Experimental and computational studies of anti-Bredt amidinium salts.

Experimental and computational investigations of anti-Bredt amidinium salts are presented. Calculations show that the pyramidalization of an amino group can significantly destabilize the formal carbocation center of amidiniums, due to the decreased π donation. In some cases, the unfavorable -I effect of nitrogen surpasses its beneficial +M effect, and amidiniums become less stable than iminiums.

Activation of a σ-SnSn bond at copper, followed by double addition to an alkyne.

Many synthetically useful copper-catalyzed transformations involve the activation of apolar or weakly polar σ-bonds (E-H and E-E' bonds, with E = C, B, Si, Sn, etc.). Yet, little is known so far about the associated elementary steps, and it is highly desirable to gain better knowledge regarding the way σ-bonds can be activated by copper to help further development in this area.

Direct involvement of the acetato ligand in the reductive elimination step of rhodium-catalyzed methanol carbonylation.

For the last step of rhodium-catalyzed methanol carbonylation, high-pressure NMR, and kinetic and experimental data supported by density functional theory calculations are consistent with substitution of I(-) by an AcO(-) ligand on the [RhI(3)(COCH(3))(CO)(2)](-) species followed by reductive elimination of acetic anhydride, which immediately reacts with water to afford acetic acid.