A Strategy for the Synthesis of 1,2-Dichlorotetrafluorocyclobutene from Hexachlorobutadiene and Its Reaction Pathway

In this paper, a novel strategy for the preparation of 1,2-dichlorotetrafluorocyclobutene (DTB) was proposed via a catalytic gas-phase process of fluorination using hexachlorobutadiene (HCBD) and anhydrous HF. In order to search for suitable catalysts and reveal the reaction pathway for this synthetic route, a series of studies were carried out. First, CrO_<i>x</i>/ZnO catalysts with different promoters (Ni, Cu, In, Al) were prepared by a precipitate method and the optimum reaction conditions were investigated. The highest activity was achieved on the Cr–Ni–Zn catalyst, whose yield of DTB reached 90% by a multiple cycle reaction. Second, the effects of different promoters on the properties of catalysts were studied by Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), temperature-programmed desorption in ammonia (NH₃-TPD), and X-ray photoelectron spectroscopy (XPS). It was found that the Cr–Ni–Zn catalyst showed the excellent catalytic performances with more CrO_<i>x</i>F_<i>y</i> species, higher oxygen concentration, and widely distributed acid strength on its surface. Third, combining experimental results with theoretical calculations, a reaction pathway has been proposed. This study offers an economic synthetic route for DTB from HCBD, which is a valuable and promising method for industrial production

No association between the vitamin D pathway gene polymorphisms and bone biomarkers response to calcium and low dose calcitriol supplementation in postmenopausal Chinese women: a one-year prospective study

<p><b>Introduction:</b> The aim of the study was to explore the association between the vitamin D pathway gene variations and the bone biomarkers response to calcium and low dose calcitriol supplementation in postmenopausal Chinese women.</p> <p><b>Methods:</b> A total of 110 healthy postmenopausal Chinese women (61.51 ± 6.93 years) were enrolled. The participants were supplemented with calcium (600 mg/d) and calcitriol (0.25 μg/d), for 1 year. Four biomarkers, serum levels of beta C-terminal cross-linked telopeptides of type I collagen (β-CTX), amino-terminal propeptide of type I collagen (P1NP), parathyroid hormone (PTH) and 25-hydroxyvitamin D [25(OH)D] were measured at baseline and 12-month follow-up. Multivariate regression models were established to explore the statistical association between the change rate of the four biomarkers and 15 key genes within the vitamin D metabolic pathway.</p> <p><b>Results:</b> This exclusion process left 98 participants for analysis. Serum levels of P1NP, β-CTX and PTH were significantly decreased at the 12-month follow-up (all <i>p</i> < 0.05). Serum 25(OH)D level had no significant change (<i>p</i> > 0.05). No association was found between the vitamin D pathway gene polymorphisms and bone biomarkers response to calcium and low dose calcitriol supplementation.</p> <p><b>Conclusions:</b> Genetic background of postmenopausal Chinese women might not influence supplemental response of the biomarkers to calcium and low dose calcitriol.</p