Polar Radical Pair Pathway To Assemble the Pyrimidinone Core of the HIV Integrase Inhibitor Raltegravir Potassium

Break up to make up: Combined experimental and computational studies provide evidence that the key step in the synthesis of a novel anti‐HIV drug involves an unprecedented stepwise radical pair rearrangement mechanism in which radical fragments are held together by strong electrostatic forces (see scheme); this is favored over alternative mechanisms involving concerted pericyclic rearrangement.