Self-assembly of 3,5-bis(ethoxycarbonyl)pyrazolate anions and ammonium cations of beta-phenylethylamine or homoveratrylamine into hetero-double-stranded helical structures

Base mediated 1,3-dipolar cycloaddition of α-substituted vinyl phosphonates with diazo compounds for synthesis of 3-pyrazolylphosphonates and 5-pyrazolcarboxylates

5-Aryl-substituted pyrazol-3-ylphosphonates have been conveniently synthesized by 1,3-dipolar cycloaddition of 1-formamidovinylphosphonates and aryldiazomethanes under K₂CO₃/MeOH conditions at room temperature. These pyrazoles are formed in one pot via spontaneous elimination of formamide. Basic conditions prevent competitive formation of cyclopropylphosphonates. 3-Aryl substituted pyrazol-5-carboxylates can be synthesized by the same methodology from 1-arylvinylphosphonates and ethyl diazoacetate, although a stronger base NaH is necessary to ensure the success of the aromatization stage with the elimination of the diethoxylphosphoryl moiety.

A water molecule in the interior of a 1H-pyrazole Cu2+ metallocage

A pyrazole aza-macrocyclic Cu²⁺ metallocage shows the inclusion of a water molecule not hydrogen bonded with any acceptor or donor groups of the cage.

Synthesis and self-association of double-helical AADD arrays

The design and syntheses of four self-complementary oligomers that contain an underlying AADD hydrogen bond sequence are presented, and their self-association was examined in the solution and solid state. The molecular recognition between the two strands is highly sensitive to substitutions of their component heterocycles. Substitution with electron-donating and -withdrawing groups and the influence of preorganization has a large effect on the overall stabilities of the complexes studied. In particular, a wide range (>10(5) M(-1)) of stabilities with respect to substitutions at various positions in the AADD oligomers was demonstrated. In the most extreme case, the dimerization constant measured (K(dimer) ≥4.5×10(7) M(-1)) is comparable to the most stable homodimers of neutral AADD arrays reported to date.