Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• , Method A, see Supporting Information File 1 for full experimental data). It is clear, that the chemoselectivity of the cyclisation reaction directly correlates to the nature of the C=C bond of the substrate. Also, the configuration and the position of participating substituents have immense influence on

Selective allylic hydroxylation of acyclic terpenoids by CYP154E1 from Thermobifida fusca YX

• Anna M. Bogazkaya,
• Clemens J. von Bühler,
• Sebastian Kriening,
• Alexandrine Busch,
• Alexander Seifert,
• Jürgen Pleiss,
• Sabine Laschat and
• Vlada B. Urlacher

Beilstein J. Org. Chem. 2014, 10, 1347–1353, doi:10.3762/bjoc.10.137

• YX that enables this type of oxidation. Several acyclic terpenoids were tested as possible substrates for CYP154E1, and the regio- and chemoselectivity of their oxidation was investigated. Using a previously established bioinformatics approach we identified position 286 in the active site of CYP154E1

• which is putatively involved in substrate binding and thereby might have an effect on enzyme selectivity. To tune regio- and chemoselectivity of the enzyme three mutants at position 286 were constructed and used for substrate oxidation. All formed products were analysed with GC–MS and identified using

• chemoselectivity [19]. The E-isomer geranylacetone was converted with a mutant of CYP102A1 from Bacillus megaterium (also referred to as P450 BM-3) with high activity and enantioselectivity to a single product 9,10-epoxygeranylacetone, while the oxidation of the Z-isomer nerylacetone yielded a mixture of several

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• changes in conversion and chemoselectivity. The formation of formaldehyde as the final oxidation product was proven qualitatively (colorless precipitation of polyformaldehyde was observed in most experiments) and by a GC–MS online detection of monomeric formaldehyde. From these results, we reasoned that

• comparison with optimized homogeneous conditions for model process. Chemoselectivity modification by application of a dilution effect. Supporting Information Supporting Information File 200: Experimental part.

Regioselective S_N2' Mitsunobu reaction of Morita–Baylis–Hillman alcohols: A facile and stereoselective synthesis of α-alkylidene-β-hydrazino acid derivatives

• Silong Xu,
• Jian Shang,
• Junjie Zhang and
• Yuhai Tang

Beilstein J. Org. Chem. 2014, 10, 990–995, doi:10.3762/bjoc.10.98

• reaction exhibited poor chemoselectivity which gave comparable yields of tri- and tetrasubstituted hydrazines. For example, the reaction of MBH acetate 1a' with diisopropyl azodicarboxylate (2a) and PPh3 afforded hydrazines 3a and 4a in 51% and 46% yields, respectively. Inspired by this report, and a

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• several drawbacks such as toxic reagents, harsh conditions, low yields, and low chemo- and regioselectivity. Hence, the development of an environmentally friendly methodology for the bromination of phenols with high chemoselectivity under mild and operationally simple conditions is still appealing

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• just perfectly suited for undergoing a 1,5-sigmatropic H-shift, giving directly rise to the formation of the conjugated push–pull triene 10. This mechanistic rationale suggests that the observed remarkable chemoselectivity in the formation of two different triene merocyanines could originate from

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• the heteroatom-containing, crown ether ring systems. A notable feature of these reactions is their remarkable chemoselectivity. Alternative pathways initiated by intramolecular SET from the carbamate nitrogen donor sites [57] to the phthalimide acceptor moiety excited state, even though

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

• secondary OH group proceeded (with PPh3 and P(OEt)3) in very high chemoselectivity most likely due to steric effects. The corresponding aziridine of 9a clearly resulting from activation of the secondary hydroxy group and subsequent fast 3-exo-trig cyclisation was only obtained as a sideproduct at higher

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• addition of carbamates, sulfonamides and imidazolidinones to linear and cyclic dienes 17 in the presence of catalytic amounts of PPh3AuOTf (Scheme 6). The method featured excellent 1,2-regioselectivity and high chemoselectivity, providing protected allylamines 18, in good yields, using nearly equimolar

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• Pleurotus sapidus. This ‘’mushroom catalysis’’ is operationally simple and allows the conversion of various unsaturated spirocyclic terpenoids. A number of new spirocyclic enones have thus been obtained with good regio- and chemoselectivity and chiral separation protocols for enantiomeric mixtures have been

• , alternative oxidation pathways cannot be ruled out for other substrates. Reviewing the available examples for PSA-mediated conversions in the literature, the regio- and chemoselectivity of these oxidations seems to be determined by the radical mechanism of the reactions and would thus follow well-established

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• having some distinct properties like high activity, high stereo-, regio- and chemoselectivity and high substrate specificity, which allow their use in a complex synthesis in a green and clean manner [1]. Recently, enzymes have received much attention for making processes more economically and

Gold-catalyzed glycosidation for the synthesis of trisaccharides by applying the armed–disarmed strategy

• Abhijeet K. Kayastha and
• Srinivas Hotha

Beilstein J. Org. Chem. 2013, 9, 2147–2155, doi:10.3762/bjoc.9.252

• glycoconjugates [24], carbohydrate epitopes present on the cell surface of infectious bacteria [25], glycopolypeptides [26], glycopolyacrylates [27], and glycomimetics [28]. The remarkable reactivity and chemoselectivity have also attracted other groups to investigate gold catalysts for glycosidation [29][30][31

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• :1 (Scheme 7). The less polar 22a was confirmed by X-ray diffraction [58]. The second alkene was further dioxygenated by repeating the previous protocol to deliver 23 with a 3/1 diastereoselectivity from 22b. The encountered poor chemoselectivity under conventional metal-mediated conditions for the

• preferentially underwent cyclization to deliver a variety of 3-susbtituted-γ-lactones (25b–d). For comparison, the mCPBA-epoxidation approach in literature always demonstrated that electron-rich alkenes are more reactive leading to the reversal of chemoselectivity [70][71]. A cyclopropane group was also

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• excellent enantioselectivities (70–97% ee, mostly above 90% ee) were achieved for different tetrahydroquinoline products 16 having gem-methyl ester groups (Scheme 12). For substrates containing one N-benzyl group and one N-ethyl group, binaphthol-based catalyst 17 was used; however, no chemoselectivity (16j

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

• –c to LiAlH4 in THF followed by quenching and treatment with HCOOH, spirocycles 11a–c were obtained in good yields. The chemoselectivity of the reduction was unambiguously confirmed by single-crystal X-ray diffraction studies of 11c. Furthermore, the use of an excess of DIBAL at room temperature

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• . It is therefore interesting to gather information about the chemoselectivity of these reactive intermediates. For intramolecular reactions, the ring size of the products can make an additional contribution to the observed chemoselectivity. In this study, we have addressed the competition between two

On the control of secondary carbanion structure utilising ligand effects during directed metallation

• Andrew E. H. Wheatley,
• Jonathan Clayden,
• Ian H. Hillier,
• Alison Campbell Smith,
• Mark A. Vincent,
• Laurence J. Taylor and
• Joanna Haywood

Beilstein J. Org. Chem. 2012, 8, 50–60, doi:10.3762/bjoc.8.5

• solvent or additives to influence the chemoselectivity of lithiation, 6-H was treated at −78 °C with t-BuLi in a hydrocarbon medium to which 1 equiv of PMDTA had been added. The resulting dark purple solution was transferred directly to a freezer (−30 °C) whereupon storage afforded a product that X-ray

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• , whereas lower values, around 0.13–0.21 mmol·h−1, were achieved in DCM. More interestingly, in all cases the conversion, chemoselectivity, selectivity and enantioselectivity were comparable or slightly superior to those found for the work under batch conditions with the same catalysts. The results obtained

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• -coupling (Negishi reaction) affords the 5-arylated furan 15 in 89% yield. Interestingly, a high chemoselectivity is observed with several heterocyclic dihalides [8][9]. Thus, the tribromopyrimidine 16 provides only the 4-zincated pyrimidine 17. After allylation, the expected allylated pyrimidine 18 is

• -iodide, and therefore facilitates the cleavage of this carbon–iodide bond. This method has been extended to the preparation of benzylic zinc reagents [13]. A remarkable chemoselectivity is observed and functional groups, such as an acetyl group, are perfectly compatible with such synthesis. Thus, the

• of the base, the role of MgCl2 is to increase its reactivity and the role of zinc is essential since it confers to this base an exceptional chemoselectivity (Scheme 8). Thus, the 1,3,4-oxadiazole 43 is readily converted to the zinc reagent 44 by the reaction with TMP2Zn·2MgCl2·2LiCl (42, 0.55 equiv

Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

• Michel Chiarucci,
• Mirko Locritani,
• Gianpiero Cera and
• Marco Bandini

Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139

• confirms the allylic SN1 mechanism for the present methodology [44]. The high chemoselectivity guaranteed by the gold catalysts is worthy of note, as it channels the reaction toward the allylic alkylation mechanism without any contamination deriving from transesterification reactions. This evidence is

Evaluation of a commercial packed bed flow hydrogenator for reaction screening, optimization, and synthesis

• Marian C. Bryan,
• David Wernick,
• Christopher D. Hein,
• James V. Petersen,
• John W. Eschelbach and
• Elizabeth M. Doherty

Beilstein J. Org. Chem. 2011, 7, 1141–1149, doi:10.3762/bjoc.7.132

• ]. In addition, the contamination appears to accumulate through continued use of the reactor, presenting a signficant challenge with regard to performance stability. It should be noted that after thorough decontamination of the reactor we were able to reproduce the high chemoselectivity observed in the

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

• benzaldehyde with aliphatic amines (entries e and f). The reaction with allylamine allows us to appreciate the chemoselectivity of this protocol, leaving the C=C double bond untouched. Entries g and h rely on the combination of aliphatic substrates; the yields are lower and coupling byproducts were not

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides

• Oksana Shvydkiv,
• Kieran Nolan and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121

• thiazolidine ring gave two sets of doublets at 2.97/3.39 ppm and 4.36/4.93 ppm. The increased yield of 7 compared to its carbon-analogue 3 suggests that the sulfur-atom in α-position to the carboxylate group in 6 accelerates photodecarboxylation [44][45]. In addition to the high chemoselectivity, DMBP remained

Triazole–Au(I) complex as chemoselective catalyst in promoting propargyl ester rearrangements

• Dawei Wang,
• Yanwei Zhang,
• Rong Cai and
• Xiaodong Shi

Beilstein J. Org. Chem. 2011, 7, 1014–1020, doi:10.3762/bjoc.7.115

• Dawei Wang Yanwei Zhang Rong Cai Xiaodong Shi Department of Chemistry, West Virginia University, Morgantown, WV 26506, USA 10.3762/bjoc.7.115 Abstract Triazole–Au (TA–Au) catalysts were employed in several transformations involving propargyl ester rearrangement. Good chemoselectivity was observed

• . Keywords: allene; chemoselectivity; gold catalysis; ligand effect; organometallic; Introduction The past decade has seen rapid growth in the use of homogeneous gold catalysis for conducting powerful organic transformations [1][2][3][4][5][6][7][8][9]. Like many other transition metal complexes, the

• indicating excellent chemoselectivity of the triazole coordinated gold complexes. Various propargyl esters were synthesized to test the reaction substrate scope. The results are summarized in Table 1. As shown in Table 1, the transformation proceeded smoothly with substrates having both an aromatic group on