IMIDYL RADICALS - FREE-RADICAL ADDITION OF N-BROMOIMIDES TO ALKENES

N-Bromoimides 1 add to alkenes 3 in a free-radical chain reaction on a multigram scale with imidyl radicals 2 as chain carriers. High regioselectivities are found when the substituents at the non-attacked sp2 carbon atom to the alkene 3 are alkoxy or sterically bulky residues, The stereochemistry of the addition is determined by the bromine transfer from the N-bromoimide 1 to the adduct radical 4. Formation of the trans-addition products 5 is favored. In competition reactions vinyl ethers react faster with the imidyl radicals 2 than alkyl-substituted alkenes.