ChemInform Abstract: Intermolecular Triple Proton and Deuteron Transfer in Crystalline 3,5‐Dimethylpyrazole Studied by NMR, NQR, and X‐Ray Methods

Abstract

ChemInform Abstract (space group: R3c; formation of discrete hydrogen-bonded cyclic trimers, in which the H-atoms move in a symmetrical, double minimum energy surface; dynamics of the annular prototropic tautomerism).

Directed Synthesis of a 1D Double‐Chain Polyoxometalate Assembly: {[Ag2(bppy)3][Ag(bppy)2][Ag(bppy)]2PW11Co(bppy)O39}·2H2O

“…However, ligand packing effects are not responsible for the pairing as is demonstrated by the crystal structure of [3,5-Me 2 pzH] 3 which exhibits a planar trimeric association rather than a dimeric ''packing''. [43] On the contrary, ligand repulsion may actually prevent the silver atoms from fully eclipsing to give AgϪAg contacts. [44] The interesting aspect of this structure is the multiple role of the conjugated organic bppy: its first function is to act as a pendant ligand to functionalise the polyanions.…”

The Molecular and Crystal Structure of 3,5-Dimethylpyrazole with Chloranilic Acid Adduct

“…3 The geometry of the 3,5DMP ring shows a similar pattern of bond distances and angles as pyrazole, 4 and shows an insignificant effect of the hydrogen-bonding interaction on the bonded X-ray Structure Analysis Online carbon atoms. The C-CH3 bond distances; 1.489(2)Å and 1.492(2)ÅfallwithintheapproximateC-CH3bondlengthvalue (1.50 Å), 5 and suggest that the methyl groups attached to the carbon atoms in the pyrazole ring could not be involved in an out-of-plane motion, and may be the reason for the corresponding torsional angles (C8-C9-C10-C11; 178.1(15), C10-C9-C8-C7; 179.9(15)˚). The positions of the methyl groups in the pyrazole ring play significant role in the H-bond network, but have an insignificant effect on the bond lengths, angles and torsional angles, nor pack in a manner with any stericeffects.Theadductdoesnotexhibitanydimeric,trimeric, nortetramericarrangement,asalsoobservedina1:2complexes ofCLAwithpyrazoleandimidazole, 6 and4-methylimidazole.…”

Highly regioselective synthesis of novel 1,4'-bipyrazoles

“…When the b-dimethylaminoenones 3a-b reacted with hydrazine monohydrate in ethanol at room temperature for 5 h, the corresponding 1,4'-bipyrazoles 4a (in 71% yield) and 4b (in 80% yield) were obtained; and when reacted with tert-butylhydrazine hydrochloride or phenylhydrazine hydrochloride in ethanol at 60 °C for 5 h, 1,4'-bipyrazoles 5a-b and 6a-b were obtained, respectively. After an initial screen of solvents and reaction temperatures, the 1,4'-bipyrazole 7a was synthesized by the cyclocondensation reaction of the b-dimethylaminoenone 3a with carboxymethylhydrazine and the use of one equivalent of BF 3 • OEt 2 in anhydrous MeOH under reflux for 10 h in 72% yield. On the other hand, the reaction of the b-dimethylaminoenone 3b with carboxymethylhydrazine using these conditions did not give the expected 1,4'-bipyrazole 7b.…”

“…A mixture of b-dimethylaminoenone 3a (1 mmol), carboxymethylhydrazine (1.2 mmol) and BF 3 . OEt 2 (1.2 mmol) was stirred at reflux temperature of methanol (1 mL) for 10 h. Then the mixture was extracted with dichloromethane (3 mL) and washed with water (3 × mL).…”

“…Currently, there is a particular interest in bipyrazoles substituted in studies on intermolecular interactions with the participation of pyrazoles and their derivatives. [3][4][5][6][7][8][9] The structure of pyrazole molecules, containing the fragment RN-N(H)-, is favorable in the formation of various hydrogen bonded complexes and associates in solid-cyclic dimers, trimers and tetramers, linear chains and helices, depending on the substituent. [9][10][11] A literature survey turned up a few reports on 1,4'-bipyrazole and isoxazole synthesis and structure.…”