The Regioselective Methylation of Polycyclic Aromatic Hydrocarbons through Tricarbonylchromium Coordination

Abstract

Deprotonation, methylation, and air oxidation of polycyclic arenes coordinated to chromium(0), (η6‐arene)Cr(CO)3, produced ring‐methylated products with high selectivity and in good yield. This procedure gave 3‐methylbenz[a]anthracene from (η6‐benz[a]anthracene)Cr(CO)3, 3‐methylphenanthrene from (η6‐phenanthrene)Cr(CO)3, 2‐acetyl‐6‐methylphenanthrene from (η6−2‐acetylphenanthrene)Cr(CO)3, and 3,7,12‐trimethylbenz[a]anthracene from (η6−7,12‐dimethylbenz[a]anthracene)Cr(CO)3.

The First Synthesis and Electronic Properties of Tetrakis[(hetero)phenanthrenyl]methanes

“…As would be expected, the absorption maxima of 9d were shifted bathochromically due to the more extended π‐system. In comparison with models taken for a single branch, such as phenanthrene ( 16 ),27−29 3‐methylphenanthrene ( 17 ),30,31 and chrysene ( 18 )28,32,33 the absorption maxima of the longest‐wavelength transitions of 9 were red‐shifted by Δ$\tilde {\nu}$ = 1600−2300 cm −1 , but showed similar structures (Figure 5). These bathochromic shifts were attributable to significant intramolecular electronic communication in the ground state.…”