Caroline Meyers

Dual effect of halides in the Stille reaction: in situ halide metathesis and catalyst stabilization.

Halide anions can increase or decrease the transmetallation rate of the Stille reaction through in situ halide metathesis. Although the influence of the halogen present in oxidative addition complexes on the transmetallation rate with organostannanes was already known, the application of in situ halide metathesis to accelerate cross-coupling reactions with organometallic reagents is not described in the literature yet. In addition a second unprecedented role of halides was discovered. Halide anions stabilize the [Pd(0)(L)(2)] catalyst in Stille reactions, by means of [Pd(0)X(L)(2)](-) formation (X=Cl, I), hereby preventing its leaching from the catalytic cycle. Both arene (iodobenzene) and azaheteroarene (2-halopyridine, halopyrazine, 2-halopyrimidine) substrates were used.

Synthesis of 6-methyl-6**H**-indolo[3,2-**c**]isoquinoline and 6-methyl-6**H**-indolo[2,3-**c**]isoquinoline: two new unnatural isoquinoline isomers of the cryptolepine series

Abstract 11H-indolo[3,2-c]isoquinoline has been synthesized in two steps starting from 4-bromoisoquinoline and 2-bromoaniline via a selective Buchwald–Hartwig reaction followed by a Pd-catalyzed intramolecular direct arylation involving C(sp2)–H activation. The synthesis of 7H-indolo[2,3-c]isoquinoline was achieved by a combination of a Suzuki reaction with an intramolecular nitrene insertion reaction starting from 4-bromoisoquinoline and {2-[(2,2-dimethylpropanoyl)amino]phenyl}boronic acid. Selective methylation of the tetracyclic skeletons yielded the title compounds 6-methyl-6H-indolo[3,2-c]isoquinoline and 6-methyl-6H-indolo[2,3-c]isoquinoline, which have never been described in the literature before.