Copper(ll) Activation of Nitrite: Nitrosation of Nucleophiles and Generation of NO by Thiols

摘要

Nitrite (NO_2~-) and nitroso compounds (E-NO, E = RS, RO, and R_2N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper(ll) nitrito complex [Cl_2NN_(F6)]Cu(κ~2-O_2N)-THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu~(II)] (κ~2-O_2N) that leads to S-nitrosation to give the S-nitrosothiol RSNO and copper(ll) hydroxide [Cu~(II)]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph_2NH and alcohol ~tBuOH to give Ph_2NNO and ~tBuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper(II) thiolate [Cu~(II)]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu~(II)]-OH.