Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• moderate yield of a new hydroperoxyacetal. The exchange reaction was observed in several solvents (e.g., CH2Cl2, 1,2-dichloroethane) but was most efficient in acetonitrile. The alkoxide exchange was accompanied by much slower exchange of the peroxide; for example, prolonged reaction (>24 h) of acetal 26 in

Controlled synthesis of poly(3-hexylthiophene) in continuous flow

• Helga Seyler,
• Jegadesan Subbiah,
• David J. Jones,
• Andrew B. Holmes and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2013, 9, 1492–1500, doi:10.3762/bjoc.9.170

• thiophene Grignard monomer 2 is prepared from the magnesium exchange reaction of an alkyl Grignard reagent and 2,5-dibromo-3-hexylthiophene (1, Scheme 1a). It should be noted here that a mixture of Grignard monomers 2a and 2b is produced in this step, typically in a ratio of 75:25. Only 2a participates in

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

• Martin Goez and
• Martin Vogtherr

Beilstein J. Org. Chem. 2013, 9, 1448–1454, doi:10.3762/bjoc.9.164

• on the reaction coordinate and, specific to this work, make the two sides of a self-exchange reaction distinguishable, as to allow one to measure its rate. Experimental All chemicals were commercially available. DES was purified by distillation, TPP+ and THTP were used as received, the solvent

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

• Neil Thomson,
• Alexander L. Kanibolotsky,
• Joseph Cameron,
• Tell Tuttle,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2013, 9, 1243–1251, doi:10.3762/bjoc.9.141

• ). However, although the conditions were unchanged, the halogen exchange reaction used to afford 10 was poorer yielding than that which produced 2. This was due to incomplete conversion from the bromide to the iodide. The inability to separate 9 and 10 meant that this mixture was not further purified, and

Intramolecular carbolithiation cascades as a route to a highly strained carbocyclic framework: competition between 5-exo-trig ring closure and proton transfer

• William F. Bailey and
• Justin D. Fair

Beilstein J. Org. Chem. 2013, 9, 537–543, doi:10.3762/bjoc.9.59

• -methylenebicyclo[2.2.1]heptane (8) was prepared as illustrated in Scheme 6 (for details, see Supporting Information File 1). Iodide 8 was converted to the corresponding alkyllithium by low temperature lithium–iodine exchange in n-C5H12/Et2O (9:1 v/v) following our general protocol [22]. The exchange reaction is

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

• Martin Goez,
• Isabell Frisch and
• Ingo Sartorius

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

• respective polarizations, and escape affords free radicals X• and Y• bearing polarizations of exactly the same magnitudes but opposite signs to the geminate ones, owing to the spin-sorting nature of the CIDNP effect. By an exchange reaction of the free radicals with surplus reactants, e.g., X• + X X + X

• reactions of organic compounds in polar solvents [48]. According to the Marcus theory [49], the free energy of activation of an electron-self-exchange reaction equals one quarter of the reorganization energy λ, which is the energy needed to distort the geometries of the reactants (inner reorganization

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• -exchange reaction between an arene and, most conveniently, either naphthalene–Cr(CO)3 complex or (MeCN)3Cr(CO)3 in which the chromium ligand is only weakly bound [14]; (b) simply heating the arene with hexacarbonylchromium in an inert solvent (Mahaffy–Pauson method) [15][16]. Method (a) has the

• disadvantage that the applied chromium complexes for the ligand exchange reaction are extremely sensitive toward oxidation, due to the weakly bound chromium. For method (b) high-boiling-point solvents, such as di-n-butylether, decalin or dioxane, can be used. The addition of THF to these solvents was shown to

• aglycon in order to avoid complexation of hexacarbonylchromium with the basic nitrogen atom. However, all attempts to convert 1l into the corresponding tricarbonyl(η6-pyridine)chromium complex failed. Attempts to prepare a chromium complex of 1l by a ligand exchange reaction with naphthalene–Cr(CO)3 or

Bromine–lithium exchange: An efficient tool in the modular construction of biaryl ligands

• Laurence Bonnafoux,
• Frédéric R. Leroux and
• Françoise Colobert

Beilstein J. Org. Chem. 2011, 7, 1278–1287, doi:10.3762/bjoc.7.148

• -, tri-, and even tetra-substituted ortho,ortho'-dibromobiphenyls [25][28][31][36][37][38]. These have the advantage that, by means of successive or simultaneous bromine–lithium exchanges, a huge panel of substituents can be introduced into the biphenyl backbone. The bromine–lithium exchange reaction is

• , was submitted to the bromine–lithium exchange reaction. When 2,2',6-tribromobiphenyl (1a) [28] was treated at −78 °C with BuLi and the intermediate aryllithium trapped with iodomethane, 2,2'-dibromo-6-methylbiphenyl (1b) was obtained in an excellent yield of 96%. Analogously, when benzenesulfonylazide

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

• iodine-) magnesium exchange reaction; the direct insertion of magnesium turnings in the presence of LiCl; the direct magneziation of heterocycles using TMPMgCl·LiCl (41). Due to the higher polarity of the carbon–magnesium bond, these heterocyclic organometallics are significantly more reactive than the

• aid of the mixed Li/Mg-reagent iPrMgCl·LiCl (64), an efficient exchange reaction is also effective with a wide range of aryl and heteroaryl bromides [31][32][33][35]. This reagent (64) is commercially available as an approx. 1 M THF solution from Chemetall GmbH [27]. Recently, we have applied this

• exchange reaction for the regioselective functionalization of quinolines. Thus, the 2,3-dibromoquinoline (65) is regioselectively converted to the 3-magnesiated quinoline derivative 66. Using the same exchange reagent, iPrMgCl·LiCl (64) and 2,4-dibromoquinoline (68), it is now possible to obtain the 4

Meta-metallation of N,N-dimethylaniline: Contrasting direct sodium-mediated zincation with indirect sodiation-dialkylzinc co-complexation

• David R. Armstrong,
• Liam Balloch,
• Eva Hevia,
• Alan R. Kennedy,
• Robert E. Mulvey,
• Charles T. O'Hara and
• Stuart D. Robertson

Beilstein J. Org. Chem. 2011, 7, 1234–1248, doi:10.3762/bjoc.7.144

• bimetallic alternatives to the customary homometallic reagents. As part of these innovations the zinc–hydrogen exchange reaction has undergone a significant revolution in recent times propelling it into the spotlight. Despite finding utility in various types of organic reaction [6], simple zinc reagents

Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl₃ promoted homocoupling

• Aiichiro Nagaki,
• Yuki Uesugi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2011, 7, 1064–1069, doi:10.3762/bjoc.7.122

• homocoupling of aryllithiums, and this enabled its integration with the halogen–lithium exchange reaction of aryl halides in a flow microreactor. This system allows the homocoupling of two aryl halides bearing electrophilic functional groups, such as CN and NO2, in under a minute. Keywords: homocoupling; iron

• –lithium exchange reaction. Methanol (neat, flow rate: 3.0 mL/min) was added in M2 ( = 500 μm) and the mixture was passed through R2 ( = 1000 μm, L = 50 cm) to protonate p-methoxyphenyllithium. The reactions were carried out with varying residence time in R1 (tR1: 0.2–6.3 s) and varying temperature (T: −78

• shown in Figure 2, the yield of the protonated product, anisole, depends on both T and tR1. The reaction at low temperatures (T < −48 °C) with short residence times (tR1 < 0.79 s) resulted in very low yields, because the Br–Li exchange reaction was not complete. The increase in T and tR1 caused an

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

• Kumaresh Ghosh and
• Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

• precipitated chloride salt was filtered, washed with water and dried (0.51 g, 64.4%). The compound 6 in MeOH was subsequently treated with aqueous NH4PF6 solution to carry out the anion exchange reaction. The solution was heated with stirring for 20 min until a precipitate appeared. Filtration of the

Halide exchanged Hoveyda-type complexes in olefin metathesis

• Julia Wappel,
• César A. Urbina-Blanco,
• Mudassar Abbas,
• Jörg H. Albering,
• Robert Saf,
• Steven P. Nolan and
• Christian Slugovc

Beilstein J. Org. Chem. 2010, 6, 1091–1098, doi:10.3762/bjoc.6.125

• ] rather than methanol were used as the solvents. The halogen exchange reaction proved rapid at room temperature and reached an equilibrium comprising of three different species within less than 1 h. The compounds were identified as the starting material 1, the desired product 2 (or 3), and a “mixed

Synthesis of unsymmetrically substituted biaryls via sequential lithiation of dibromobiaryls using integrated microflow systems

• Aiichiro Nagaki,
• Naofumi Takabayashi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2009, 5, No. 16, doi:10.3762/bjoc.5.16

• lithiation of dibromobiaryls using an integrated microflow system. These observations may open a new aspect of the synthesis of unsymmetrically substituted biaryls (Scheme 1), and herein we report full details of this study. Results and Discussion Br-Li Exchange Reaction of 2,2′-Dibromobiphenyl First, we

• focused on Br-Li exchange reaction of 2,2′-dibromobiphenyl (1) to generate (2-bromobiphenyl-2′-yl)lithium. It is known that Br-Li exchange reaction of 2,2′-dibromobiphenyl (1) gives a significant amount of dilithiated product in a conventional macrobatch system [55][56]. In order to confirm this, we

• reexamined the Br-Li exchange reaction of 1 with 1 equiv of n-BuLi in a conventional macrobatch reactor (Scheme 2). A hexane solution of n-BuLi was added dropwise (1 min) to a THF solution of 1 in a 20 mL round-bottomed flask at T °C (T = −78, −48, −27, 0, and 24) to generate (2-bromobiphenyl-2′-yl)lithium

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

Mechanistic aspects of the isomerization of Z-vinylic tellurides double bonds in the synthesis of potassium Z-vinyltrifluoroborate salts

• Hélio A. Stefani,
• Rafael C. Guadagnin,
• Artur F. Keppler,
• Giancarlo V. Botteselle,
• João V. Comasseto and
• Carlos A. Suganuma

Beilstein J. Org. Chem. 2008, 4, No. 9, doi:10.1186/1860-5397-4-9

• features of the transmetallation with complete retention of the original double bond geometry, we report herein the synthesis of potassium vinyltrifluoroborate salts by means of the Te-Li exchange reaction. To the best of our knowledge, this is the first reported preparation of potassium E

• spectra of DBNBS radical adducts obtained during the Te-Li exchange reaction. (A) EPR spectrum obtained after 1 min incubation of the reaction mixture with the DBNBS aqueous solution, (B) EPR spectrum obtained after 15 min incubation of the reaction mixture with the DBNBS aqueous solution; (○) DBNBS

• /•TenBu radical adduct and (•) transient DBNBS radical adduct. Representative EPR spectrum of DBNBS radical adducts obtained during the Li-Boron exchange reaction. EPR spectrum obtained after 15 min incubation of the reaction mixture with the DBNBS aqueous solution. Synthetic route used to prepare vinyl

Development of potential manufacturing routes for substituted thiophenes – Preparation of halogenated 2-thiophenecarboxylic acid derivatives as building blocks for a new family of 2,6-dihaloaryl 1,2,4-triazole insecticides

• John W. Hull Jr.,
• Duane R. Romer,
• David E. Podhorez,
• Mezzie L. Ash and
• Christine H. Brady

Beilstein J. Org. Chem. 2007, 3, No. 23, doi:10.1186/1860-5397-3-23

• the preparation of 23 could also be carried out from 22 via metallation with n-butyllithium in an ether solvent with sub-zero cooling, followed by quenching of the 2-thienyllithium species with CO2. We have found that the choice of solvent for the metal-halogen exchange reaction is important. Diethyl