Tetrahydroxydiboron-Initiated Atom-Transfer Radical Cyclization

In this work, the first diboron reagent initiated atom-transfer radical cyclization was reported, in which the boryl radicals were generated by the homolytic cleavage of a B-B single bond weakened by the coordination of Lewis base. To clarify the role of carbonate and DMF in the cleavage of B-B bond, we calculated the free energy diagram of two pathways by density functional theory (DFT) investigations. The DFT calculation showed that the presence of carbonate facilitates the B-B bond cleavage to form boron radicals which can be further stabilized by DMF. Subsequent atom transfer cyclization initiated by stabilized dihydroxyboron radical are also energetically favored.

A lutidine-promoted photoredox catalytic atom-transfer radical cyclization reaction for the synthesis of 4-bromo-3,3-dialkyl-octahydro-indol-2-ones

We describe an atom-transfer radical cyclization strategy, with which a variety of 4-bromo-3,3-dialkyl-octahydro-indol-2-one compounds can be easily accessed via a lutidine-promoted photoredox catalytic halo-alkylation of 1,6-dienes.