Synthesis of 1,4-Phenanthrenequinones via Stannic Chloride-Induced Cyclizations

Substituted 1,4-phenanthrenequinones such as 1 are useful building blocks for the preparation of novel materials. Katz and others have shown that compounds such as 1 can be transformed into helicenes by DielsAlder reactions.1 Certain 1,4-phenanthrenequinones also have potential as synthetic intermediates for natural products synthesis. Additionally, some naturally occurring 1,4-phenanthrenequinones such as cypripedium (2) are biologically active.2 Kraus and Carpenter have determined that some 1,4-phenanthrenequinones exhibit inhibitory activity in vitro against the equine infectious anemia virus.3