Search

A novel Pd-catalyzed Ullmann-type homocoupling reaction of the Blaise reaction intermediate generated by the reaction of 2-bromo arylnitriles and a Reformatsky reagent has been developed for one-pot synthesis of enamino ester-functionalized biaryls 2 in good yields. The 2,2'-substituted enamine moieties of the coupling products could be cyclized under acidic conditions through the conjugate addition/deamination cascade to afford the seven-membered N-heterocyclics 3 with biaryl backbone in excellent yields. [ABSTRACT FROM AUTHOR]

The Pd-catalyzed oxidative olefin amination of the zinc bromide complex intermediate, formed by the sequential reaction of nitriles with a Reformatsky reagent and 1-alkynes, affords pyrrole derivatives in good to excellent yields. This tandem protocol provides a simple, efficient, and atom- and pot-economical way to quickly build polysubstituted NH-pyrroles starting from readily available reagents in a regiocontrolled manner with a broad substrate scope and high functional group tolerance. In contrast, the Pd-catalyzed oxidative olefin amination of an isolated α-vinyl-β-enamino ester did not proceed effectively, but the reaction efficiency can be restored by addition of n-BuZnBr or Zn(OAc)2, indicating the crucial role of the zinc complex in this transformation. The synthetic utility of this protocol is exemplified by the rapid synthesis of pyrrolophenanthrenes and pyranopyrrolones through selective Pd- and Cu-catalyzed C-C and C-O bond-forming reactions. [ABSTRACT FROM AUTHOR]

We report the novel use of a nitrile as a mediator to achieve the regioselective intermolecular addition of unstabilized zinc ester enolates (Reformatsky reagents) to 1-alkynes and 1,3-enynes. This reaction is made possible by a reversible addition of enolates to a nitrile (Blaise reaction), generating a zinc aza-enolate that, unlike zinc ester enolates, can add intermolecularly to 1-alkynes and 1,3-enynes. Subsequent removal of the nitrile through a retro-Blaise reaction generates the targeted addition product. This method is combined with a Diels--Alder reaction and subsequent oxidative aromatization, providing a tandem one-pot de novo construction of α-arylated alkanoates from Reformatsky reagents. [ABSTRACT FROM AUTHOR]

The intramolecular alkylative reactivity and N/C selectivity of the various Blaise reaction intermediates, which are formed from the reaction of the Reformatsky reagents with ω-chloroalkyl nitriles, did not reach the synthetic potential as an entry to exo-cyclic enaminoesters. To circumvent this issue, various additives were investigated, among which the addition of NaHMDS dramatically enhanced the reactivity and N/C selectivity. This modification provided a highly efficient route for the synthesis of various N-fused heterocyclic compounds, as it requires only two steps from nitriles. [ABSTRACT FROM AUTHOR]