Photochemical [2 + 2] cycloaddition reactions of 6-alkenyl-3-phenylcyclohex-2-en-1-ones: using biradical conformation control to account for exceptions to the “rule of five”
Photochemical [2 + 2] cycloaddition reactions of 6-alkenyl-3-phenylcyclohex-2-en-1-ones: using biradical conformation control to account for exceptions to the “rule of five”
Photochemical [2 + 2] cycloaddition reactions of 6-alkenyl-3-phenylcyclohex-2-en-1-ones: using biradical conformation control to account for exceptions to the “rule of five”
作者:Stephen A. Bradley、Brian J. Bresnan、Sylvia M. Draper、Niall W. A. Geraghty、Mark Jeffares、Thomas McCabe、T. Brian H. McMurry、John E. O'Brien
DOI:10.1039/c0ob01131b
日期:——
A series of 6-alkenyl-3-phenylcyclohex-2-enones has been synthesised and the structures of the products obtained from them on irradiation have been determined. The 6-propenyl compounds afforded a tricyclic âparallelâ [2 + 2] cycloaddition product and a bicyclic enone resulting from hydrogen abstraction in the biradical intermediate. The 6-butenyl and 6-pentenyl analogues gave âcrossedâ cycloaddition products only. Although the regiochemistry of these cycloaddition reactions cannot be explained in terms of the ârule of fiveâ, it is compatible with the concept of âbiradical conformation controlâ which is based on a consideration of the energy and structure of the possible 1,4-biradical intermediates.