Transition metal catalysed borylation of C-H bonds

Chapter one provides a general review of the metal catalysed diboration of alkynes, 1,2- and 1,3-dienes, a,ß-unsaturated carbonyl compounds, and alkenes, as well as the metal catalysed borylation of alkane and arene C-H bonds. Chapter two is divided into two main sections. The first section introduces a high yield, highly selective catalytic synthesis of vinylboronate esters VBEs, including 1,1-disubstituted VBEs, from alkenes without significant hydrogenation or hydroboration, using the catalyst precursor, trans- [RҺС1(СО)(РРhз)2], and the diboron reagents В2РІП2, В2ПЄОР2 and HBpin. The second section addresses the synthesis of VBEs via microwave-assisted catalysis and these results are compared with those from the conventional, thermal reactions. Chapter three investigates regioselectivity in the synthesis of pyridinyl and bipyridinyl botónate esters via C-H activation using the catalyst precursor, [Іг(СОВ)(ц-ОМе)]2, and 4,4'-'Bu2-2,2'-bipyridine as the ligand. Several the pyridinyl and bipyridinyl boronate esters were coupled with aryl halides by Suzuki-Miyaura cross-coupling reactions in one pot. Examples include msiture-sensitve heteroaryl 2-boronate esters. Chapter four shows the utility of the transition metal catalysed borylation of C-H bonds in the synthesis of biologically active retinoic acid analogs

High-pressure neutron study of the morphotropic PZT: phase transitions in a two-phase system

In piezoelectric ceramics the changes in the phase stabilities versus stress and temperature in the vicinity of the phase boundary play a central role. The present study was dedicated to the classical piezoelectric, lead-zirconate-titanate (PZT) ceramic with composition Pb(Zr$_{0.54}$Ti$_{0.46}$)O$_3$ at the Zr-rich side of the morphotropic phase boundary at which both intrinsic and extrinsic contributions to piezoelectricity are significant. The pressure-induced changes in this two-phase (rhombohedral $R3c$+monoclinic $Cm$ at room temperature and $R3c+P4mm$ above 1 GPa pressures) system were studied by high-pressure neutron powder diffraction technique. The experiments show that applying pressure favors the $R3c$ phase, whereas the $Cm$ phase transforms continuously to the $P4mm$, which is favored at elevated temperatures due to the competing entropy term. The $Cm\rightarrow R3c$ phase transformation is discontinuous. The transformation contributes to the extrinsic piezoelectricity. An important contribution to the intrinsic piezoelectricity was revealed: a large displacement of the $B$ cations (Zr and Ti) with respect to the oxygen anions is induced by pressure. Above 600 K a phase transition to a cubic phase took place. Balance between the competing terms dictates the curvature of the phase boundary. After high-pressure experiments the amount of rhombohedral phase was larger than initially, suggesting that on the Zr-rich side of the phase boundary the monoclinic phase is metastable.Comment: 6 figure

Photocatalytic Degradation of Methylene Blue by Fe/ZnO/SiO 2

The photocatalytic activity of Fe/ZnO/SiO2 catalysts under visible-light irradiation for the degradation of methylene blue was evaluated. The effect of pH, illumination time, amount of catalyst loaded, and initial dye concentration on the degradation efficiency of methylene blue was investigated. The results reveal that the optimum photocatalytic oxidation conditions of methylene blue are as follows: pH=4 and illumination time is 30 min, the amount of catalyst loading is 0.075 g/L and 50 ppm methylene blue dye concentration. Under these conditions, the removal efficiency of methylene blue was 100%

Rhodium catalysed dehydrogenative borylation of alkenes: Vinylboronates via C-H activation

We present herein a high yield, highly selective catalytic synthesis of vinylboronate esters (VBEs), including 1,1-disubstituted VBEs, from alkenes without significant hydrogenation or hydroboration, using the simple catalyst precursor, trans-[RhCl(CO)(PPh3)(2)] (1), and the diboron reagents B(2)pin(2) (2a, pin = pinacolato = OCMe2CMe2O) or B(2)neop(2) (2b, neop = neopentylglycolato = OCH2CMe2CH2O), or the monoboron reagent HBpin, all of which are commercially available. The reactions were conducted at 80 degrees C using conventional heating, or in a microwave reactor at 150 degrees C

Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse

This article is also available through American Chemical Society Authorchoice Open Access at http://dx.doi.org/10.1021/acs.chemrev.6b00193Although known for over 90 years, only in the past two decades has the chemistry of diboron(4) compounds been extensively explored. Many interesting structural features and reaction patterns have emerged, and more importantly, these compounds now feature prominently in both metal-catalyzed and metal-free methodologies for the formation of B-C bonds and other processes.T.B.M. thanks the DFG and the University of Würzburg for support. S.A.W. thanks Chris Vogels for helpful discussions and NSERC of Canada for support