Wagner-Meerwein Rearrangement Research Articles

Stability of nicotinate and dodecyl sulfate in a Lewis acidic ionic liquid for aluminum electroplating and characterization of their degradation products.

Plating bath additives are essential for optimization of the morphology of electroplated layers. The ionic liquid 1-ethyl-3-methylimidazolium (EMIM) chloride plus 1.5mol equivalents of AlCl3 has great potential for electroplating of aluminum. In this study, the chemical and electrochemical stability of the additives EMIM-nicotinate and sodium dodecyl sulfate and their effect on the stability of EMIM was investigated and analyzed. Nicotinate and its electrochemical decomposition product β-picoline could be detected and we show with a single HPLC-UV-MS method that EMIM is not affected by the decomposition of this additive. An adapted standard HPLC-UV-MS method together with GC-MS and ion chromatography was used to analyze the decomposition products of SDS and possible realkylation products of EMIM. Several volatile medium and short chain-length alkanes as well as sulfate ions have been found as decomposition products of SDS. Alkenium ions formed as intermediates during the decomposition of SDS realkylate EMIM to produce mono- up to pentasubstituted alkyl-imidazoles. A reaction pathway involving Wagner-Meerwein rearrangements and Friedel-Crafts alkylations has been suggested to account for the formation of the detected products.

ChemInform Abstract: Enantioselective Ring Opening of meso‐Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N‐Oxides Fused with the Bicyclo[3.3.1]nonane Framework.

The synthesis of new chiral Lewis basic organocatalysts that contain pyridine N-oxide moieties fused with the bicyclo[3.3.1]nonane framework is reported. The obtained pyridine N-oxides were employed as catalysts in the enantioselective ring opening of meso-epoxides with silicon tetrachloride. Derivative 1b endowed with two 2,4-diaryl-substituted pyridine N-oxide moieties proved to be a particularly effective catalyst for desymmetrization of norbornene oxide 16i to furnish Wagner–Meerwein rearrangement product 20i in unprecedented 96 % ee. Difunctional congener 3, which is striped of the 4-aryl substituents, exhibited moderate to high levels of asymmetric induction (47–88 % ee) with alicyclic epoxide substrates.

Enantioselective Ring Opening of meso‐Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N‐Oxides Fused with the Bicyclo[3.3.1]nonane Framework

AbstractThe synthesis of new chiral Lewis basic organocatalysts that contain pyridine N‐oxide moieties fused with the bicyclo[3.3.1]nonane framework is reported. The obtained pyridine N‐oxides were employed as catalysts in the enantioselective ring opening of meso‐epoxides with silicon tetrachloride. Derivative 1b endowed with two 2,4‐diaryl‐substituted pyridine N‐oxide moieties proved to be a particularly effective catalyst for desymmetrization of norbornene oxide 16i to furnish Wagner–Meerwein rearrangement product 20i in unprecedented 96 % ee. Difunctional congener 3, which is striped of the 4‐aryl substituents, exhibited moderate to high levels of asymmetric induction (47–88 % ee) with alicyclic epoxide substrates.

Ab initio/GIAO-CCSD(T) (13)C NMR study of the rearrangement and dynamic aspects of rapidly equilibrating tertiary carbocations, C6H13(+) and C7H15(+).

The rearrangement pathways of the equilibrating tertiary carbocations, 2,3-dimethyl-2-butyl cation (C6H13(+), 1), 2,3,3-trimethyl-2-butyl cation (C7H15(+), 5) and 2,3-dimethyl-2-pentyl cation (C7H15(+), 8 and 9) were investigated using the ab initio/GIAO-CCSD(T) (13)C NMR method. Comparing the calculated and experimental (13)C NMR chemical shifts of a series of carbocations indicates that excellent prediction of δ(13)C could be achieved through scaling. In the case of symmetrical equilibrating cations (1 and 5) the Wagner-Meerwein 1,2-hydride and 1,2-methide shifts, respectively, produce the same structure. This indicates that the overall (13)C NMR chemical shifts are conserved and independent of temperature. However, in the case of unsymmetrical equilibrating cations (8 and 9) the Wagner-Meerwein shift produces different tertiary structures, which have slightly different thermodynamic stabilities and, thus, different spectra. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level structure 8 is only 90 calories/mol more stable than structure 9. Based on computed (13)C NMR chemical shift calculations, mole fractions of these isomers were determined by assuming the observed chemical shifts are due to the weighted average of the chemical shifts of the static ions.

ChemInform Abstract: Wagner—Meerwein Rearrangement of [3.3.1] Bicyclic N‐Boc Aminols: Vinyl Migration in Preference to Aryl Migration.

ChemInformVolume 46, Issue 14 Heterocyclic Compounds ChemInform Abstract: Wagner—Meerwein Rearrangement of [3.3.1] Bicyclic N-Boc Aminols: Vinyl Migration in Preference to Aryl Migration. Jian-Guo Fu, Jian-Guo Fu Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this authorRui Ding, Rui Ding Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this authorBing-Feng Sun, Bing-Feng Sun Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this authorGuo-Qiang Lin, Guo-Qiang Lin Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this author Jian-Guo Fu, Jian-Guo Fu Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this authorRui Ding, Rui Ding Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this authorBing-Feng Sun, Bing-Feng Sun Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this authorGuo-Qiang Lin, Guo-Qiang Lin Key Lab. Synth. Chem. Nat. Subst., Shanghai Inst. Org. Chem., Chin. Acad. Sci., Shanghai 200032, Peop. Rep. ChinaSearch for more papers by this author First published: 19 March 2015 https://doi.org/10.1002/chin.201514211Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume46, Issue14April, 2015 RelatedInformation

Atmospheric and high pressure ene reaction of norbornene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione

Thermodynamic and activation parameters (enthalpy, entropy, and volume) have been determined from the pressure and temperature dependences of the rate of the reaction of norbornene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione in toluene, which is accompanied by Wagner-Meerwein rearrangement. The enthalpy of the reaction in 1,2-dichloroethane has been determined by calorimetry. The obtained data correspond to a weakly polar transition state.

Unexpected methyl migrations of ethanol dimer under synchrotron VUV radiation.

While methyl transfer is well known to occur in the enzyme- and metal-catalyzed reactions, the methyl transfer in the metal-free organic molecules induced by the photon ionization has been less concerned. Herein, vacuum ultraviolet single photon ionization and dissociation of ethanol dimer are investigated with synchrotron radiation photoionization mass spectroscopy and theoretical methods. Besides the protonated clusters cation (C2H5OH)⋅H(+) (m/z = 47) and the β-carbon-carbon bond cleavage fragment CH2O⋅(C2H5OH)H(+) (m/z = 77), the measured mass spectra revealed that a new fragment (C2H5OH)⋅(CH3)(+) (m/z = 61) appeared at the photon energy of 12.1 and 15.0 eV, where the neutral dimer could be vertically ionized to higher ionic state. Thereafter, the generated carbonium ions are followed by a Wagner-Meerwein rearrangement and then dissociate to produce this new fragment, which is considered to generate after surmounting a few barriers including intra- and inter-molecular methyl migrations by the aid of theoretical calculations. The appearance energy of this new fragment is measured as 11.55 ± 0.05 eV by scanning photoionization efficiency curve. While the signal intensity of fragment m/z = 61 starts to increase, the fragments m/z = 47 and 77 tend to slowly incline around 11.55 eV photon energy. This suggests that the additional fragment channels other than (C2H5OH)⋅H(+) and CH2O⋅(C2H5OH)H(+) have also been opened, which consume some dimer cations. The present report provides a clear description of the photoionization and dissociation processes of the ethanol dimer in the range of the photon energy 12-15 eV.

Wagner–Meerwein rearrangement of [3.3.1] bicyclic N-Boc aminols: vinyl migration in preference to aryl migration

The Wagner–Meerwein rearrangement of [3.3.1] bicyclic N-Boc aminols was established, featuring the migration of the vinyl group instead of the aromatic ring. The structure of the rearrangement product was deduced through extensive spectroscopic studies and confirmed by the synthetic efforts. The scope of the reaction was examined and reasonably good yields were obtained for substrates with alkyl, allyl or benzyl substituent.

Reaction of Seleno‐ or Thiofenchone with Propiolic Acid: Wagner–Meerwein Rearrangement

ABSTRACTA reaction of selenofenchone with propiolic acid in refluxing chloroform produced 1,3‐oxaselenin‐6‐one, which further reacted with acid to afford the ring‐opened product. A reaction of 1,3‐oxathiin‐6‐one prepared from thiofenchone with trifluoroacetic acid gave a Wagner–Meerwein rearranged product. In the presence of AlCl3, thiofenchone reacted with methyl propiolate to afford the corresponding rearranged ester.

Lewis acid catalyzed cascade reaction to carbazoles and naphthalenes via dehydrative [3 + 3]-annulation.

A novel Lewis acid catalyzed dehydrative [3 + 3]-annulation of readily available benzylic alcohols and propargylic alcohols was developed to give polysubstituted carbazoles and naphthalenes in moderate to good yields with water as the only byproduct. The reaction was presumed to proceed via a cascade process involving Friedel-Crafts-type allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner-Meerwein rearrangement.

Generation of (+)‐Prezizanol, (+)‐Prezizaene, and the ent‐β‐Isopipitzol Framework via Cationic Rearrangement of Khusiol and Related Compounds

AbstractTreatment of the tosylate of khusiol with lithium carbonate in aqueous 1,4‐dioxane affords, via a Wagner–Meerwein rearrangement, (+)‐prezizanol. POCl3/pyridine‐mediated dehydration of (+)‐prezizanol then gives (+)‐prezizaene. More direct and efficient routes to this last compound were achieved by treating either khusiol or its C8 epimer with POCl3/pyridine. Under related conditions, a cyclic sulfate is converted, by a high yielding process, into an alcohol that embodies the decahydro‐1,7‐methanonaphthalene framework.

Synthesis of 1′-substituted 4′,4′-dimethyl-6′-methoxy-4′H-spiro[cyclohexane-1,3′-isoquinolines

The reaction of 1-(4-methoxyphenyl)-1-(1-methylcyclohexyl)ethanol with nitriles in concentrated sulfuric acid afforded 1′-substituted 6′-methoxy-4′,4′-dimethyl-4′H-spiro[cyclohexane-1,3′-isoquinolines] as a result of consecutive Wagner-Meerwein rearrangement and Ritter reaction.

An efficient approach to construct 2-arylbenzo[b]furans from 2-methoxychalcone epoxides

An efficient and practical method for construction of 2-arylbenzo[b]furans from 2-methoxychalcone epoxides has been reported. Catalyzed by 2 mol % of BF3·Et2O, 2-methoxychalcone epoxides went through the Meerwein rearrangement, followed by deformylation in one-pot to successfully afforded 2-methoxydeoxybenzoins. Afterward, 2-arylbenzo[b]furans were obtained in high yields (87%–100%) via intermolecular cyclodehydration of 2-methoxydeoxybenzoins with 48% HBr. By utilization of this approach, the natural product stemofuran A and the key intermediate of eupomatenoid 6 have been synthesized conveniently.

Structure elucidation of a new open chain isomer of the cannabimimetic cyclopropoylindole A-796,260

A new hitherto unknown ring opened isomer of the tetramethylcyclopropoylindole 1-(2-morpholin-4-ylethyl)-1H-indol-3-yl]-(2,2,3,3-tetramethylcyclopropyl)methanone (A-796,260) has been identified in a seizure of the German Customs. It bears an E-alkene moiety in the side chain with a tert.-butyl group, having a 3-penten-5-one skeleton. The isomer is not identical to the known products of thermal ring opening of tetramethylcyclopropoylindoles, which have a 1-pentene-5-one alkyl chain, instead. We postulate its formation via a Wagner–Meerwein-rearrangement under acidic conditions during the attempted synthesis of the desired tetramethylcyclopropoylindole. Whether the compound, found in high purity, has been the result of a synthesis fault or has been synthesized intentionally and if the new isomer has cannabimimetic potential, is still unknown. During structure elucidation with NMR spectroscopy and mass spectrometry, interesting phenomena have been detected concerning the product ion spectrometry of tetramethylcyclopropoylindoles.

Enantioselective Organocatalytic Iodination-Initiated Wagner–Meerwein Rearrangement

The present manuscript describes a high-yielding enantioselective semipinacol transposition, initiated by an electrophilic iodination event. The title transformation makes use of the anionic phase-transfer catalysis (PTC) paradigm for chirality induction. Thus, when combined appropriately, the insoluble cationic iodinating reagent S9 and the lipophilic phosphoric acid L9 act as an efficient source of chiral iodine that performs the semipinacol transposition of strained allylic alcohols A(x) to β-iodo spiroketones B(x) in good yields and with high levels of diastereo- and enantio-induction. The product β-iodo spiroketones could be derivatized stereospecifically and without stereoerosion, giving rise to products inaccessible directly from a semipinacol rearrangement.

Synthesis of novel 13α-18-nor-16-carboxamido steroids via a palladium-catalyzed aminocarbonylation reaction

13α-18-nor-16-Carboxamido steroids were synthesized via a palladium-catalyzed aminocarbonylation reaction of the corresponding iodoalkenes. The starting material was an unnatural 13α-16-keto steroid, obtained by a Wagner–Meerwein rearrangement of a 16α,17α-epoxide in the presence of [BMIM][BF4]. The 13α-16-keto steroid was converted to a mixture of 16-iodo-16-ene and 16-iodo-15-ene derivatives in two steps by Barton’s methodology. Aminocarbonylation of the steroidal alkenyl iodides was carried out using different primary and secondary amines as nucleophiles. The products, 16-carboxamido-16-ene and 16-carboxamido-15-ene derivatives, were obtained in good yields and were characterized by 1H and 13C NMR, IR and MS.The reduction of the above two unsaturated carboxamides resulted in the same product, 17α-methyl-16α-carboxamido-androstane.

ChemInform Abstract: Reagent Control of [1,2]‐Wagner—Meerwein Shift Chemoselectivity Following the Nazarov Cyclization: Application to the Total Synthesis of Enokipodin B (X).

ChemInform Abstract: Reagent Control of [1,2]‐Wagner—Meerwein Shift Chemoselectivity Following the Nazarov Cyclization: Application to the Total Synthesis of Enokipodin B (X).

ChemInform Abstract: Efficient Nazarov Cyclization/Wagner—Meerwein Rearrangement Terminated by a CuII‐Promoted Oxidation: Synthesis of 4‐Alkylidene Cyclopentenones.

ChemInform Abstract: Efficient Nazarov Cyclization/Wagner—Meerwein Rearrangement Terminated by a Cu^II‐Promoted Oxidation: Synthesis of 4‐Alkylidene Cyclopentenones.

Identification of a Fossil Sterane Biomarker in Crude Oil – an Androstane with a Modified Carbon Skeleton

AbstractThree constitutional isomers of androstane were prepared for comparison with three unknown fossil C19H32 organic biomarkers (“19A”, “19B”, and “19C” in elution order) in geological samples from Oman. 3β‐Methyl‐A‐nor‐androstane was prepared in six steps (8 % overall yield) from testosterone. The key steps of this sequence were an Eschenmoser fragmentation and recyclization of the A ring. A mixture of four stereoisomers of 3‐methyl‐A‐nor‐androstane (4 % overall yield) was prepared by ionic hydrogenation of the olefin after A‐ring recyclization in three steps. 17‐Methyl‐18‐nor‐androstane was synthesized in four steps as a mixture of isomers (58 % overall yield) from dihydrotestosterone with a Wagner–Meerwein shift of the 13β‐methyl group to C‐17 as the key step. Pure 17β‐ and 17α‐methyl‐18‐nor‐13α‐androstane (4 and 2 % overall yield, respectively) were obtained in three additional steps after α‐oxidation of the Wagner–Meerwein rearrangement product and subsequent reduction. The synthesis of 18‐nor‐D‐homo‐13β‐androstane (12 % yield over seven steps from dihydrotestosterone) involved oxidative cleavage of the C–C double bond in the Wagner–Meerwein rearrangement product from the previous synthesis and subsequent recyclization of the D ring followed by reduction. The relative configurations of all final products were confirmed by X‐ray crystallography. A comparison of the synthetic standards with the saturated hydrocarbon fraction of an Oman crude oil by gas chromatography (GC–MS) coinjection on three different GC columns and comparison of mass spectra revealed that unknown compound 19C is 18‐nor‐D‐homo‐13β,14α‐androstane, whereas the isomeric 3‐methyl‐A‐nor‐androstanes and 17‐methyl‐18‐nor‐androstanes elute close to 19A and 19B, respectively, but do not match the unknowns.

Synthesis of ent‐Kaurane and Beyerane Diterpenoids by Controlled Fragmentations of Overbred Intermediates

Efficient access to minimally oxidized members of the ent-kaurane and beyerane class of terpenes has been achieved by using a polyene cyclization precursor designed to directly yield oxidation at the axial C19-methyl group. Construction of the [3.2.1]bicyclic system found in the ent-kaurane skeleton was realized with two overbred intermediates. Wagner–Meerwein rearrangement of the [3.2.1]bicyclic system yields the beyerane skeleton of isosteviol.