Tunable Metal-Catalyzed Heterocyclization Reactions of Allenic Amino Alcohols: An Experimental and Theoretical Study

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• 作者：Benito Alcaide ; Pedro Almendros ; Cristina Aragoncillo ; Gonzalo Gómez-Campillos ; M. Teresa Quirós ; Elena Soriano
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：September 2, 2016
• 年：2016
• 卷：81
• 期：17
• 页码：7362-7372
• 全文大小：612K
• 年卷期：0
• ISSN：1520-6904

文摘

Controlled preparation of 2,5-dihydro-1H-pyrroles, 3,6-dihydro-2H-pyrans, and pyrroles has been achieved through switchable chemo- and regioselectivity in the metal-catalyzed heterocyclization reactions of allenic amino alcohols. The gold-catalyzed cycloisomerization reaction of α-amino-β-hydroxyallenes was effective as 5-endo cyclization by addition of amino functionality to the distal allene carbon to yield enantiopure 2,5-dihydro-1H-pyrroles, whereas their palladium-catalyzed cyclizative coupling reactions furnished 3,6-dihydro-2H-pyrans through a chemo- and regioselective 6-endo cycloetherification. Conversely, the gold-catalyzed heterocyclization reaction of β-amino-γ-hydroxyallenes generated exclusively pyrrole derivatives. These results could be explained through a chemo- and regioselective 5-exo aminocyclization to the central allene carbon followed by aromatization. Chemo- and regioselectivity depend on both linker elongation as well as the type of catalyst. This behavior can be justified by means of density functional theory calculations.