Aminomercuration-oxidation

Six-membered Rings Containing Two Nitrogens.- 5-Methyl-2,3-di-hydropyrazines (348) can be prepared effic iently in a one-pot oxidative aminomercuration procedure, starting from propargylic... 

The aminomercuration-demercuration reaction has provided two examples for primary to secondary amine conversion.In one, Markovnikov addition of the aminomercurial (10) to an alkene, followed by ligand exchange with sodium hydroxide and subsequent reduction with sodium borohydride, yields the secondary amine (11) in a one-pot reaction (Scheme 10). In the other,vicinal diamines (12) are the products from the one-pot reaction of alkenes with tetrafluoroboric acid and mercury(ll) oxide in the presence of excess primary amine (Scheme 11). Both reactions work equally well with secondary amines. 

Next, exposure of 255 to trifluoroacetic acid resulted in rearomatization of the A ring of morphine and cleavage of the carbamate (256), which prepared the substrate for the intended hydroamination and elaboration of the D ring of the title compound. All attempts failed to achieve ring closure from 255, either via aminomercuration or addition of lithium amide, and the material was converted to the corresponding tosyl amide before the ethylamino bridge was established. The cyclization was accomplished by addition of lithium to 257 and delivered the desired product in excellent yield. Oxidation of the secondary alcohol with benzophenone and t-BuOK allowed the isolation of e t-hydromorphone (258) in 12 steps from p-bromoethylbenzene. 

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