Samarium(II) iodide (SmI2) has been successfully utilized as a reducing agent for the intramolecular
coupling of ketones with nitriles. The use of visible light to promote the reductive coupling
represents an improvement over previously reported protocols. The procedure also avoids
overreduction of the resulting α-hydroxy ketones. Monocyclic, fused bicyclic, and bridged bicyclic
α-hydroxy ketones composed of a number of substitution patterns have been synthesized in moderate
to excellent yield via this method. A sequential reaction consisting of a nucleophilic acyl substitution
followed by a ketyl−nitrile coupling has also been accomplished.
ring closure reactions ring closure reactions O 0130
-053Intramolecular Ketone-Nitrile Reductive Coupling Reactions Promoted by Samarium(II) Iodide.-The photochemically induced reaction of keto nitriles of type (I), (III), and (V) with SmI 2 offers an efficient route to prepare monocyclic, fused bicyclic, and bridged α-hydroxy ketones. 5-exo-Coupling proceeds with better results than 6-exo-cyclization. A sequential reaction consisting of a nucleophilic acyl substitution followed by a ketyl-nitrile coupling is also possible. - (MOLANDER, GARY A.; WOLFE, CHAD N.; J. Org. Chem. 63 (1998) 24, 9031-9036; Dep. Chem. Biochem., Univ. Colo., Boulder, CO 80309, USA; EN)
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