Bis[(2,2-dimethyl­propano­yloxy)meth­yl] {[2-(6-amino-9H-purin-9-yl)eth­oxy]meth­yl}phospho­nate–succinic acid (2/1)

The title compound, C20H32N5O8P·0.5C4H6O4, is composed of two 9-{2-[bis­(pivaloyloxymeth­oxy)phosphinylmeth­oxy]eth­yl}adenine, commonly known as adefovir dipivoxil (AD), mol­ecules linked to the carb­oxy­lic acid groups of succinic acid (SA). The asymmetric unit contains one mol­ecule of AD and half a mol­ecule of SA, which sits on an inversion center. Both adenine units in the two AD mol­ecules make AD–SA N—H⋯O and SA–AD O—H⋯N hydrogen bonds to SA. In addition, the inter­molecular AD–AD N—H⋯O—P hydrogen bond serves to stabilize the cocrystal. There is also a π–π stacking inter­action [inter­planar spacing 3.34 (19) Å] between adjacent inversion-related adenine groups

Liquid-Assisted Grinding to Prepare a Cocrystal of Adefovir Dipivoxil Thermodynamically Less Stable than Its Neat Phase

Liquid-assisted grinding was employed to generate a cocrystal of adefovir dipivoxil (AD) and glutaric acid (GLU), which had not been successfully obtained through solution crystallization. The cocrystal formation was confirmed with powder X-ray diffraction, and its thermal stability and release behavior were studied through differential scanning calorimetry and dissolution experiments, respectively. The AD/GLU cocrystal was less stable than neat AD phase and the previously reported AD cocrystals with other dicarboxylic acids, such as suberic acid and succinic acid. This suggests that the intermolecular interactions of the AD/GLU cocrystal are probably weaker than the other crystal phases. The release behavior of the AD/GLU was comparable with the cocrystal with suberic acid. The current study verifies the effectiveness of the liquid-assisted grinding for the preparation of the thermodynamically less stable cocrystal phase

Phase Transformation of Adefovir Dipivoxil/Succinic Acid Cocrystals Regulated by Polymeric Additives

The polymorphic phase transformation in the cocrystallization of adefovir dipivoxil (AD) and succinic acid (SUC) was investigated. Inspired by biological and biomimetic crystallization, polymeric additives were utilized to control the phase transformation. With addition of poly(acrylic acid), the metastable phase newly identified through the analysis of X-ray diffraction was clearly isolated from the previously reported stable form. Without additives, mixed phases were obtained even at the early stage of cocrystallization. Also, infrared spectroscopy analysis verified the alteration of the hydrogen bonding that was mainly responsible for the cocrystal formation between AD and SUC. The hydrogen bonding in the metastable phase was relatively stronger than that in the stable form, which indicated the locally strong AD/SUC coupling in the initial stage of cocrystallization followed by the overall stabilization during the phase transformation. The stronger hydrogen bonding could be responsible for the faster nucleation of the initially observed metastable phase. The present study demonstrated that the polymeric additives could function as effective regulators for the polymorph-selective cocrystallization

Electrocatalytic Hydrogenation and Hydrogenolysis of Furfural and the Impact of Homogeneous Side Reactions of Furanic Compounds in Acidic Electrolytes

The electrochemical hydrogenation and hydrogenolysis (ECH) of furfural (FF) on a copper electrocatalyst has been investigated to produce biofuels and fine chemicals in an H-type batch reactor at room temperature. We report a systematic study of ECH of FF to gain a better understanding of the relationships between products and reaction conditions: current density, electrolyte, and cosolvent ratio in acidic solutions. The acidity of electrolytes had the most significant impact on the product distribution. Mildly acidic electrolytes mainly produced furfuryl alcohol (FA), while strongly acidic electrolytes produced both 2-methyl furan (MF) and FA. Also, the yield of products depended on the current density and reaction time when equivalent charge was transferred to the reaction. However, the mole balance accounting for FF, MF, and FA was not higher than 70% in any reaction condition when the theoretical amount of electrons for complete MF production from FF (e^–/FF = 4) was transferred to the system. The investigation of nonelectrochemical homogeneous side reactions suggested that the low mole balance in a mildly acidic electrolyte may be from the charge transfer promoted side reactions on the copper electrode. On the other hand, it was shown that the low mole balance in strongly acidic electrolytes was due to homogeneous side reactions

Carbon dioxide-cofeeding pyrolysis of pine sawdust over nickle-based catalyst for hydrogen production

This study aimed to determine the synergistic effects of CO2 on the catalytic pyrolysis of pine sawdust over a Ni-based catalyst (Ni/SiO2) to establish a sustainable platform for H2 production. To elucidate the reaction mechanism, the CO2-cofeeding pyrolysis of pine sawdust was performed. The CO2-cofeeding pyrolysis of pine sawdust proved that the gas-phase reaction between CO2 and pyrolysates led to the increase in the amount of generated CO. The CO2 enhanced thermal cracking and dehydrogenation. These mechanistic features of CO2 were catalytically enhanced when Ni/SiO2 was employed as heterogeneous catalyst, which led to an increase in the amounts of generated H2 and CO. Hence, the CO that was additionally generated during the gas-phase reaction of CO2 and pyrolysates could be further converted into H2. In addition, CO2 could be looped in the CO2-cofeeding pyrolysis of pine sawdust. Furthermore, exploiting CO2 as raw material or reactive gas medium in the catalytic pyrolysis process also offered a strategic means for preventing coke formation