bluuebunny/crossref_metadata_2025_split huggingface dataset:
The crystal and molecular structure of 3,4‐dihydro‐benzo(a)‐4‐ortho‐hydroxyphenyl‐3,4a‐diazo‐carbazole dimethylamino‐methanal, C20H15N3O. C3H7N O
Authors: Garcia‐Blanco S. , Beurskens Gezina , Beurskens Paul T. 
Published: September 2010

AbstractThe structure of the title compound, C20H15N3O. C3H7N O was determined by X‐ray analysis at T= 298 K, Mr=386.452, monoclinic, space group Cc, a=14.747(1), b=9.860(1), c=13.973(1) Å, β=91.21(1)°, V=2031.3(3) Å3, Z=4, F000=816, Dc=1.264 Mg/m3, CuKα radiation (graphite crystal monochromator, λ=1.5418 A), μ(CuKα)=6.301 cm‐1. The structure was solved by orientation and translation search on a known fragment and expanded with DIRDIF. Final conventional R‐factor=0.092, Rw=0.108 for 1522 unique reflections and 284 variables.
A new approach to annelated furans. The total synthesis of (±)‐euryfuran
Authors: Jansen B. J. M. , Peperzak R. M. , de Groot Ae. 
Published: September 2010

AbstractA new approach to annelated furans has been developed starting from ketones. Formylation of the enolate, protection of the aldehyde function as its (phenylthio)‐ or (n‐butylthio)methylene derivative and addition of methoxy(phenylthio)methyllithium gave adducts with the necessary functionalized carbon atoms. Rearrangement of these adducts to phenylthio aldehydes, followed by reduction, led to alcohols which spontaneously cyclized to furans. The method has been demonstrated in the total synthesis of (±)‐euryfuran. An unusual rearrangement was found upon hydrolysis of the adducts mentioned above in that a ring expansion leading to γ‐oxo α,β‐unsaturated aldehydes was observed.
Attempted synthesis of a [5](2,5)pyridinophan‐6‐one from its Dewar isomer
Authors: Kostermans G. B. M. , de Wolf W. H. , Bickelhaupt F. , Krever M. 
Published: September 2010

AbstractThe 1,4‐pentamethylene Dewar pyridone 1a was synthesized from 2,9‐undecadiyne (3), aluminium trichloride and phenyl isocyanate. The exclusive formation of 1a at the expense of other possible isomers is discussed and tentatively explained by the regiospecific reactivity of the intermediate 4a. Attempts to convert 1a into the [5] (2,5)pyridinophan‐6‐one 2 by irradiation, thermolysis or acid catalysis did not give the desired result. However, on thermolysis and acid catalysis, 1a rearranges to the ortho‐annelated pyridone 13 in high yield, the structure of which was established by X‐ray‐crystal structure determination. The mechanism of these reactions is discussed.
Synthesis of ribonucleoside 3′,5′‐cyclic phosphorothioates using a modified hydroxybenzotriazole phosphotriester approach
Authors: de Vroom E. , van der Marel G. A. , van Boom J. H. 
Published: September 2010

AbstractPhosphorothioylation of 3′,5′‐dihydroxyl ribonucleosides with O‐(2‐chlorophenyl) O, O‐bis[6‐(trifluoromethyl)‐1‐benzotriazolyl] phosphorothioate, followed by addition of N‐methyl‐imidazole and removal of protecting groups, gives ribonucleosides 3′,5′‐cyclic phosphorothioates. The latter compounds could also be prepared by phosphorothioylation of 2′,3′,5′‐trihydroxyl ribonucleosides.
Physico‐chemical studies on calcium soaps
Authors: Mehrotra K. N. , Upadhyaya S. K. 
Published: September 2010

AbstractCalcium soaps were prepared by the metathesis of the corresponding potassium soap with an aqueous solution of calcium acetate. The IR results showed that the fatty acids exist in a dimeric structure as a result of hydrogen bonding between the carboxyl groups of two acid molecules, whereas calcium palmitate has an ionic character. The X‐ray analysis indicated that the zig‐zag chains of the fatty acid radical constituent of the soap molecules extend straightforward on both sides of each basal plane and that the molecular axes of the soaps are slightly inclined to the basal plane. The thermal decomposition of calcium palmitate was found to be kinetically of zero order and the energy of activation for the decomposition reaction was in the region of 3 KJ/mole.
A new model for coenzyme B12
Authors: van Arkel B. , van der Baan J. L. , Balt S. , de Bolster M. W. G. , van Delft R. J. , Klumpp G. W. , de Koning H. , van den Winkel Y. 
Published: September 2010

AbstractA new cobaloxime‐type model for coenzyme B12 has been synthesized. For this model strong steric repulsion between its dioxymethylene bridge and (one of) the axial ligands on cobalt presages enhanced rates of axial ligand exchange.
The stereoselective synthesis of substituted 1‐hydroxyazetidines
Authors: van Elburg Paulus A. , Reinhoudt David N. , Harkema Sybolt 
Published: September 2010

AbstractThe four‐membered cyclic nitrones (2,3‐dihydroazete l‐oxides) 1a‐d and 2a‐c react with a variety of nucleophiles by stereoselective addition to the nitrone moiety. Reaction of the nitrones 1 and 2 with alkyl‐, allyl‐, benzyl‐, and arylmagnesium halides yields the l‐hydroxyazetidines 3, 4, 5, and 6, with the nucleophile adding from the less hindered side of the molecule. The keto nitrone 1b reacts with potassium cyanide to give the l‐hydroxyazetidine 4f. Reduction of nitrone 1b to give the l‐hydroxyazetidines 7 and 8 is achieved by reaction with lithium aluminum hydride at 0°C and at room temperature, respectively. In contrast, nitrone 1d reacts with lithium aluminum hydride only at 45°C to give the l‐hydroxyazetidine 11. The differences in the reactivity of the nitrones 1 and 2 towards nucleophilic reagents are explained in terms of steric hindrance in the addition step. Oxidation of the l‐hydroxyazetidine 3b with lead(IV) oxide affords the 2,3‐dihydroazete l‐oxide 15. Reduction of nitrone 15 with sodium borohydride affords the 1‐hydroxyazetidine 16, the epimer of compound 3b. Reaction of l‐hydroxyazetidine 3d with PbO2 yields the dimeric structure 17. Nitrone 1a reacts with the sodium salt of nitromethane to yield the l‐hydroxyazetidine 12. Keto nitrone 1b reacts with 4‐nitrobenzaldehyde in the presence of a catalytic amount of potassium hydroxide to give the 4‐benzylidene‐2,3‐dihydroazete l‐oxide 13. Upon prolonged reaction, nitrone 13 isomerizes to oxime 14, probably by an electrocyclic ring opening of an intermediate l‐hydroxy‐1,2‐dihydroazete.
Synthesis of three isotopomers of L‐tryptophan via a combination of organic synthesis and biotechnology
Authors: van den Berg E. M. M. , Baldew A. U. , de Goede A. T. J. W. , Raap J. , Lugtenburg J. 
Published: September 2010

AbstractIn this paper, we report the preparation of three isotopomers of L‐tryptophan on a gram scale, specifically labelled with 99% 15N (position 1) and 99% 13C (position 2) in the indole ring; for position 3, the incorporation was 90% 13C. The isotopically enriched indoles were synthesized from H15NO3, K13CN and 13CH3CN and then converted, with L‐serine, into the correspondingly labelled L‐tryptophans using genetic manipulated E. coli bacteria, which contain high amounts of the enzyme tryptophan synthetase. The 13C‐13C, 13C‐1H, 13C‐15N and 15N‐1H coupling constants of the indoles and the tryptophans were determined from the 1H NMR and 13C NMR spectra.
Synthesis and conformational analysis of phosphorus‐derivatized no‐base analogues of 3′, 5′ ‐cyclic nucleotides
Authors: Hermans Rob J. M. , Buck Henk M. 
Published: September 2010

AbstractA number of epimeric pairs of 3‐X‐3‐oxo‐trans‐2, 4, 7‐trioxa‐3‐phosphabicyclo[4.3.0]‐nonanes [5, X  OCH3; X  OPh; 7, X  Cl; 8, X  N(CH3)2; 9, X  S−; 10, X  O−] have been prepared as no‐base analogues of 3′,5′‐cyclic nucleotides. 1H NMR analysis shows the phosphate ring of the cis diastereomers (relationship of singly bonded substituent on phosphorus and proton H1) 5a–7a, 9a and 10 and the trans diastereomers 8b and 9b to be in the chair conformation 15. The phosphate rings of the epimers 5b–7b and 8a exist as an equilibrium between chair conformation 15 and twist conformation 16. The mole fraction of twist depends on the nature of the singly bonded substituent and varies from about 0.3 for 5b to 0.8 for 7b. The close similarity in coupling constants of the tetrahydrofuran ring of the phosphates 5–10 indicates that the population of a twist conformer has little effect on the conformation of this ring, which is close to 4E‐4T3. The results obtained for 5–10 are compared with those of conformational studies on corresponding phosphates derived from thymidine and cyclopentane.
Theoretical and molecular modelling studies on organic transition metal complexes. III. Calculation of the conformational energies of transition‐metal dichloro‐bis(pyridine) complexes using an extended CNDO/2 method
Authors: Morley John O. 
Published: September 2010

AbstractCalculations are reported on the conformational energies of the dichloro‐bis(pyridine) complexes of zinc, copper, nickel and cobalt. Results based on experimental geometries show that the tetrahedral conformer of the zinc complex is favoured over the corresponding square‐planar structure in line with experimental data, but the latter is preferred for the copper complex though the energy differences between both conformers is small. Square‐planar conformations are predicted for the nickel and cobalt complexes.
Sulfonation and sulfation in the reactions of the chloro‐ and dichlorophenols, 3‐fluorophenol and (2,3‐, 2,4‐ and 3,4‐dichlorophenoxy)acetic acid with concentrated aqueous sulfuric acid and sulfur trioxide
Authors: de Wit Peter , Cerfontain Hans 
Published: September 2010

AbstractThe chloro‐ and dichlorophenols have been sulfonated with sulfuric acid and with SO3 in aprotic solvents. In the sulfonations with concentrated aqueous sulfuric acid, the sulfonic acid isomer distribution is determined mainly by the ortho‐ and para‐directing and activating effect of the hydroxy substituent; this is also the determining factor in the aprotic sulfonations using up to 1.0 equiv of SO3. Upon using larger amounts of SO3, the sulfonation isomer distribution is increasingly determined by additional sulfonation of the corresponding phenyl hydrogen sulfate, of which the ‐OSO3H substituent is deactivating and mainly para‐ (and further ortho‐) directing.The sulfuric acid sulfonation of (2,3‐, 2,4‐ and 3,4‐dichlorophenoxy)acetic acid leads to the exclusive formation of the 4‐, 6‐ and 6‐sulfonic acid, respectively.
A spectroscopic study of the interaction between lanthanide ions and their surroundings in lanthanide magnesium nitrate hydrate (Ln2Mg3(NO3)12· 24H2O)
Authors: Blasse G. , Dirksen G. J. , van Vliet J. P. M. 
Published: September 2010

AbstractThe absorption and emission spectra of the mixed nitrates Ln2Mg3(NO3)12·24H2O (Ln = La, Ce, Eu, Gd) are reported. The interaction between the 4f electrons of the Ln3+ ion and the nitrate group is unexpectedly strong. This is apparent from a strong additional absorption in the case of Ce3+ and strong cooperative vibronic emission and absorption lines in the case of Eu3+.
Preparation and reactions of a disilyne synthon, 7,7′‐bis(7‐methyl‐1,4,5,6‐tetraphenyl‐7‐sila‐2,3‐benzo‐norbornadiene)
Authors: Sekiguchi Akira , Zigler Steven S. , Haller Kenneth J. , West Robert 
Published: September 2010

AbstractThe title compound (2) was prepared by condensing a bis(silole) 1 with benzyne. Thermolysis of 2 in the presence of anthracene, 9,10‐dimethylanthracene (DMA), 2,3‐dimethylbutadiene, and two acetylenes is described in detail. X‐ray structures for the anthracene and DMA adducts are reported.
Mixed platinum‐gold clusters. Synthesis, structure and properties of PtAu8(PPh3)8(NO3)2
Authors: Bour J. J. , Kanters R. P. F. , Schlebos P. P. J. , Steggerda J. J. 
Published: September 2010

AbstractPtAu8(PPh3)8(NO3)2 is formed by the reaction of H2 with Au(PPh3)NO3 and either Pt(PPh3)3 or Pt(COD)(NO3)2. The metal frame is a centred crown, with a phosphine bonded to each peripheral metal atom. 31P NMR and Mössbauer spectroscopy showed that Pt is in the centre and that the 8 Au atoms are on the crown. A FAB mass spectrum confirmed the indicated composition and showed that no hydrides are present. In an electrochemical study, the cluster could be reduced in two reversible one‐electron steps at ‐1.14 and ‐1.29 V vs SSCE. The growth of the PtAun clusters is discussed in terms of oxidative addition of H2 to Pt and electrophilic substitution of AuPPh3+.
X‐Ray crystal structure of the ethylzinc enolate of 1‐(2,4‐cyclopentadienyl)‐2‐(diethylamino)‐1‐ethanone, the unexpected reaction product from cyclopentadienyl(ethyl)zinc and ethyl N,N‐diethylglycinate
Authors: Jastrzebski Johann T. B. H. , Boersma Jaap , van Koten Gerard , Smeets Wilberth J. J. , Spek Anthony L. 
Published: September 2010

AbstractReaction of cyclopentadienyl(ethyl)zinc with ethyl N,N‐diethylglycinate affords the dimeric ethylzinc enolate (2) of 1‐(2,4‐cyclopentadienyl)‐2‐(diethylamino)‐1‐ethanone in quantitative yield. Its molecular structure was determined by X‐ray crystallography. Crystals of 2 C26H42N2O2Zn2 are monoclinic, space group P21/c, with unit cell parameters a = 7.972(1) Å, b = 15.741(2) Å, c = 11.062(2) Å, β = 91.85(2)°. The crystal structure was solved using standard Patterson methods (Zn) and subsequent difference Fourier techniques. Anisotropic full‐matrix least‐squares refinement with 1989 observed reflections and 160 parameters converged at R = 0.0335.
C‐Stannylated carbohydrate derivatives. Part 1. 6‐Deoxy‐1,2‐O‐isopropylidene‐6‐(triorganostannyl)‐α‐D‐glucofuranose
Authors: Taylor Oonah J. , Wardell James L. 
Published: September 2010

AbstractThe synthesis of 6‐deoxy‐1,2‐O‐isopropylidene‐6‐(triorganostannyl)‐α‐D‐glucofuranose (4) is reported. Compound 4a (R = R′ = Me), reacts with halogens (I2 and Br2) or with Pd(COD)CI2 to give 4 (R = Me, R = X (X = I, Br or Cl) and MeY [Y = I, Br or Pd(CODCl]. The unsaturated sugar, 5,6‐dideoxy‐l,2‐O‐isopropylidene‐α‐D‐xylo‐hex‐5‐enofuranose (6) is formed in the reaction of 4a(‐R = R′ = Me) with CF3CO2H, ClC(O)Z (Z = Ph, Me or OEt), SO2 or (NC)2CC(CN)2Phenyl‐tin bond cleavage is the predominant, if not sole, reaction of 4b (R = R′ = Ph) with CF3CO2H or I2.
Preparation and structure of triorganotin, triorganolead and tetraphenylantimony derivatives of acetylenedicarboxylic acid, terephthalic acid and dithioterephthalic acid
Authors: Glowacki A. , Huber F. , Preut H. 
Published: September 2010

AbstractTriorganotin, triorganolead and tetraphenylantimony derivatives of acetylenedicarboxylic acid (H2ADC), terephthalic acid (H2TER) and dithioterephthalic acid (H2DTT) (R3M)2X (M = Sn, Pb; R = Me, Ph; X = ADC, TER, DTT) and (Ph4Sb)2X (X = ADC, TER) were prepared by neutralization of R3MOH or Ph4SbOH with the appropriate acid (X = ADC, DTT) or by reaction of R3MCl or Ph4SbCl with K2TER. The crystal structures of (Me3Sn)2ADC and (Me3Sn)2TER were determined by X‐ray diffraction. The Sn atoms are in slightly distorted trigonal‐bipyramidal environments, with C(Me) in the equatorial plane and O(carboxyl) in apical positions. The carboxylate groups are bridging, leading to the formation of a two‐dimensional polymer of puckered 22‐membered [(Me3Sn)2ADC] and 26‐membered [(Me3Sn)2TER] rings. From vibrational spectra, analogous structures are inferred for solid (Ph3Sn)2ADC, (R3Pb)2ADC (R = Me, Ph), and (Me3Pb)2TER, but structures with unidentate ‐ COO and ‐ COS groups and tetracoordinated Sn or Pb and pentacoordinated Sb are proposed for the other compounds. The DTT ligands are linked by S bonds to M. According to IR and 1H NMR studies the polymeric species dissociate on dissolution so that generally species with unidentate carboxylate groups are present. Sn and Pb in (R3M)2X (X = ADC, TER) are apparently tetracoordinated in CHCl3, but pentacoordinated in DMSO by addition of a solvent molecule.
Characterization of uranyl soaps by spectroscopic and thermal measurements
Authors: Mehrotra K. N. , Sharma Meera , Gahlaut A. S. 
Published: September 2010

AbstractThe infrared and visible spectrophotometric data of uranyl soaps showed that metaloxygen bonds in uranyl soaps are not purely ionic but are partially covalent in character. The X‐ray diffraction patterns confirmed the double‐layer structure with molecular axes perpendicular to the basal plane. The thermal decomposition of these soaps was found to be kinetically of zero order and the energies of activation were found to lie between 14‐58 kJ/mol.
Sulfonation and sulfation on reaction of 1,2‐dihydroxybenzene and its methyl ethers in concentrated aqueous sulfuric acid
Authors: Cerfontain Hans , Coenjaarts Norbert J. , Koeberg‐Telder Ankie 
Published: September 2010

AbstractThe homogeneous sulfonation of 1,2‐dihydroxybenzene (1), its monomethyl (2) and dimethyl ether (3) in concentrated aqueous sulfuric acid at 25°C has been studied and isomer distributions, as well as rate coefficients for the sulfonation of 1–3 and their monosulfonic acids, have been determined. In 73.5‐87.5% H2SO4, 1 yields the 3‐ and 4‐sulfonic acids in a ratio of 25:75, 2 yields the 4‐, 5‐ and 6‐sulfonic acids in a ratio of 46:36:18 in 73.5% H2SO4 and 50:39:11 in 87.5% H2SO4, whereas 3 yields only the 4‐sulfonic acid. The remarkable absence of the 3‐sulfonic acid (< 2%) with the 2‐methoxy substrates 2 and 3 is discussed in terms of conformer populations of the reactants. In sulfuric acid > 87.5% H2SO4, the 4‐sulfonic acid of 1 and the 5‐sulfonic acid of 2 are present in part in the form of their hydrogen sulfate. In that acid region, the 3‐ and 4‐sulforic acids of 1 both yield the 3,5‐disulfonic acid, the 4‐ and 6‐sulfonic acids of 2 both yield the 4,6‐disulfonic acid and the 4‐sulfonic acid of 3 mainly yields the 4,6‐ together with some 4,5‐disulfonic acid.
A partial synthesis of 13‐ethyl‐11‐methylene‐18,19‐dinor‐17α‐pregn‐4‐en‐20‐yn‐17‐ol (desogestrel) based upon intramolecular oxidation of an 11β‐hydroxy‐19‐norsteroid to the 18 → 11β‐lactone
Authors: van den Heuvel M. J. , van Bokhoven C. W. , de Jongh H. P. , Zeelen F. J. 
Published: September 2010

AbstractA partial synthesis of the 13‐ethyl‐18‐norsteroid desogestrel is reported. The key step in this synthesis is the intramolecular oxidation of 11β‐hydroxyestr‐5‐ene‐3,17‐dione cyclic bis‐(1,2‐ethanediyl acetal) 3 with Pb(OAc)4 and iodine to 3,3:17,17‐bis[1,2‐ethanediylbis(oxy)]‐11β‐hydroxyestr‐5‐en‐18‐oic acid γ‐lactone 2.The 13‐COOH group was then converted into a 13‐ethyl group by a Grignard reaction with methyl‐magnesium bromide followed by Wolff‐Kishner reduction of the 13‐acetyl group thus formed.
Synthesis of vinca alkaloids and related compounds XXXVIII: Formation of dimers under Polonovski reaction conditions
Authors: Moldvai István , Kálmán Alajos , Szántay Csaba , Tóth Gábor , Vedres András 
Published: September 2010

AbstractThe dimeric products (la‐c) have been prepared by treatment of N‐oxides derived from some indole alkaloids. Their structures have been elucidated by detailed NMR investigations and the structure of 1c determined by X‐ray analysis. The importance of the E2‐type trans‐axial elimination of the N‐acyloxy intermediate in the dimer formation has also been established. The iminium salts 4a‐b and the derived pseudocyanide 6 have been prepared.
Enzymes that do not work in organic solvents: Too polar substrates give too tight enzyme‐product complexes
Authors: Kieboom Antonius P. G. 
Published: September 2010

AbstractThe possible effect of hydration of both the enzyme active site and the substrate or product on enzyme complex formation has been evaluated.Replacement of water by organic solvents in the case of highly polar substrates, e.g. carbohydrates, phosphates, sulfates, leads to such an enhancement of enzyme‐substrate and/or enzyme‐product complex stability that there is no measurable conversion. The very low rate of dissociation of the enzyme‐product complex simply prevents these polar‐substrate converting enzymes to be catalytically effective in apolar media. Proper less‐polar substrates, on the other hand, might be more promising.
Syntheses of some N‐(pyrazinecarbonyl) amino acids and peptides
Authors: Kočvar Marijan , Polanc Slovenko , Verček Bojan , Tišler Miha 
Published: September 2010

AbstractDerivatives of some amino acids, having a pyrazinecarbonyl or 3‐aminopyrazinecarbonyl radical, have been synthesized and some peptides prepared. In the case of the 3‐aminopyrazinecarbonyl derivatives, condensed pyrimidines, i.e. 4(3H)‐pteridinone derivatives, could be prepared.
Oxidation of 1‐hydroxyazetidines to four‐membered cyclic nitrones and β‐lactams
Authors: van Elburg P. A. , Reinhoudt D. N. 
Published: September 2010

AbstractThe 1‐(benzyloxy)azetidines 7a‐c and 16a,b were synthesized by reductive cyclization of the corresponding oximes 5a‐c and 14a‐d. Oxidation of the 1‐hydroxyazetidines 8a‐c and 17 with PbO2 afforded the corresponding four‐membered cyclic nitrones 18a‐c and the bicyclic four‐membered nitrones 18d and 18e, which were characterized as the cycloadducts 19a‐c and 20 by reaction with dimethyl acetylenedicarboxylate. Pb(OAc)4 oxidation of the monocyclic l‐hydroxy‐azetidine 8a gave 1,4‐bis(acetyloxy) β‐lactam 22a and 1,4,4‐tris(acetyloxy) β‐lactam 23a, while oxidation of the 1‐hydroxyazetidines 8b,c gave exclusively the 1,4‐bis(acetyloxy) β‐lactams 22b and 22c. Oxidation of bicyclic l‐hydroxyazetidine 17 with Pb(OAc)4 afforded the bicyclic bis(acetyloxy) β‐lactam 21.
Photochemical isomerizations of 2‐vinyl‐2‐phenylcyclohexanone; ketene, alkenal and 1,3‐acyl shift product formation from the excited singlet state
Authors: Koppes Margareth J. C. M. , Cerfontain Hans 
Published: September 2010

AbstractThe photochemistry of 2‐vinyl‐2‐phenylcyclopentanone (1) and 2‐vinyl‐2‐phenylcyclohexanone (2) has been studied under conditions of both direct (λ 300 nm) and triplet‐sensitized irradiation. Whereas compound 1 is photostable, compound 2 yields three photochemical isomerization products upon direct irradiation, viz. the ring‐expanded phenylcyclooctenone 8 (ϕ = 0.43), (E)‐and (Z)‐phenyloctadienals 9 (ϕ = 0.06 for each geometric isomer) and a ketene, which, in 2‐propanol, affords the corresponding ester 10 (ϕ = 0.08). In these rearrangements, the intermediacy of a common singlet diradical, formed by initial α‐cleavage, is suggested. This diradical yields the alkenals and ketene by intramolecular 1,5‐H shifts and cyclizes to the 1,3‐AS 8 and the starting material.
Sulfonation of chloro‐ and dichloroanisoles with concentrated aqueous sulfuric acid and sulfur trioxide. Demethylation of chloroanisolesulfonic acids in sulfuric acid systems
Authors: de Wit Peter , Cerfontain Hans 
Published: September 2010

AbstractThe nine chloro‐ and dichloroanisoles have been sulfonated with sulfuric acid. The observed sulfonic acid isomer distributions are determined mainly by the ortho‐ and para‐ directing effect of the methoxy substituent. In the reaction with sulfuric acid, the initially formed chloro‐ and dichloroanisolesulfonic acids are demethylated to give the corresponding phenolsulfonic acids. Demethylation occurs only in those cases where the methoxy substituent is sterically hindered by an o‐chloro and/or o‐sulfo substituent. Reaction of 2,3‐ and 3,5‐dichloroanisole with fuming sulfuric acid yields initially the 4,6‐ and 2,4‐disulfonic acids, respectively. The disulfonic acids are converted to the corresponding hydrogen sulfates either by direct sulfodemethylation or by protodemethylation followed by subsequent sulfation. The 2,3‐dichloro‐4,6‐disulfophenyl hydrogen sulfate cyclizes to the 1,3,2,4‐benzodioxadithiin 2,2,4,4‐tetraoxide 4.The sulfonation of the chloro‐ and dichloroanisoles with SO3 in the solvents nitromethane or CCl3F leads only to sulfodeprotonation.