Search results for "Ring strain"

Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp3)–H Arylation and Cyclopentene Synthesis through Strain Relea…

2021

A metal-free Hantzsch ester-mediated synthesis of cyclopentenylketones as well as γ-hetarylketones starting from ketocyclopropanes under eco-friendly conditions was developed. The versatility of the developed conditions is shown by reacting ketocyclopropanes in both a formal [3 + 2] cycloaddition with terminal alkynes (further investigated using theoretical calculations) and a radical C-C-coupling with cyanopyridines. The newly developed methodologies were later on utilized as a downstream reaction for photogenerated cyclopropanes combining UV and visible light photochemistry. Following this procedure, a UV-driven Norrish-Yang-type reaction induces the ring strain of the intermediates, whic…

2017

The title compound, C12H14Br2, was prepared by bromination/dehydrobromination ofE,E,Z-cyclododecatriene. The crystal is composed ofC2-symmetrical molecules with anEconformation of the bromoalkene fragments and nearly linear alkyne units. The torsion angles in the ring suggest significant ring strain.

Studien zum Vorgang der Wasserstoffübertragung, 52. Zur Kenntnis der elektroreduktiven Spaltung der N - N-Bindung

1978

Am Beispiel von 35 Hydrazinderivaten wird die elektroreduktive Spaltung polarographisch und praparativ untersucht. Es wurde gefunden: 1) Beim mono-, tri- und tetrabenzoylierten Hydrazin 9, 11 bzw. 12 verschiebt sich das Potential proportional der Anzahl der Benzoylgruppen nach positiveren Werten. Beim symmetrischen 1,2-Dibenzoylhydrazin (10) wird das Halbstufenpotential E1/2 — bedingt durch H-Verbruckung und mesomere Stabilisierung — stark nach negativen Werten verschoben. — 2) Bei den cyclischen Hydrazinderivaten 14–16 werden die E1/2-Werte sowohl in Abhangigkeit von der Ringspaltung als auch durch cis-Fixierung der Benzoylgruppen noch zusatzlich nach positiveren Werten verlagert. — 3) Ube…

Effects of an eccentric training programme on hamstring strain injuries in women football players

2015

Summary Study aim: to test the hypothesis that an eccentric training programme applied on women football players would reduce the hamstring injury rate by improving thigh muscle balance and, particularly, hamstring strength. Material and methods: three football teams were recruited for this randomised controlled trial. They played in the first and second divisions in Spain. Players were randomised within clubs either to the intervention (eccentric exercises, n = 22) or control (control exercises, n = 21) groups, and randomisation was stratified according to previous history of thigh strains. The eccentric programme was divided into 3 phases, and each phase was composed of 7 weeks. Complianc…

How does a simulated soccer match affect regional differences in biceps femoris muscle architecture?

2017

Soccer is played by thousands of athletes across the globe and its participation increases the overall risk of injury, in particular, hamstring strain injuries (HSI). Biceps femoris (BF) has been shown to be involved the in 5 out of 6 HSI cases and risk factors including fatigue and short BF fascicle length (FL) have been identified. Furthermore, previous studies suggest that different muscle regions may undergo different strains during dynamic tasks, which could contribute to injury risk. The primary aim of this study was to evaluate the effects of a soccer match on regional differences in the BF muscle architecture. A secondary aim was to assess the reliability of the extended field of vi…