ABSTRACT
Compared with the extensively reported hydrogen atom transfer (HAT) at sp3 C-H, abstraction of hydrogen atoms at the sp2 carbon is extremely rare. Here, we communicate the site-selective cyanation of the sp2 C-H bond of allenes using the strategy of copper-catalyzed radical relay. The reactions afford various allenyl nitriles directly from simple allenes with a broad substrate scope and a remarkable functional group compatibility under mild conditions. These reactions exhibit excellent site-selectivity toward sp2 C-H, which can be attributed to the unique pocket created by the Cu-bound nitrogen-centered radical. The favorable HAT on sp2 C-H is due to crucial hydrogen bonding between the fluoride bonded to the Cu(II) center and the hydrogen atom at the allylic position. These features enable the late-stage functionalization of druglike bioactive molecules containing an allene motif.
ABSTRACT
The temperature-dependent Henry's Law Constant for hydrogen peroxide was measured. The gas phase of hydrogen peroxide from the vapor saturator collected in a cryogenic trap was analyzed by a spectrophotometric determination, based on the oxidative decoloration of BPR (bromopryogallol red) reaction with hydrogen peroxide under the catalysis of hemin. At 10 degrees C - 35 degrees C, the relationship between Henry's Law constant K(H) (mol x L(-1) x atm(-1)) of hydrogen peroxide and temperature T (K) can be expressed as ln K(H) = a/T - b, where a = 7 269+/-22, and b = 13.26+/-0.08. The standard heat of hydrogen peroxide aqueous solution is 60.43+/-0.18 kJ x K(-1) x mol(-1).
