ABSTRACT
Zn(OTf)2 (OTf- = trifluoromethanesulfonate) catalyzes the silylation of pyridine, 3-picoline, and quinoline to afford the silylated products, where the silyl groups are meta to the nitrogen. The isolated yields of the products range from 41 to 26%. The 2- and 4-picolines yielded the silylmethylpyridines, where the CH3 groups were silylated instead of the ring. The pyridine silylation can occur via two separate pathways, involving either a 1,4- or a 1,2-hydrosilylation of pyridine as the first step. A byproduct of the pyridine silylation is a head-to-tail dimerization of N-silyl-1,4-dihydropyridine to form a diazaditwistane molecule.
ABSTRACT
The reactions between H(2)dc3 and Co(acac)(3) have been studied in the presence and absence of base. In the presence of base, a complex with an intramolecular Co-C bond, Co(dc3-C-(8))(H(2)O), 1, is formed, presumably through heterolytic C-H bond activation. An X-ray crystallographic study demonstrates the presence of a Co-C bond and shows that the diazacyclooctane (daco) subunit adopts the chair-boat conformation with respect to the metal. The cobalt-carbon bond induces strain in the macrocycle as demonstrated by bond angles significantly deviating from tetrahedral. The (13)C NMR resonance of the carbon atom bound to cobalt (-10.5 ppm) suggests significant ionic character in the cobalt-carbon bond. However, we were unable to cleave this bond in the presence of strong acid. In the absence of base, the reaction of Co(acac)(3) with H(2)dc3 resulted in C-N cleavage of the ligand and the formation of a complex of dioxocyclam, Co(dc)(acac), 2. This complex has subsequently been prepared in high yield by the reaction of Co(acac)(3) with dioxocyclam. An X-ray crystallographic study demonstrates that dioxocyclam adopts the heretofore unreported cis configuration, having folded along a N-Co-N axis that is perpendicular to the Co-acac plane.
