1,4-Hydroxybiradical Behavior Revealed through Crystal Structure-Solid-State Reactivity Correlations

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• 作者：Dario Braga ; Shuang Chen ; Heather Filson ; Lucia Maini ; Matthew R. Netherton ; Brian O. Patrick ; John R. Scheffer ; Carl Scott ; and Wujiong Xia
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：March 24, 2004
• 年：2004
• 卷：126
• 期：11
• 页码：3511 - 3520
• 全文大小：192K
• 年卷期：v.126,no.11(March 24, 2004)
• ISSN：1520-5126

文摘

Structure-reactivity correlations for triplet 1,4-hydroxybiradicals in solution are made difficult bythe presence of multiple reactive conformers and the possibility of conformation-dependent intersystemcrossing. These problems can be overcome by working in the crystalline state, where the conformationsof the 1,4-hydroxybiradicals are fixed and determinable by X-ray crystallography of the parent ketones,assuming that hydrogen atom abstraction occurs with little or no change in conformation. This approach isapplied to 15 bi- and tricyclic ketones designed to have slightly different biradical conformations, so thatthe effect of small and incremental changes in geometry on biradical behavior can be tested. The resultsindicate that, while geometry does have a strong influence on 1,4-hydroxybiradical partitioning betweencyclization, cleavage, and reverse hydrogen transfer, a full understanding of the results requires that thestrain involved in forming the cyclization products be taken into account.