Reaktive E=C(p—p)π-Systenie, XIX. F₃CP=C(H)F und F₃CP = C(D)F als Dienophile / Reactive E=C(p—p)π-Systems, XIX. F₃CP=C(H)F and F₃CP=C(D)F as Dienophiles

Abstract

A study of the dienophilic properties of F3CP = C(H)F (1) and F3CP = C (D)F (4) has been performed by using Me3SnP(CF3)CF2H (2) and Me3SnP(CF3)CF2D (3), respectively, as precur­ sors for the in situ generation of 1 and 4 in the presence of 2 ,3-dim ethyl-1,3-butadiene, 1,3-cyclohexadiene or 9,10-dimethylanthracene. Slow elimination of Me3SnF occurs at 55 °C yielding the cycloadducts of 1 and 4, respectively, within 5 or 7 days. Polymerization is observed as the main stabilizing reaction of 1 and 4, thus reducing the yields o f the [2+4]-cycloadducts 5 to 9 to about 20%. They are formed as mixtures o f diastereomers in the ratio a:b ≈ 90:10. In the preferred isomer a according to NMR data CF3 and F have anti positions. Since NMDO calculations yield energy barriers of about 40 kcal/mol for E/Z isomerization, and literature values for inversion barriers of trialkyl phosphanes are of the same magnitude, the formation of isomers most likely has to be explained by a nonconcerted mechanism of the [2 + 4]-cycloaddition.

Electrocrystallization and electrochemical control of crystal growth: fundamental considerations and electrodeposition of metals

“…The data [17] may be analysed by plotting the increase in current density vs the square of the time interval ( tt ) 2 or (as shown in figure 4(b)), (jjmin)'I2 versus tr. The 221 (24) linear dependence at high overpotentials indicates instantaneous nucleation according to equation ( 22), followed by three-dimensional growth under charge transfer control. The relatively small dependence of the steady state current density upon overpotential may suggest that overlap of growth centres and formation of a continuous layer are followed by a thickening process which is partially mass transport controlled.…”

The chemistry of fluorine containing phosphaalkenes, arsaalkenes and selenocarbonyls

“…A thermodynamically directed 1,3-fluorine migration occurs to yield F 3 CP(F)-C(CF 3 )¼CF 2 , thus replacing the labile PC by a more stable CC double bond. There is a clear tendency for the Me 3 SnF elimination in stannyl-phosphanes Me 3 SnP(CF 3 )R F , whereby, in all cases investigated till now, the F atom is eliminated from the R F group, thus leaving the CF 3 -group unchanged [19][20][21].…”

“…A special advantage of this method is the easy preparation of Diels-Alder adducts even of very labile phosphaalkenes like F 3 CP¼C(F)H, MeP¼CF 2 , EtP¼CF 2 , Me 2 NP¼CF 2 etc. [21][22][23].…”

“…Compounds of type A are normal phosphaalkenes; they react with proton acidic agents like HCl, HBr, ROH and HNR 2 exclusively with formation of P(X)-C(H) derivatives and act as highly reactive dienophiles in [4 þ 2] cycloadditions with 1,3-dienes [18,19,21]. Representatives of type B are nearly non-polar and in reactions with HX, depending on the acidity or basicity of the reactants, regioselectively yield addition products with either PH-or PX-units.…”

Willingness to pay for flood risk mitigation among residents living near river’s confluence in Yogyakarta, Indonesia

“…After providing this justification, Scawthorn et al, (2006) [16] contend that in order to estimate building damage from flood damage, the damage module needs two inputs: the occupancy type of the building and the elevation of the first floor, which typically includes the design level; and flood depth. These elements are required for this research since its focus is on the impact of flooding rather than calculating the overall damage caused by flood hazards.…”