- Thermal decomposition of triphenylphosphonium alkyl ester salts
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In thermolyses of molten triphenylphosphonium alkyl ester bromides and chlorides, alkyl = methyl, ethyl, isopropyl, at 130 and 225°C, initial attack of the halide ion on the methyl group gives the methyl halide and ylid 1, Ph3P = CH2, which can be methylated, or is protonated by the phosphonium salt with transylidation giving Ph3P+-CH3X-, X = Br, Cl. The initial reactions of the ethyl or isopropyl esters are with the halide ion, X-, as a base giving ylid, 1, which can be protonated by HX or by transylidation. The t-butyl ester generates Ph3P+-CH3X-but no products of transylidation. The first-formed ylid1, can be trapped by reactive alkyl and acyl halides, and the transient ylidic esters decompose thermally to triphenyl phosphine oxide, Ph3P = O, react further with unreacted phosphonium ester, or are trapped by added aldehyde in a Wittig reaction. The final product compositions are affected by a decrease in pressure, due to escape of volatile intermediates, and by replacement of the X- halide ion by the less nucleophilic and basic tosylate ion. Reactions under reflux, in solution in chloroform, or in suspension in benzene, are similar to those of the molten salts, but yields are generally lower at the lower temperatures. Copyright Taylor & Francis Group, LLC.
- Castaneda, Fernando,Aliaga, Christian,Acuna, Cristina,Silva, Paul,Bunton, Clifford A.
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experimental part
p. 1188 - 1208
(2009/04/16)
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- Reduction of (imine)Pt(IV) to (imine)Pt(II) complexes with carbonyl-stabilized phosphorus ylides
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A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph3P= CHCO2R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl4{NH=C(Me)-ON=CR1R2}2] [R1R2 = Me2, (CH2)4, (CH2)5, (Me)C(Me)=NOH], [PtCl4{NH=C(Me)ONR2}2] (R = Me, Et, CH2Ph), [PtCl4{N=C(Me)O-N(R3)-C(R1) (R2)}2] (R1 = H; R2 = Ph or C6H4Me; R3 = Me) as well as anionic-type platinum(IV) complexes (Ph3PCH2Ph)[PtCl5{NH=C(Me) ON=CR2}] [R2 = Me2, (CH2)4, (CH2)5] and 1 equiv of Ph3P=CHCO2R (R = Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum center. All thus prepared compounds (excluding previously described Δ4-1,2,4-oxadiazoline complexes) were characterized by elemental analyses, FAB mass spectrometry, IR and 1H, 13C{1H}, 31P(1H} and 195Pt NMR spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl2{NH=C(Me)ON=CMe2}2] [crystal system tetragonal, space group P42/n (No. 86), a = b = 10.5050(10) A, c = 15.916(3) A] and (Ph3PCH2CO2-Me)[PtCl3(NCMe)] [crystal system orthorhombic, space group Pna21 (No. 33), a = 19.661(7) A, b = 12.486(4) A, c = 10.149(3) A]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides Ph3P=CHCO2R are introduced as mild and selective reducing agents of wide applicability for the conversion of Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV) complexes for biological studies.
- Wagner,Pakhomova,Bokach,Frausto da Silva,Vicente,Pombeiro,Kukushkin
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p. 1683 - 1689
(2008/10/08)
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- FACILE SYNTHESIS OF ALKYL 5-ALKOXY-3-OXOPENTANOATES
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A facile synthesis of several alkyl 5-alkoxy-3-oxopentanoates, based on the reductive elimination of triphenylphosphine from the readily available alkyl 5-alkoxy-3-oxo-2-(triphenylphosphoranylidene) pentanoates, is described.
- Sanchez, Ignacio H.,Larraza, Maria Isabel,Brena, Francisco Kuri,Cruz, Adrian,Sotelo, Octavio,Flores, Humberto J.
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p. 299 - 308
(2007/10/02)
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- 7-Oxabicycloheptane and 7-oxabicycloheptene prostaglandin analogs
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New 7-oxabicycloheptane and 7-oxabicycloheptene prostaglandin analogs which have the general formula STR1 wherein R1 is hydrogen or lower alkyl; n is 0 to 4, m is 0 to 4 and x is 0 to 8, are useful as cardiovascular agents.
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