Diastereoselective Cyclopropanation of Terminal, Nonconjugated Alkenes with 2-Oxoethylpyridinium Salts via Nucleopalladation

A highly diastereoselective Pd(II)-catalyzed cyclopropanation of terminal, nonconjugated alkenes using 2-oxoethylpyridinium salts as a "carbenoid" source is reported. An AQ-directed nucleopalladation reaction followed by oxidative ring closure and reductive elimination steps results in the formation of a three-membered ring rather than the generation of [3+2] cycloaddition products. The process allows for the ready reaction of a range of 2-oxoethylpyridinium salts with simple olefins and provides an efficient means for the construction of syn-disubstituted cyclopropanes. The protocol is operationally straightforward, scalable and applicable to a wide range of substrates.