstein J. Org. Chem. 2011, 7, 29–33, doi:10.3762/bjoc.7.5

• Discussion During the catalytic hydrogenation of indole 15, formation of 0.5–1.0% of the des-chloro indole 17 is observed; the level is reduced to less than 0.1% during its isolation and purification. It is necessary to remove the impurity at this stage because after condensation with imidazolidinone 16, it

• )-impurity 21 (Scheme 4). The catalytic hydrogenation of indole 19 proved to be a difficult reaction as significant formation of the dehalogenated products was observed, repeated recrystallization from MeOH afforded pure indole 20. Since dehalogenation was observed during the platinum oxide reduction of the

A bivalent glycopeptide to target two putative carbohydrate binding sites on FimH

• Thisbe K. Lindhorst,
• Kathrin Bruegge,
• Andreas Fuchs and
• Oliver Sperling

Beilstein J. Org. Chem. 2010, 6, 801–809, doi:10.3762/bjoc.6.90

• mannoside 5, which can be prepared from mannose pentaacetate in three simple steps [26]. Catalytic hydrogenation led to the amine 6 [27], which was subjected to peptide coupling with N-Boc-protected pentaglycine (Gly5Boc) under standard reaction conditions (Scheme 1). This led to the N-Boc-protected

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

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

• activity [136]. Starting with the tricyclic ketone 181 [137][138] a low yielding bromination reaction was undertaken followed by an acetate displacement of the resulting α-bromoketone to give 182 (Scheme 50). The amine was introduced by formation of an oxime followed by catalytic hydrogenation in the

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens

• Kirsti Parikka and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2009, 5, No. 22, doi:10.3762/bjoc.5.22

• reduced AR, the lack of stereochemical control was of no consequence. Following the Wittig reaction, catalytic hydrogenation and demethylation gave AR and AR haptens in ca. 40% overall yield. The Wittig product 7b was a practical starting material for the C23 hapten (2d), for which commercial alkanal or

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• in the near future. Enantioselective addition of trimethylsilyl cyanide to benzaldehyde. Asymmetric catalytic hydrogenation in a falling-film microreactor. Aldol reaction catalyzed by 5-(pyrrolidine-2-yl)tetrazole. Enantioselective addition of diethylzinc to aryl aldehydes. Glyoxylate-ene reaction in

(−)-Complanine, an inflammatory substance of marine fireworm: a synthetic study

• Kazuhiko Nakamura,
• Yu Tachikawa and
• Daisuke Uemura

Beilstein J. Org. Chem. 2009, 5, No. 12, doi:10.3762/bjoc.5.12

• ) of both enantiomers are under consideration at the present time. In conclusion, (−)-complanine was successfully synthesized from (R)-malic acid by acetylene coupling and catalytic hydrogenation as key steps. The absolute configuration of the natural product was determined to be R. Experimental

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

• Sharpless AD and AE reactions (Scheme 35). Elongation of the carbon skeleton of 256 was achieved by a ring-opening reaction using 257 to afford alkyne 258. Then Wittig reaction of the corresponding Wittig reagent prepared from 258 with aldehyde 259 followed by catalytic hydrogenation and deprotection

• further elaborated to afford the epoxide 53. Next, the lithiated derivative of THF alkyne 22, which was prepared from the D-glucono-δ-lactone-derived α-hydroxyl ester 54 through Sharpless AD reaction as a key step, was treated with epoxide 53 in the presence of BF3·Et2O to afford alkynol 56. Catalytic

• hydrogenation of 56 and subsequent construction of the butenolide segment finished the total synthesis of annonacin (48), whose Rf value and spectroscopic data were identical to those reported for the natural product. In 2001, the full details of this total synthesis were reported [31]. Total synthesis of

Diastereoselective and enantioselective reduction of tetralin- 1,4-dione

• E. Peter Kündig and
• Alvaro Enriquez-Garcia

Beilstein J. Org. Chem. 2008, 4, No. 37, doi:10.3762/bjoc.4.37

• being the largely dominant species in solution [4]. Tetralin-1,4-dione (2) has also been obtained by catalytic hydrogenation of 1,4-naphthoquinone (3) using Wilkinson’s catalyst (70% yield) [5], by oxidation of 1-tetralone (4) with t-BuOOH and a dirhodium caprolactamate catalyst (27% yield at 29

New acylides: synthesis of 3-O-[γ-(4-oxo-2-aryl- thiazolidin- 3-yl)butyryl]erythromycin A derivatives

• Deepa Pandey,
• Wahajul Haq and
• Seturam B. Katti

Beilstein J. Org. Chem. 2008, 4, No. 14, doi:10.3762/bjoc.4.14

• upon treatment with methanol for several hours gave the desired 3-O-acyl derivative 2 in 72% yield after silica gel column chromatography. Compound 2 was subjected to catalytic hydrogenation using 10% Pd/C in methanol. The reaction was complete within 1 h as monitored by tlc. After usual work up the

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

• (−)-39 in 70% yield. In order to introduce the remaining stereogenic centres of the target system, the alkene bond of the bicyclic vinylogous urethane 39 needs to be reduced stereoselectively. Based on our previous success with the indolizidine analogue 19, we opted for catalytic hydrogenation, which is

• through bicyclic enaminone intermediates in which the alkene bond is located between the bridgehead position and the adjacent site, we have a convenient and dependable method for introducing the correct relative stereochemistry at these two sites by means of catalytic hydrogenation. However, the

Knorr- Rabe partial reduction of pyrroles: Application to the synthesis of indolizidine alkaloids

• Brendon S. Gourlay,
• John H. Ryan and
• Jason A. Smith

Beilstein J. Org. Chem. 2008, 4, No. 3, doi:10.1186/1860-5397-4-3

• -alkylindolizidines and the stereoselectivity obtained is opposite to that of catalytic hydrogenation. Conclusion An efficient stereoselective synthesis of indolizidine alkaloids has been developed from α-ketopyrrole intermediates using a modified version of Knorr and Rabe's pyrrole reduction. Background The Birch

• to the facile and rapid reaction of the α-ketopyrrole 8 we explored the potential tandem α-ketopyrrole reduction/catalytic hydrogenation as an alternative to catalytic hydrogenation. The catalytic hydrogenation of 5-substituted tetrahydroindolizidines proceeds with high diastereoselectivity [14][15

• as a 9:1 mixture of diastereomers. The volatility of the compound meant that for practical purposes it was isolated as the hydrochloride salt by adding concentrated HCl to the organic extract before evaporation. Catalytic hydrogenation of the hydrochloride salt of the pyrroline gave a corresponding

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• with one equivalent of stannic chloride resulted in the formation of 10 via the acyliminium ion intermediate 11. Subsequent oxidation of alcohol 10 with pyridinium dichromate, then catalytic hydrogenation (H2 over Pd/C) of ketone 12 induced hydrogenolysis of the CBz group, reduction of the double bond

• by reduction with LiAlH4 of indolizidinones 26. Access to (-)-dendroprimine by catalytic hydrogenation of indolizidinones 26. Synthesis of (±)-myrtine and (±)-epimyrtine. Enantioselective synthesis of (+)-myrtine and (-)-epimyrtine. Synthesis of (±)-lasubines I and II and (±)-2-epilasubine II

Diastereoselective synthesis of some novel benzopyranopyridine derivatives

• Pradeep K. Mohakhud,
• Sujeet M. R. Kumar,
• Vasanth M. R. Kumar,
• Ravi M. R. Kumar,
• Moses D. R. Babu,
• Vyas D. R. K and
• Om D. R. Reddy

Beilstein J. Org. Chem. 2006, 2, No. 25, doi:10.1186/1860-5397-2-25

• derivative was also obtained from the N-benzylated-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridine via catalytic hydrogenation. The resolution of the enantiomers was carried out using D-(-)-mandelic acid as chiral reagent. The absolute configuration of the S,S-mandelate salt

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• -difluorosuccinic acids 19. The preparation of stereoisomers of 2,3-difluorosuccinic acids, has involved conversions of tartaric acids (esters) [6][7], as described above in Scheme 1. Other approaches have involved the direct fluorination of fumaric acid [16] and the catalytic hydrogenation of 2,3-difluoromaleic

Multiple hydride reduction pathways in isoflavonoids

• Auli K. Salakka,
• Tuija H. Jokela and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2006, 2, No. 16, doi:10.1186/1860-5397-2-16

• isoflavans 9, which however are obtained by catalytic hydrogenation [10][16][20]). Incidentally, it is appropriate to point out that flavones do not undergo similar reductive metabolism in mammals as described above for isoflavones. We will nevertheless present at a later date certain findings on the hydride

• study clears this issue by 2D NMR work on a natural 2-isoflavene, [54] establishing that the H-2 and H-4 protons appear at δ 6.87 and 3.61, respectively, much as expected by correlation data shift calculations. Isoflavans (9) have not been prepared by hydride reductions, but by catalytic hydrogenation

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

• effectively be reduced using Pd(0)EnCat™ 30NP under conventional catalytic hydrogenation conditions of H2 (atmospheric pressure) with good selectivity and conversions [20]. Results and discussion The results obtained using different conditions for the carbonyl reduction of 4-methoxybenzaldehyde and 4