Pyrazole, vinylation

Pyrazole, 3,4,5-tris(trifluoromethyl)-synthesis, 5, 282 Pyrazole, vinyl-reactions, 5, 261 Pyrazole, 1-vinyl-polymerization, 1, 279... 

Pyrazolecarbinols can be dehydrated to vinylpyrazoles, (438) — (446) (72JHC1373), or transformed into chloromethyl derivatives (81T987). Compound (440 R = CH2C1) thus prepared is the starting material for the synthesis of the macrocycles (226)-(228) (Section 4.04.2.1.2(vi)). Vinyl- and ethynyl-pyrazoles have been extensively studied (B-76MI40402) and many vinylpyrazoles are polymerized by free radical initiators. 

Porphyrin, 5,10,15,20-tetraphenyl-, 4, 386 Porphyrin, vinyl-synthesis, 4, 278, 279 Porphyrin coenzymes in biochemical pathways, 1, 258-260 Porphyrinogen, mcso-tetraaryl-synthesis, 4, 230 Porphyrinogens, 4, 378, 394 pyrazoles, 5, 228 synthesis, 4, 231 Porphyrins, 4, 377-442 acetylation, 4, 395 aromatic ring current, 4, 385 basicity, 4, 400 biosynthesis, reviews, 1, 99... 

Pyrazole, N-vinyl-polymerization, 5, 269 3H-Pyrazole, 3,3,5-trimethyl-irradiation, 5, 251 Pyrazole carbaldehydes reactions, 5, 260 Pyrazole carbinols dehydration, 5, 261... 

Abbreviations aapy, 2-acetamidopyridine Aik, alkyl AN, acetoniuile Ar, aryl Bu, butyl cod, 1,5-cyclooctadiene COE, cyclooctene COT, cyclooctatetraene Cp, cyclopentadienyl Cp , penta-methylcyclopentadienyl Cy, cyclohexyl DME, 1,2-dimethoxyethane DME, dimethylformamide DMSO, dimethyl sulfoxide dmpe, dimethylphosphinoethane dppe, diphenylphosphinoethane dppm, diphenylphosphinomethane dppp, diphenylphosphinopropane Et, ethyl Ec, feirocenyl ind, inda-zolyl Me, methyl Mes, mesitylene nb, norbomene orbicyclo[2.2.1]heptene nbd, 2,5-norbomadiene OTf, uiflate Ph, phenyl PPN, bis(triphenylphosphoranylidene)ammonium Pi , propyl py, pyridine pz, pyrazolate pz, substituted pyi azolate pz , 3,5-dimethylpyrazolate quin, quinolin-8-olate solv, solvent tfb, teti afluorobenzobaiTelene THE, tetrahydrofuran THT, tetrahydrothiophene tmeda, teti amethylethylenediamine Tol, tolyl Tp, HB(C3H3N2)3 Tp , HB(3,5-Me2C3HN2)3 Tp, substituted hydrotiis(pyrazol-l-yl)borate Ts, tosyl tz, 1,2,4-triazolate Vin, vinyl. 

Photolysis of the sulphinyl-3H-pyrazole 587 in ether or methylene chloride leads to the formation of a relatively stable carbene 588 that can be identified by physical methods. When the irradiation is performed in ethyl vinyl ether or in furan, the expected cyclopropanes are formed smoothly and stereospecifically683 (equation 374). 

The same reaction, carried out with conventional heating at the same temperature, took more that 6 h to give comparable yields of the products. Dihydropyrazoles were also obtained by microwave-assisted reaction of poly-substituted vinyl ketones 122 with hydrazines, followed by reaction of the unstable pyrazole 123 with electrophiles (Scheme 43) [80]. 

There is much evidence that the mechanism" of the 1-pyrazoline reactions generally involves diradicals, though the mode of formation and detailed structure (e.g singlet vs. triplet) of these radicals may vary with the substrate and reaction conditions. The reactions of the 3 f-pyrazoles have been postulated to proceed through a diazo compound that loses N2 to give a vinylic carbene." ... 

Synthesis of isomeric chiral protected (63 )-6-amino-hexahydro-2,7-dioxopyrazolo[l,2- ]pyrazole-l-carboxylic acid 280 is shown in Scheme 36. Crude vinyl phosphonate 275, obtained by treatment of diethyl allyloxycarbonylmethyl-phosphonate with acetic anhydride and tetramethyl diaminomethane as a formaldehyde equivalent, was used in the Michael addition to chiral 4-(f-butoxycarbonylamino)pyrazolidin-3-one 272. The Michael addition is run in dichloro-methane followed by addition of f-butyl oxalyl chloride and 2 equiv of Huning s base in the same pot to provide 276 in 58% yield. The allyl ester is deprotected using palladium catalysis to give the corresponding acid 277, which is... 

H-Pyr azoles readily undergo photochemically induced elimination of nitrogen to yield the corresponding cyclopropenes, often by way of detectable vinyl diazo intermediates. l-Aryl-3-methyl-2-phenyl-l-diazobut-2-enes have, in fact, been prepared in this way from the appropriate pyrazoles.345 The vinyl diazo compounds 416, obtained by irradiation of the 3//-pyrazoles 417, were further converted to cyclopropenes 418 via vinylmethylene intermediates 419 by irradiation at 10°C.346 1-Acylcyclopropenes have been... 

Bis(pyrazolyl)borate copper complex 47 has been employed as a catalyst in the homogeneous and heterogeneous styrene epoxidation reactions <00JCS(CC)1653>. Pyrazole palladacycles 48 have proven to be stable and efficient catalysts for Heck vinylations of aryl iodides <00JCS(CC)2053>. An asymmetric borane reduction of ketones catalyzed by N-hydroxyalkyl-/-menthopyrazoles has been reported <00JHC983>. 

Fattah et al., utilized /3-keto vinyl ethers (e.g., 174) in the presence of hydrazine as precursors to pyrazoles (e.g., 175) [89]. Scheme 46 gives a general illustration of this reaction. 

Alternatively to the direct use of 1,3-dicarbonyls, pyrazol-2-ones, which constitute masked 1,3-dicarbonyls, have been involved in a microwave-assisted organocatalytic MCR with aromatic aldehydes and ethyl vinyl ether leading to 2,3-dihydropyran[2,3-c]pyrazoles (Scheme 63) [167]. 

Reaction of cyanoacetic acid with formamide in hot acetic anhydride affords a product assumed to be 164. This with triethyl orthoformate gives the vinyl ether 165. The latter reacts with hydrazines to yield 166. Heating hydrazine 166 (R = H) gives pyrazolo[3,4-d]pyrimidines 167 and 168 the hydrazine 166 (R = CHsOr Ph) gives the pyrazole 169 and then 168 on heating (71JCS(C)1610). 

Diazopropene, Diazopropylene or Vinyldiozo-tnethane, (called Diazopropen, Vinyl-diazo-methan or Dia2opropylen in Ger), CH2 CH.CH N N mw 68.08, N 41.15% not isolated in the free state, gives a wine-red eth sola isomer izes to pyrazole can be prepd by adding KOH in methanol to a sol n of ally Ini trosoure thane in eth (Refs 1, 2 4) and by the method of Adamson Kenner (Refs 1 3)... 

On standing at 25°C, the spiro-3//-pyrazole 57 is converted via an isolable 3-azopyrazole to a pyrazolotriazine.96 Pyridazines have been prepared both from a 4-vinyl-3//-pyrazole by heating in acetic acid92 and from a 3-phenacyl-3//-pyrazole in strong base.114... 

Wandelt et al. [87] have reported the application of a FILA for nucleotide monitoring. The assays were based on the fluorescence quenching of 3-diphenyl-6-vinyl-1 //-pyrazole 3.4-/ quinoline (PAQ), by guanosine 30,50-cyclic monophosphate (cGMP), adenosine 30,50-cyclic monophosphate (cAMP), and cytidine 30,50-cyclic monophosphate (cCMP). Although no analytical characterization of the polymers was reported, the authors carried out a rebinding study to ascertain the applicability of the MIPs for such application. 

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