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  • Title: The scope and limitations of 1,3-stannyl shift-promoted intramolecular cyclizations of alpha-stannyl radicals with a formyl group.
    Author: Ueng SH, Chen MJ, Chu SF, Shao YF, Fan GT, Chang SY, Tsai YM.
    Journal: J Org Chem; 2006 Feb 17; 71(4):1502-12. PubMed ID: 16468799.
    Abstract:
    Alpha-tributylstannyl radicals can be generated from the corresponding bromides or xanthates. These radicals undergo efficient intramolecular 1,5-cyclizations with a formyl group. The resulting beta-stannyl alkoxy radicals proceed through a 1,3-stannyl shift from carbon to oxygen to afford beta-stannyloxy radicals. This novel rearrangement is most likely irreversible and serves as a driving force to promote the cyclizations. Although the cyclization rates can be accelerated when the formyl group carries alpha-dimethyl substituents, unfortunately beta-scission of the alkoxy radicals becomes competitive with the 1,3-stannyl shift. The beta-stannyloxy radicals can be employed in further cyclizations to obtain tandem cyclization products.
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