Selective Formation of Functionalized α‑Quaternary Malononitriles toward 5,5-Disubstituted Pyrrolopyrimidinones

A modular, selective
approach to complex α-tertiary substituted
malononitriles is reported. The method takes advantage of β-ester-substituted
α,α-dinitrile alkenes as highly reactive, chemoselective
electrophiles for 1,4-additions with organometallic nucleophiles to
produce functionally and sterically dense all-carbon quaternary centers.
In the presence of a chiral ester auxiliary bearing an aromatic ring,
the 1,4-addition occurs with good to excellent selectivity due to
favorable cation−π interactions. The highly functionalized
malononitriles represent versatile building blocks and can be applied
toward efficient, highly selective syntheses of 5,5-disubstituted
pyrrolopyrimidinones.