Imides of 2-Trifluoroacetylphenol and other Trifluoracetic acid Esters: Novel Reactions with Phosphorus(III) Derivates

Abstract

The imido derivates of 2-trifluoroacetylphenol, 1 (R¹=H, Me, iPr) react with the isocyanatophosphites (R²O)₂PNCO, 2 (R²[dbnd]Et, R²-R²[dbnd]CMe₂-CMe₂) to yield the bicyclic compounds 3, wheras in case of 1 (R¹[dbnd](CH₂)₂NMe2) the λ³σ³P compounds 4 are found. The phosphorus(III) chlorides R3PC12 (R³[dbnd]Ph, OEt) and 1 (R¹[dbnd]H, Me) give rise to furnish the tricyclic phosphoranes 5. However with 1 (R¹[dbnd]iPr) phosphite 6 is obtained, which adds hexafluoracetone to give the 1,3,2λ⁵σ⁵-dioxaphospholane 7. 2-(Trifluoracetoxy)pyridine 8. reacts with Tris(trimethylsily1)phosphite to yield the bis(phosph0nate) 10. Some molecular structures are discussed on the basis of x-ray diffraction results.     

1,1,1,4,5,5,5-Heptafluoro-4-(trifluoromethyl)-2,3-pentanedione,a potent reagent for the synthesis of cyclic λ5σ5 phosphoranes

1,1,1,4,5,5,5-Heptafluoro-4-(trifluoromethyl)-2,3-pentanedione reacted with λ³σ³-phosphorus compounds, PR¹R²R³ (R¹ = CF₃, R² = R³ = Me, iPr, NEt₂; R¹ = NCO, R² = R³ = OMe, OEt, R²−R³ = OCH₂CH₂O, OCMe₂CMe₂O; R¹ = OSiMe₃, R² = R³ = OEt; R¹ = NEt₂, R² = R³ = OCH₂CF₃; R¹ = R² = Et₂N, R³ = OCH₂CF₃, OCH(CF₃)₂, OCH₂Ph, OC₆F₅) to give new 1,3,2λ⁵σ⁵-dioxaphospholenes. The first λ⁵σ⁵ phosphoranes with an OCN group bonded to phosphorus were obtained. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:109–113, 1998     

Line narrowing of excited-state transitions in nonlinear polarization spectroscopy: application to water-soluble chlorophyll-binding protein

The homogeneous linewidth of dye aggregates like photosynthetic light-harvesting complexes contains important information about energy transfer and relaxation times that is, however, masked by inhomogeneous broadening caused by static disorder. Whereas there exist line narrowing techniques for the study of low-energy exciton states, the homogeneous linewidth of the high-energy states is not so easy to decipher. Here we present a microscopic theory for nonlinear polarization spectroscopy in the frequency domain that contains a dynamic aggregate selection revealing the homogeneous linewidth of these states. The theory is applied to the water-soluble chlorophyll-binding protein for which the high-energy exciton state was predicted to exhibit a sub-100-fs lifetime.     

Structure control in PMMA/silica hybrid nanoparticles by surface functionalization

Hydrophilic silica particles need to be hydrophobized to be encapsulated in a polymeric environment, which can be achieved by different methods. We report on the relationship between different hydrophobization techniques of silica and the final structure of poly(methyl methacrylate)/silica hybrid nanoparticles obtained by miniemulsion polymerization. Hydrophobization by cetyltrimethylammonium chloride (CTMA-Cl) uses the ionic interaction between the positively charged ammonium salt and the negatively charged silica surface, as shown by isothermal titration calorimetry. In this case, the interaction between polymer and silica surface needs to be enhanced, so 4-vinylpyridine (4-VP) was used as a co-monomer. Alternatively, the condensation reactions of 3-methacryloxypropyltrimethoxysilane (MPS) and octadecyltrimethoxysilane (ODTMS) were used to provide a covalent bond to the silica surface. The condensation reaction of the trimethoxysilane groups onto the silica surface was proven by Fourier transform infrared spectroscopy and thermogravimetric analysis. Hybrid nanoparticles were successfully formed with silica particles functionalized with the different functionalization agents. However, the structure of the resulting hybrid particles (i.e., the distribution of the silica particles within the polymer matrix) depends on the agent. The MPS-functionalized silica particles copolymerize with poly(methyl methacrylate), leading to a fixation of the silica particles inside the polymer and to a homogeneous distribution. The CTMA-Cl- and ODTMS-functionalized silica particles cannot copolymerize, but aggregate at the interface, leading to a Janus-like structure.     

Structural Report for 2,5-Bis(trifluoroacetyl)cyclohexane-1,4-dione and <Emphasis Type="Italic">o</Emphasis>,<Emphasis Type="Italic">o</Emphasis>′-bis(trifluoroacetyl)-<Emphasis Type="Italic">p</Emphasis>-cresol

Abstract  

The crystal structures of 2,5-bis(trifluoroacetyl)cyclohexane-1,4-dione (1) and o,o′-bis(trifluoroacetyl)-p-cresol (2) is reported. The first compound crystallizes in monoclinic space group P2₁/n with a = 6.5040(10), b = 10.1610(10), c = 8.2420(10) ?, β = 91.690(10)° and V = 0.54445(12) nm³. Double enolization (U-structure) with a considerable electron density delocalization in the enolone backbone was established in this case. Phenol 2 crystallizes in triclinic space group P-1 with a = 7.0690(10), b = 9.4890(10), c = 9.8190(10) ?, α = 103.720(10), β = 110.760(10), γ = 102.150(10)° and V = 0.56598(12) nm³. In contrast to CDCl₃ solution, a “bifurcate” structure of 2 with jumping OH proton is quenched: only one of both trifluoroacetyl moieties is bonded by intramolecular hydrogen bond.     

Fluorinated 1,3-diketones, 2-trifluoroacetyl phenols and their derivatives: versatile reactants in phosphorus chemistry

The role of fluorinated β-diketones, their tautomers (keto–enols) and their derivatives as reagents towards λ³P compounds is reviewed, including 2-trifluoroacetyl phenols, possessing formally a keto–enol system, and their derivatives. In an ‘insertion’ reaction phosphine and the keto–enol tautomers of 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione furnished primary (S) or (R) α-hydroxy phosphines, whose enol functions probably isomerized the corresponding keto compounds. Further addition and isomerisation furnished 1,3α,5,7β-tetrakis(trifluoromethyl)-2-phospha-6-oxa-9-oxabicyclo[3.3.1]-nonan-3β,7α-diol and 1,7-trifluoromethyl-3,5-methyl-2,4,8-trioxa-6-phophaadamantane, exclusively one diastereomer in each case. The main mechanistic feature of these reactions is a consecutive diastereoselective hemiketal cyclization. 1,1,1,5,5,5-Hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, as well as 2-trifluoroacetyl phenol and its imino derivatives reacted diastereospecifically with phosphonous acid dichlorides, RPCl₂ to give in a concerted mechanism thermally stable tricyclic λ⁵σ⁵P phosphoranes containing two five-membered rings and one six-membered ring. Surprisingly, the two CF₃ groups bonded to an sp³-hybridized carbon were in a cisoid arrangement having closest non-bonding FF distances of 301.4 or 273.5 pm. These findings reflect the ‘through space’ F---F coupling constants of the tricyclic phosphoranes (J_FF=4.0–7.0 Hz), in solution. 4,4,4-Trifluoro-3-hydroxy-1-phenyl-butan-1-one and methyl or phenyl phosphonous acid dichlorides gave similar tricyclic phosphoranes decomposing at ambient temperature to furnish 1,2λ⁵σ⁴-oxaphospholanes and (E)-1,1,1-trifluoro-4-phenyl-but-2-en-4-one. Dialkylphosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione reacted to give either the (Z)-enol phosphonates or the respective γ-ketophosphonates from which in two cases four diastereomeric 2-oxo-2,5-dialkoxy-3,5-bis(trifluoromethyl)-3-hydroxy-1,2λ⁵σ⁴-oxa-phospholanes were obtained. 2-Trifluoroacetyl cyclohexanone, 4,4,4-trifluoro-3-trimethylsiloxy-1-phenylbutan-1-one, 1-benzoyl-2-trifluormethyloxirane, 1-benzoyl-2-trifluoro-methylaziridine, 2-trifluoroacetyl-1-trimethylsiloxybenzene and (trifluoroacetyl-1-phenyl) diethyl phosphate reacted with tris(trimethylsilyl) phosphite to give functionalized α-trimethylsiloxy phosphonates, which could easily be transferred into the respective phosphonic acids. In the case of an oxirane and an aziridine ketone no ring cleavage was observed. For 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone and 1,1′-(2-trimethylsiloxy-5-methyl-m-phenylene)-bis-ethanone benzoxaphospholanes were obtained. Trialkyl phosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione furnished cyclic phosphoranes containing the 3-hydroxy-3,5-bis(trifluoromethyl)-1,2λ⁵σ⁵-oxaphospholene structural element, stable at ambient temperature only in the case of one cyclic phosphite precursor. (E)-1,1,1-Trifluoro-4-phenyl-but-2-en-4-one and trimethylphosphite reacted to form 1,2λ⁵σ⁵-oxaphosphol-4-ene as the sole product. Results similar to the reaction of 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone with diethyltrimethylsilylphosphite were obtained for trimethylphosphite and 2-trifluoroacetyl phenol where a deoxygenated phosphorane was found, easily hydrolyzed to give the respective phosphonic acid. With dialkylisocyanato phosphites and the keto components, 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, 4,4,4-trifluoro-1-phenyl-1,3-butandione, 2-trifluoroacetyl cyclohexanone, 2-trifluoroacetyl phenol and 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone reacted in a ‘double’ cycloaddition to form bicyclic phosphoranes containing the 4,8-dioxa-2-aza-1λ⁵σ⁵-phosphabicyclo[3.3.0]-oct-6-en-3-one ring system; for the imino derivatives of 2-trifluoroacetyl phenol a corresponding 8-oxa-2,4-diaza- system was generated. For (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one however, a cyclic spiroimino phosphorane was obtained which underwent a [2+2] cyclodimerization to form a diazadiphosphetidine. Dimethylpropynyl phosphonite and 1,1,1,5,5,5-hexafluoropentan-2,4-dione yielded diastereoselectively a bisphosphorane, namely 1,4-bis(trifluoromethyl)-3,6-dioxa-2,2,7,7-tetramethoxy-2,7-di(1-propynyl)-2,7-diphosphabicyclo[2.2.1] heptane. When trimethylsilanyl–phosphenimidous acid bis-trimethylsilanyl–amide, Me₃SiN=PN(SiMe₃)₂, was allowed to react with 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one, 2-trifluoroacetyl cyclopentanone, 2-trifluoroacetyl phenol and its imino derivatives, 2-imino-1,2λ⁵σ⁴-oxaphospholenes were found containing two diastereomers in each case, which added hexafluoroacetone across the P=N bond to give 1,3,2λ⁵σ⁵-oxazaphosphetanes.     

Bis(trifluoroacetyl)phenols and their derivatives in reactions with selected phosphorus(III) compounds

The reactivity of bis(trifluoroacetyl)‐phenols toward selected λ³P derivatives was examined. In the case of dialkyl(isocyanato)phosphites, only one of both present trifluoracetyl moieties of substrate was involved. After addition of the phenolic OH moiety across the intermediary formed PN bond, tri‐, tetra‐, and pentacyclic α‐(trifluoromethyl)phosphoranes were produced in a highly diastereoselective reaction. An unusual deoxygenation of the intermediary hydroxyphosphorane was observed reacting 4‐methyl‐2,6‐bis‐(trifluoroacetyl)phenol with diethyl(trimethylsilyl)‐phosphite, and the subsequent hydrolysis gave γ‐hydroxy‐α‐(trifluoromethyl)phoshonate. On the contrary, during the reaction of the O‐silylated phenol with tris(trimethylsilyl)phosphite, a bis‐phosphonate was obtained that underwent heterocyclization to phosphono phosphole system. The mechanistic aspects of the studied reactions, as well as structural features of the synthesized compounds are discussed, based on the multinuclear NMR spectroscopy and X‐ray single crystal investigation data. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:474–482, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20451     

Decay Pion Spectroscopy of Electro-Produced Hypernuclei

The investigation of light hypernuclei is quite important for understanding the basic YN interaction and the mechanism of hypernuclear structure. We started the commissioning of the decay pion spectroscopy of light hypernuclei at MAMI-C in 2011. In order to realize the K⁺ tagging efficiently, some detectors on KAOS spectrometer were upgraded or newly installed. The existing and well-studied spectrometers, SpekA, SpekC were used as pion spectrometers. The analysis is ongoing to estimate the detectors performance and develop the spectrometers for future experiments with higher beam intensity. The preliminary results of the particle identification are presented in this article.     

Mono and Bisphosphonates from Perfluoro Olefins and Polyfunctional Fluoro Ketones. Syntheses,Molecular Structure and Derivatives

Perfluoroalkenyl phosphonates were formed along with Me₃SiF using CF₃CF=CF₂, CF₃CH=CF₂, F₅SCF=CF₂ or F₅SCH=CF₂ and silylated phosphites, (R¹O)₂POSiMe₃ (R¹=Et, SiMe₃). This straightforward method could be extended to perfluorobutadienes CF₂=C(R^F)C(R^F)=CF₂ (R^F F=F, CF₃). The formation of CF₃C(=O)P(=O)(OSiMe₃)₂ and further reactions to yield bisphosphonates will be described. Acetylphosphonates, R²C(=O)P(=O)(OSiMe₃)₂ (R²=CH₃, CF₃) reacted with the ketimine, CH₃C(=NiPr)Ph to give α-hydroxy-γ-imino phosphonates. Trifluoroacetylphenol and 2,6-bis(trifluoracetyl)-4-methyl-phenol have been proven to be versatile precursors for α-and γ-hydroxy phosphonates. Intermediates in these reactions were found to be cyclic λ⁵σ⁵P species.