Ozonolysis of Bicyclic 1,2-Dioxines: Initial Scope and Mechanistic Insights

The ozonolysis of bicyclic 1,2-dioxines was investigated using a variety of 1,4-disubstituted 1,2-dioxines along with a 1,3-dialkyl and steroidal example, with yields ranging from moderate to excellent. Two different pathways were observed upon reaction of the 1,4-disubstituted 1,2-dioxines with ozone; one pathway saw the “expected” results, that is, cleavage of the olefinic moiety with generation of 1,4-dicarbonyl 1,2-dioxines, while the other pathway revealed a previously unobserved rearrangement involving cleavage of the peroxide linkage along with loss of either CO or CO₂. Several unsymmetrical ozonolyses were also performed to further investigate the origins of this rearrangement, and initial mechanistic insights into the fragmentation pathways are discussed

Ozonolysis of Bicyclic 1,2-Dioxines: Initial Scope and Mechanistic Insights

The ozonolysis of bicyclic 1,2-dioxines was investigated using a variety of 1,4-disubstituted 1,2-dioxines along with a 1,3-dialkyl and steroidal example, with yields ranging from moderate to excellent. Two different pathways were observed upon reaction of the 1,4-disubstituted 1,2-dioxines with ozone; one pathway saw the “expected” results, that is, cleavage of the olefinic moiety with generation of 1,4-dicarbonyl 1,2-dioxines, while the other pathway revealed a previously unobserved rearrangement involving cleavage of the peroxide linkage along with loss of either CO or CO₂. Several unsymmetrical ozonolyses were also performed to further investigate the origins of this rearrangement, and initial mechanistic insights into the fragmentation pathways are discussed

Synthesis of Guaia-4(5)-en-11-ol, Guaia-5(6)-en-11-ol, Aciphyllene, 1-<i>epi</i>-Melicodenones C and E, and Other Guaiane-Type Sesquiterpenoids via the Diastereoselective Epoxidation of Guaiol

The diastereomeric ratio of epoxidation of the internally bridged carbon–carbon double bond of guaiol (<b>1a</b>) is strongly influenced by the combined effects of the types of remote protecting groups on the hydroxyisopropyl side chain, choice of solvent, and epoxidizing reagent. This observation has allowed us to devise concise stereoselective syntheses of a range of guaiane-type sesquiterpenoids via an epoxidation, ring-opening/elimination, and functionality manipulation sequence. Natural products guaia-4(5)-en-11-ol (<b>2a</b>), guaia-5­(6)-en-11-ol (<b>3</b>), and aciphyllene (<b>4a</b>) and epimers of the recently isolated natural products, 1-<i>epi</i>-guaia-4­(5)-en-11-ol (<b>2b</b>), 1-<i>epi</i>-aciphyllene (<b>4b</b>), and 1-<i>epi</i>-melicodenones C (<b>5a</b>) and E (<b>6a</b>), were synthesized in good yields in relatively few steps

Molecular Structures of Isomeric Ortho, Meta, and Para Bromo-Substituted α‑Methylsulfonyl-α-diethoxyphosphoryl Acetophenones by X‑ray and DFT Molecular Orbital Calculations

The X-ray single crystal analysis of isomeric ortho, meta, and para bromo-substituted α-methylsulfonyl-α-diethoxyphosphoryl acetophenones showed that this class of compound adopts synclinal (gauche) conformations for both [-P­(O)­(OEt)₂] and [-S­(O)₂Me] groups, with respect to the carbonyl functional group. The phosphonate, sulfonyl, and carbonyl functional groups are joined through an intramolecular network of attractive interactions, as detected by molecular orbital calculations at the M06-2X/6-31G­(d,p) level. These interactions are responsible for the more stable conformations in the gas phase, which also persist in the solid-state structures. The main structural distinction in the title compounds relates to the torsion angle of the aryl group (with respect to the carbonyl group), which gives rise to different interactions in the crystal packing, due to the different positions of the Br atom

Perovskite-Structured PbTiO₃ Thin Films Grown from a Single-Source Precursor

Perovskite-structured lead titanate thin films have been grown on FTO-coated glass substrates from a single-source heterometallic molecular complex, [PbTi­(μ₂-O₂CCF₃)₄(THF)₃(μ₃-O)]₂ (<b>1</b>), which was isolated in quantitative yield from the reaction of tetraacetatolead­(IV), tetrabutoxytitanium­(IV), and trifluoroacetic acid from a tetrahydrofuran solution. Complex <b>1</b> has been characterized by physicochemical methods such as melting point, microanalysis, FTIR, ¹H and ¹⁹F NMR, thermal analysis, and single-crystal X-ray diffraction (XRD) analysis. Thin films of lead titanate having spherical particles of various sizes have been grown from <b>1</b> by aerosol-assisted chemical vapor deposition at 550 °C. The thin films have been characterized by powder XRD, scanning electron microscopy, and energy-dispersive X-ray analysis. An optical band gap of 3.69 eV has been estimated by UV–visible spectrophotometry

Perovskite-Structured PbTiO₃ Thin Films Grown from a Single-Source Precursor

Perovskite-structured lead titanate thin films have been grown on FTO-coated glass substrates from a single-source heterometallic molecular complex, [PbTi­(μ₂-O₂CCF₃)₄(THF)₃(μ₃-O)]₂ (<b>1</b>), which was isolated in quantitative yield from the reaction of tetraacetatolead­(IV), tetrabutoxytitanium­(IV), and trifluoroacetic acid from a tetrahydrofuran solution. Complex <b>1</b> has been characterized by physicochemical methods such as melting point, microanalysis, FTIR, ¹H and ¹⁹F NMR, thermal analysis, and single-crystal X-ray diffraction (XRD) analysis. Thin films of lead titanate having spherical particles of various sizes have been grown from <b>1</b> by aerosol-assisted chemical vapor deposition at 550 °C. The thin films have been characterized by powder XRD, scanning electron microscopy, and energy-dispersive X-ray analysis. An optical band gap of 3.69 eV has been estimated by UV–visible spectrophotometry

Postsynthetic Metathesis in an All Organic Two-Dimensional Array Mediated by Hydrogen Bonding

Cocrystallization of equimolar quantities of sulfathiazole (STL) with each of 1,4-diazabicyclo­[2.2.2]­octane (DABCO) and piperazine (PIP) resulted in facile formation of salts [DABCOH]­[STL_H] (<b>1</b>) and [PIPH]­[STL_H] (<b>2</b>), respectively. Crystallography shows the formation of aniline-N–H···O­(sulfonyl) hydrogen bonds between anions to form supramolecular undulating and zigzag layers, respectively, with the cations being connected to these by charge-assisted N–H···N­(thioazole) interactions. ¹H NMR, IR, and Raman spectroscopies as well as powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) confirmed salt formation. Solid state grinding competition experiments were monitored by PXRD. In a sequence of experiments where STL was coground with a molar equivalent of PIP and <i>n</i> equivalents of DABCO (with <i>n</i> increasing from 0.1 to 1.0 in 0.1 increments), preferential formation of <b>1</b> was observed. In related experiments where <b>2</b> was ground with an equimolar amount of DABCO, substitution of PIPH⁺ by DABCOH⁺ was evident; i.e., postsynthetic metathesis had occurred to about 70% for dry grinding. Quantitative yields were obtained in the case of liquid-assisted grinding (LAG) with a few drops of ethanol after 1.4 equiv of DABCO were added. These observations are primarily correlated with differences in aniline-N–H···O­(sulfonyl) hydrogen bonding that sustain the layers