Direct Comparison of the Response of Bicyclic Sultam and Lactam Dienes to Photoexcitation. Concerning the Propensity of Differing Bond Types to Bridgehead Nitrogen for Homolytic Cleavage

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• 作者：Leo A. Paquette ; Robert D. Dura ; Nathan Fosnaugh ; Marshall Stepanian
• 刊名：Journal of Organic Chemistry
• 出版年：2006
• 出版时间：October 27, 2006
• 年：2006
• 卷：71
• 期：22
• 页码：8438 - 8445
• 全文大小：219K
• 年卷期：v.71,no.22(October 27, 2006)
• ISSN：1520-6904

文摘

A convergent strategy has allowed access to bridgehead sultam 9 and the related carboxamides 10 and11. The synthetic routing proceeds via the coupling of a suitably constructed dienamine to eithero-iodobenzenesulfonyl choride or o-iodobenzoyl chloride to generate the amides. The application insequence of ring-closing metathesis and an intramolecular Heck reaction gave rise to advanced tricyclicintermediates. The final two steps involved bromination in liquid bromine and proper 2-fold dehydrobromination. The latter maneuver was best achieved with tetrabutylammonium fluoride in DMSO atelevated temperature. While the irradiation of 9 led principally via SO₂-N bond homolysis and [1,5]sigmatropic rearrangement to generate 37, 10 proceeded via disrotatory cyclization to the exo cyclobutene39, and 11 resisted photoisomerization. The inertness of 11 may stem from its distorted structural featureswhich force its conjugated diene double bonds to be rigidly oriented 32 out-of-plane. The unique abilityof the sulfonamide linkage to excited-state homolysis holds comparative interest.