Synthesis, characterization and comparison of group 14 pyrrolides and indolides Ph 3MX (M = Si, Ge, Sn; X = C 4H 4N, C 8H 6N)

Abstract

The biologically important heterocycles pyrrole, C 4H 4N, and indole, C 8H 6N, ought to be useful as reagents in organic synthesis. Unfortunately, working with them has proved to be difficult because they tend to self-polymerize in solution, especially in the presence of acid catalysts. When the self-polymerization can be controlled, however, the pyrrole and indole units should provide an important route to selective N-metal binding, particularly when these ligands are activated by alkyl-lithium reagents. Using this approach, a general synthesis of the group 14 pyrrolides and indolides, Ph 3MX (M = Si, Ge, Sn; X = C 4H 4N, C 8H 6N), has been developed and the results are reported here. The compounds are formed as high-melting, white crystalline solids and have been characterized by 13C-, 29Si- and 119Sn-NMR, Raman and electron-impact mass spectroscopy as well as elemental analysis. A single-crystal X-ray study of Ph 3Si(C 4H 4N) has shown that the compound is disordered in the tetragonal lattice, even at low temperature (100 K).