Diels–Alder Reactions of 9‑Ferrocenyl- and 9,10-Diferrocenylanthracene: Steric Control of 9,10- versus 1,4-Cycloaddition

Cycloadditions of benzynes, N-methyl- or N-phenylmaleimide, dimethyl acetylenedicarboxylate, and benzoquinone to 9-ferrocenylanthracene (1) and 9,10-diferrocenylanthracene (2) are described. Benzyne and 3-fluorobenzyne add to 1 and 2 to form the corresponding 9-ferrocenyl- or 9,10-diferrocenyltriptycenes; in contrast, bulkier benzynes such as 3-trifluoromethylbenzyne preferentially add to 2 across C1 and C4 to form …