Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• heterocycles (16 and 15 respectively), the latter reported here for the first time. The products arising from oxidative cleavage, the N-allylisatins, are diminished under these optimised conditions, and appear to arise only after longer reaction times. The proposed mechanism for the formation of spiro

• 1,3-rearrangement process. The N-allylisatins observed [4] are likely to be formed by oxidative cleavage processes as previously reported [4][11]. Control of the branch points in the overall base-catalysed cascade allylation reactions with indigo is clearly important in achieving practical synthetic

A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• attempts to remove the benzyl group under various catalytic hydrogenation conditions failed entirely. Cleavage of the DMB group with TFA [16] was also tried, but brought no success and extensive formation of polymerization products of the corresponding iminium ion was observed. Oxidative cleavage of the

Synthesis of the furo[2,3-b]chromene ring system of hyperaspindols A and B

• Danielle L. Paterson and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 265–270, doi:10.3762/bjoc.11.29

• product 19. Dihydroxylation of 19, followed by oxidative cleavage of the resultant diol gave aldehyde 20 in 80% yield over two steps. Addition of lithiate 16 to aldehyde 20 gave alcohol 21 in 87% yield as an inseparable 1:1 mixture of diastereoisomers. Hydrogenolysis of the benzyl ether in 21 gave ketal

Enantioselective synthesis of polyhydroxyindolizidinone and quinolizidinone derivatives from a common precursor

• Nemai Saha and
• Shital K. Chattopadhyay

Beilstein J. Org. Chem. 2014, 10, 3104–3110, doi:10.3762/bjoc.10.327

• oxidative cleavage of the vicinal diol unit in the latter to a formyl group (not isolated) followed by its in situ reduction with NaBH4 delivered the hydroxymethyl chain in 17. Hydrogenolytic removal of the two benzyl ether functionalities with Pearlman’s catalyst then afforded the tetrahydroxyindolizidine

Superoxide chemistry revisited: synthesis of tetrachloro-substituted methylenenortricyclenes

• Basavaraj M. Budanur and
• Faiz Ahmed Khan

Beilstein J. Org. Chem. 2014, 10, 2531–2538, doi:10.3762/bjoc.10.264

• ][11][12][13][14][15], hydrolysis and substitution reactions [16][17][18]. Filippo and co-workers [19][20][21][22] have extensively studied the substitution reactions of alkyl halides and tosylates; oxidative cleavage reactions and hydrolysis of esters. Frimer and co-workers [23][24] have studied its

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• prepared in excellent yield and ee by alkylation of carboxy-lactam 49 (see Scheme 11) [84]. Oxidative cleavage of the terminal double bond and subsequent reduction with LiAlH4 afforded N-benzylpiperidine-alcohol 56 [84]. Hydrogenolysis of the N-benzyl group and re-protection with di-tert-butyl dicarbonate

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

• tricarballylic acid (105). The latter fragment would be accessed by conjugate addition of the anion of phosphonamide 28c to tert-butyl sorbate (106) to give intermediate 107 followed by oxidative cleavage of the chiral auxiliary (Figure 5 and Scheme 13). The preparation of 107 was performed as previously

• addition of trimethylsilylcyanide to the formed Schiff-base provided aminonitrile 168 as the major diastereomer (dr 95:5). Oxidative cleavage of the phenylglycinol moiety with Pb(OAc)4 liberated the amino-functionality and hydrolysis of the amide and nitrile under acidic conditions finally gave DCG-IV (162

• diastereomer (Scheme 21). Conversion of tert-butyl ester 170 into aldehyde 171 by a two-step protocol was followed by condensation with (R)-α-phenylglycinol and treatment of the formed Schiff base with trimethylsilylcyanide to afford α-aminonitrile 172 as major isomer (dr > 4:1). Oxidative cleavage with Pb(OAc

Synthesis and bioactivity of analogues of the marine antibiotic tropodithietic acid

• Patrick Rabe,
• Tim A. Klapschinski,
• Nelson L. Brock,
• Christian A. Citron,
• Paul D’Alvise,
• Lone Gram and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2014, 10, 1796–1801, doi:10.3762/bjoc.10.188

• . Oxidative cleavage of the glycol with NaIO4 resulted in a β-ketoester aldehyde that upon treatment with silica gel underwent an intramolecular aldol condensation to a mixture of 10a and 11a that were separable by column chromatography. Oxidation with DDQ gave tert-butyl tropone-2-carboxylate (12a) that was

Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst

• Nathan J. Gesmundo and
• David A. Nicewicz

Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128

• to examine the scope of the reaction with respect to the diene structure. Miyashi’s 1,5-diene (2b; E1/2Ox = 1.22 V vs SCE [12]) afforded a 50% yield of the expected endoperoxide along with ~5% of a 1,4-dione, presumably from double oxidative cleavage of the 1,5-diene (Table 2, entry 1). Unfortunately

• , attempts to move away from 2b to less electron-rich dienes such as 2c, 2d and 2e (Table 1, entries 2–4), failed to produce any of the desired endoperoxide products and mainly oxidative cleavage adducts were observed. Given the lack of reactivity of this alkene substitution pattern, we turned our attention

• intermediate. The competing 6-endo cyclization mode and formation of distonic cation radical 9 ultimately provides access to the more stabilized cation radical 10, which undergoes oxidative cleavage to afford the corresponding α-allyl ketones (Scheme 4). In the absence of the geminal dimethyl group (2r, 2s

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• amounts of osmium tetroxide to obtain the vicinal diol 3 [27]. This intermediate was preparatively separated as a 60:40 (R/S) mixture of epimers at C10. The diol compound was subsequently oxidized with NaIO4 to the aldehyde 4 with simultaneous C–C bond breakage. According to the literature an oxidative

• cleavage on silica in a two-phase system led predominantly to the C3 epimer of the R configuration 90:10 (yield 93%) in a short reaction time [27]. In our case, when the reaction time was prolonged to 2 hours, the overall yield remained at the same level while the diastereoselectivity was reduced to 71:29

Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and its enantiomer: a non-proteinogenic amino acid segment of the linear pentapeptide microginin

• Rajendra S. Rohokale and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2014, 10, 667–671, doi:10.3762/bjoc.10.59

• methanol:ethyl acetate (3:2) at balloon pressure gave 4-heptyl-L-threose derivative 5a as a viscous oil in 99% yield [33]. Removal of the 1,2-acetonide group with TFA–water in 5a provided an anomeric mixture of the hemiacetal, which was directly subjected to oxidative cleavage by using sodium metaperiodate in

• -pentodialdo-1,4-furanose (3b) which was obtained from D-glucose in good yield as reported earlier [33]. Thus, the Wittig reaction of 3b followed by hydrogenation (10% Pd/C) gave 4-heptyl-D-threose derivative 5b (Scheme 3). Hydrolysis of 1,2-O-isopropylidene (TFA:H2O) followed by oxidative cleavage of the

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• piperidine cis-11c and its N-deprotected derivative were converted to (2S,3R)-3-hydroxypipecolic acid through protecting group manipulation and oxidative cleavage of the phenyl group with RuCl3 and NaIO4 [38][40]. Conclusion Herein we presented a highly stereodivergent (dr up to 19:1), scalable and practical

Decandrinin, an unprecedented C₉-spiro-fused 7,8-seco-ent-abietane from the Godavari mangrove Ceriops decandra

• Hui Wang,
• Min-Yi Li,
• Félix Zongwe Katele,
• Tirumani Satyanandamurty,
• Jun Wu and
• Gerhard Bringmann

Beilstein J. Org. Chem. 2014, 10, 276–281, doi:10.3762/bjoc.10.23

• shown in Figure 4. A plausible biogenetic precursor of decandrinin (1) might be the naturally more common β-diastereomer of 7,13-ent-abietadien-3-ol (2). Accordingly, its 3β-OH group would be oxidized to yield int A, whose C-9 would then be hydroxylated to afford int B. Oxidative cleavage at the ∆7,8

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

• 96, for which the yield and enantioselectivity was determined starting from 93. Standard functional group interconversion first provided exo-methylene 97, followed by ruthenium-catalyzed oxidative cleavage of the installed exo-methylene moiety [94] to give tricyclic ketone 98, which can be converted

• quarternary carbon center, the resulting amide cyclized during the purification on silica to give amide 174. Reduction of this amide to the aminal was followed by dehydration and Lemieux–Johnson [149] oxidative cleavage to give dialdehyde 175. The liberated alcohol moiety was reprotected, followed by cleavage

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• assembled from nine acetate units and glycine, respectively N-methylglycine derivative, which contributes both carbon atoms and the nitrogen to the skeleton of 210 (position 12 and 12a). The latter are uncommon starter units in a type II polyketide assembly line [160]. Upon oxidative cleavage of the D-ring

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

• triethylsilane and BF3·Et2O [53], affording 11. Oxidative cleavage of 11 with KMnO4/Bu4NBr [54] afforded iso-C12 acid 1. Alternatively, anti-Markovnikov hydration of 11, using I2/NaBH4 then hydrogen peroxide [55], afforded the alcohol 12, and oxidation of 12 with KMnO4/Bu4NBr afforded iso-C13 acid 2

• ] followed by Chugaev elimination afforded the terminal alkene 19. Oxidative cleavage of 19 using KMnO4/Bu4NBr [54] afforded iso-C16 acid 5. Reduction of 5 (BH3·Me2S) [59] afforded the alcohol 20 that when subjected to the same transformations as before, via the xanthate ester 21, delivered the terminal

• alkene 22. Finally, oxidative cleavage (KMnO4/Bu4NBr) [54] of 22 afforded iso-C15 acid 4. The iso-C18 7 and iso-C19 8 fatty acids were synthesized through similar approaches from the related C16 lactone hexadecanolide 23 [60] (Scheme 3). Reaction of 23 with methylmagnesium bromide afforded 24

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• material throughput. In order to proceed with the synthesis, we needed a more robust route, with the following criteria: (1) no protecting groups requiring oxidative cleavage, and (2) introduction of the C13 hydroxy group at an early stage. Iodocyclization approaches to epoxide In the preparation of model

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• decreased from 24.5 to 21.3%. Very recently NHPI was reported to catalyze selective transformations without requiring additional initiators. Jiao et al. described the catalyzed oxidative cleavage of C=C double bonds using molecular oxygen as the final oxidant [72]. Following this approach α-methylstyrene

• from N-alkoxyphthalimides. Visible-light/g-C3N4 induced metal-free oxidation of allylic substrates. NHPI/o-phenanthroline-mediated organocatalytic system. NHPI/DMG-mediated organocatalytic system. NHPI catalyzed oxidative cleavage of C=C bonds. Synthesis of hydrazine derivatives. Acknowledgements We

Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation

• Lynnie Trzoss,
• Jing Xu,
• Michelle H. Lacoske and
• Emmanuel A. Theodorakis

Beilstein J. Org. Chem. 2013, 9, 1135–1140, doi:10.3762/bjoc.9.126

• (0)-catalyzed carbomethoxylation [87][88][89][90] produced the desired C-ring lactone 20 in 61% yield. Epoxidation of the C-6/C-7 enone with NaOH/H2O2 followed by oxidative cleavage of the C-11 terminal alkene under OsO4/NaIO4 conditions [91][92] afforded the corresponding C-11 aldehyde. Exposure of

Development of peptidomimetic ligands of Pro-Leu-Gly-NH₂ as allosteric modulators of the dopamine D₂ receptor

• Swapna Bhagwanth,
• Ram K. Mishra and
• Rodney L. Johnson

Beilstein J. Org. Chem. 2013, 9, 204–214, doi:10.3762/bjoc.9.24

• accomplished by initial esterification of 33a and 33b, respectively, followed by oxidative cleavage of the double bond in each case with OsO4/NaIO4 [46]. An efficient and reproducible conversion of 33b into 34c was developed that consisted of the following three-step route: (1) benzyl ester formation, (2

• ) oxidative cleavage of the double bond with OsO4/NaIO4, and (3) hydrogenolysis of the benzyl ester [36][48]. Although the Seebach methodology provides a highly stereoselective way to α-alkylated prolines, there are several shortcomings to the originally developed protocols [47]. In the oxazolidinone

A Wittig-olefination–Claisen-rearrangement approach to the 3-methylquinoline-4-carbaldehyde synthesis

• Mukund G. Kulkarni,
• Mayur P. Desai,
• Deekshaputra R. Birhade,
• Yunus B. Shaikh,
• Ajit N. Dhatrak and
• Ramesh Gannimani

Beilstein J. Org. Chem. 2012, 8, 1725–1729, doi:10.3762/bjoc.8.197

• underwent Claisen rearrangement to give 4-pentenals 3a–h. Protection of the aldehyde group of the 4-pentenals as acetals 4a–h and subsequent oxidative cleavage of the terminal olefin furnished nitroaldehydes 5a–h. Reductive cyclization of these nitroaldehydes yielded the required 3-methylquinoline-4

• -carbaldehydes 6a–h in excellent yields. Therefore, an efficient method was developed for the preparation of 3-methylquinoline-4-carbaldehydes from o-nitrobenzaldehydes in a simple five-step procedure. Keywords: acetal; Claisen rearrangement; oxidative cleavage; ring-closure; Wittig olefination; Introduction

• unsuccessful. Subjecting these acetals to oxidative cleavage in aq THF furnished the aldehydes 5a–h in good yields (Table 1). The NMR of these aldehydes revealed them again to be a mixture of diastereomers, although they appeared to be homogeneous on TLC. Reductive cyclization of these nitroaldehydes furnished

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• fact, the furan ring can readily undergo oxidative cleavage under various conditions, thus providing an interesting route to carboxylates [35]. In the case of tpys, oxidation of the furanyl ring was performed by using potassium permanganate in a basic reaction medium, followed by acidification to

Directed aromatic functionalization in natural-product synthesis: Fredericamycin A, nothapodytine B, and topopyrones B and D

• Charles Dylan Turner and
• Marco A. Ciufolini

Beilstein J. Org. Chem. 2011, 7, 1475–1485, doi:10.3762/bjoc.7.171

• more electrophilic quinolyl ketone would direct an initial conjugate addition of the anion of a suitable cyanoacetamide to its own β-position. A particularly direct way to produce 41 seemed to be the oxidative cleavage of the furan ring in 42, which thus became the first subgoal of our study. In that

A straightforward approach towards combined α-amino and α-hydroxy acids based on Passerini reactions

• Ameer F. Zahoor,
• Sarah Thies and
• Uli Kazmaier

Beilstein J. Org. Chem. 2011, 7, 1299–1303, doi:10.3762/bjoc.7.151

• by chelated enolate Claisen rearrangement [22][23] or transition metal-catalyzed allylic alkylation of chelated enolates [24] and subsequent oxidative cleavage of the γ–δ-unsaturated amino acids obtained. Results and Discussion An alternative approach is based on regioselective ring opening of

Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• particular, water as a nucleophilic reagent has been used in the addition of alkynes and allenes [16][17][18]. In contrast, gold-catalyzed oxidation chemistry has been less well developed [25][26][27][28][29][30][31][32][33][34][35][36], although oxidative cleavage of carbon–carbon double bonds and carbon

• /hydration and oxidative cleavage of allenes to form α-diketones and aldehydes, and the synthesis of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine [45][46][47][48][49][50][51][52][53][54][55][56]. Results and Discussion Our initial

• of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine was achieved in high yields. This reaction appears to proceed via oxidation/hydration and oxidative cleavage of the allene, and investigations into the mechanism of this