Pyrazoles, methyl-substituted

For fV-methylpyrazoIe (99), the molecular ion of which is less intense than pyrazole (a common feature for methyl-substituted pyrazoles (67ZOR1540)), the fragmentation pattern involves the methyl group (Scheme 2). These results were established using H, C and N labelling studies. 

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. 

Although the electrocyclic ring closure-heteroatom migration pathway adequately rationalizes the formation of the Pg and P7 imidazoles, until recently the P4 pathway has been less well understood. As in the case of 1,4-dimethyl-pyrazole 15, 1-phenylpyrazole 29 and the methyl substituted-1-phenylpyrazoles... 

Me3ln reacts with various methyl-substituted pyrroles to give dimers [Me2lnNC4R4] (R = H, Me) in which the bridging atom is an sp carbon of the heterocycle (In-C 257.5pm), similar to the n-dimers M62M (C4H3NMe)-2 (Section 2.1). (Cycio-C5H9) 2ln (pyrazole) is also claimed to be a dimer from mass spectral evidence. 

Simple HMO calculations (68JCS(B)725) satisfactorily account for the UV spectra of a great number of pyrazoles substituted by methyl and phenyl groups. The spectra of pyrazolium and indazolium salts (free bases in IN HCl) have been compared with calculated transitions (Pariser-Parr-Pople method) (74MI40403). 

The basicities of indazole (1.31), 1-methyl (0.42) and 2-methyl (2.02) derivatives and of eight other substituted indazoles have been measured (67BSF261 The effect of substituents in the 3-position is similar in pyrazoles and indazoles with Api values as follows Me, 0.80 and 0.86 Cl, -3.01 and -2.98 Br, -2.85 and -2.82, respectively. A nitro group in the homocycle has an expected base-weakening effect of -2 pK units, whether it is at the 5- or the 6-position. 

Diethyl 0-(3-methyl-5-pyrazolyl) phosphate (722) and 0,0-diethyl 0-(3-methyl-5-pyrazolyl) phosphorothioate (723) were prepared in 1956 by Geigy and they act, as do all organophosphates in both insects and mammals, by irreversible inhibition of acetylcholinesterase in the cholinergic synapses. Interaction of acetylcholine with the postsyn-aptic receptor is therefore greatly potentiated. 0-Ethyl-5-n-propyl-0-(l-substituted pyrazol-4-yl)(thiono)thiolphosphoric acid esters have been patented as pesticides (82USP4315008). 

Thieno[3,4-d]oxazole-3a(4H)-carboxylic acid, dihydro-2-methyl-synthesis, 6, 1020 Thieno[2,3-d Joxazoles synthesis, 6, 990 Thieno[3,2-g]pteridine structure, 3, 284 lH-Thieno[3,4-c]pyran-2-ones synthesis, 4, 1032 Thienopyrazines synthesis, 4, 1022-1024 Thieno[2,3-6]pyrazines, 4, 1023 electrophilic substitution, 4, 1024 Thieno[3,4-6]pyrazines, 4, 1024 Thieno[3,4-c]pyrazole, 4,6-dihydro-3-hydroxy-carbamates... 

X-Ray crystal structure determinations of l-(aminocarbonyl)-3-methyl-4-methoxy-l//-pyrazol-5(2H)-one 107 (R = H) and l-(phenylaminocar-bonyl)-3-methyl-4-methoxy-l//-pyrazol-5(2H)-one 107 (R = Ph) demonstrated that both molecules exist in the crystal exclusively as NH-CO tautomers (97T5617). The tautomeric form similar to 104b is realized in the crystal of 4,4-dichloro-substituted pyrazolone 108 (93BSB735). 

Abbreviations acac, acetylacetonate Aik, alkyl AN, acetonitrile bpy, 2,2 -bipyridine Bu, butyl cod, 1,5- or 1,4-cyclooctadiene coe, cyclooctene cot, cyclooctatetraene Cp, cyclopentadienyl Cp, pentamethylcyclopenladienyl Cy, cyclohexyl dme, 1,2-dimethoxyethane dpe, bis(diphenyl-phosphino)ethane dppen, cis-l,2-bis(di[Atenylphosphino)ethylene dppm, bis(diphenylphosphino) methane dppp, l,3-bis(diphenylphosphino)propane eda,ethylenediamine Et,ethyl Hal,halide Hpz, pyrazole HPz, variously substituted pyrazoles Hpz, 3,5-dimethylpyrazole Me, methyl Mes, mesityl nbd, notboma-2,5-diene OBor, (lS)-endo-(-)-bomoxy Ph, phenyl phen, LlO-phenanthroline Pr, f opyl py, pyridine pz, pyrazolate Pz, variously substituted pyrazolates pz, 3,5-dimethylpyrazolate solv, solvent tfb, tetrafluorobenzo(5,6]bicyclo(2.2.2]octa-2,5,7-triene (tetrafluorobenzobanelene) THE, tetrahydrofuran tht, tetrahydrothicphene Tol, tolyl. 

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