Alkenes as Alkyne Equivalents in Radical Cascades Terminated by Fragmentations: Overcoming Stereoelectronic Restrictions on Ring Expansions for the Preparation of Expanded Polyaromatics
作者:Rana K. Mohamed、Sayantan Mondal、Brian Gold、Christopher J. Evoniuk、Tanmay Banerjee、Kenneth Hanson、Igor V. Alabugin
DOI:10.1021/jacs.5b02373
日期:2015.5.20
Chemoselective interaction of aromatic enynes with Bu3Sn radicals can be harnessed for selective cascade transformations, yielding either Sn-substituted naphthalenes or Sn-indenes. Depending on the substitution at the alkene terminus, the initial regioselective 5-exo-trig cyclizations can be intercepted at the 5-exo stage via either hydrogen atom abstraction or C-S bond scission or allowed to proceed
Drawing from a Pool of Radicals for the Design of Selective Enyne Cyclizations
作者:Sayantan Mondal、Rana K. Mohamed、Mariappan Manoharan、Hoa Phan、Igor V. Alabugin
DOI:10.1021/ol4028072
日期:2013.11.15
Despite the possibility of intermolecular attack at four different locations, the Bu3Sn-mediated radical cyclization of aromatic enynes is surprisingly selective. The observed reaction path originates from the least stable of the equilibrating pool of isomeric radicals produced by intermolecular Bu3Sn attack at the pi-bonds of substrates. The radical pool components are kinetically self-sorted via 5-exo-trig closure, the fastest of the four possible cyclizations. The resulting Sn-substituted indenes are capable of further transformations in reactions with electrophiles.