1 research outputs found
Nucleophile-Catalyzed Additions to Activated Triple Bonds. Protection of Lactams, Imides, and Nucleosides with MocVinyl and Related Groups
Additions
of lactams, imides, (<i>S</i>)-4-benzyl-1,3-oxazolidin-2-one,
2-pyridone, pyrimidine-2,4-diones (AZT derivatives), or inosines to
the electron-deficient triple bonds of methyl propynoate, <i>tert</i>-butyl propynoate, 3-butyn-2-one, <i>N</i>-propynoylmorpholine, or <i>N</i>-methoxy-<i>N</i>-methylpropynamide in the presence of many potential catalysts were
examined. DABCO and, second, DMAP appeared to be the best (highest
reaction rates and <i>E/Z</i> ratios), while RuCl<sub>3</sub>, RuClCp*(PPh<sub>3</sub>)<sub>2</sub>, AuCl, AuCl(PPh<sub>3</sub>), CuI, and Cu<sub>2</sub>(OTf)<sub>2</sub> were incapable of catalyzing
such additions. The groups incorporated (for example, the 2-(methoxycarbonyl)ethenyl
group that we name MocVinyl) serve as protecting groups for the above-mentioned
heterocyclic CONH or CONHCO moieties. Deprotections were accomplished
via exchange with good nucleophiles: the 1-dodecanethiolate anion
turned out to be the most general and efficient reagent, but in some
particular cases other nucleophiles also worked (e.g., MocVinyl-inosines
can be cleaved with succinimide anion). Some structural and mechanistic
details have been accounted for with the help of DFT and MP2 calculations