Bradsher cyclization

What is Bradsher cyclization?

The Bradsher cyclization, also known as the Bradsher reaction, Bradsher-type aromatic cyclodehydration, and Parham cyclization, was first reported by Bradsher in 1939. This acid-catalyzed cyclization reaction is commonly used for synthesizing various polycyclic aromatic compounds, particularly those in the phenanthrene series.

Bradsher cyclization
Bradsher cyclization

In addition, various functional groups attached to an aromatic ring have been shown to be suitable for acid-catalyzed cyclization, including ketones, aldehydes, aldehyde derivatives (such as acetals), nitriles, amino alcohols, carbinols, Grignard-reagent-converted nitriles, haloethers, olefins, olefin oxides, and glycols. Furthermore, this cyclization can also be induced by photoirradiation or a strong base.

Mechanism of reaction

Bradsher cyclization reaction


Charles K. Bradsher “Synthesis of Phenanthrene Derivatives. IV.1 9,10-Cyclopenteno- and 9,10-Cyclohexenophenanthrene
Journal of the American Chemical Society 1939 61 (11), 3131-3132
DOI: 10.1021/ja01266a044