Highly Diastereoselective Formal Nucleophilic Substitution of Bromocyclopropanes

Abstract

A highly diastereoselective formal nucleophilic substitution of bromocyclopropanes with oxygen- and nitrogen-based nucleophiles was demonstrated. The reaction proceeds via a base-assisted dehydrohalogenation producing a cyclopropene intermediate, which subsequently undergoes addition of a pronucleophile across the strained double bond. Very high chemoselectivity toward addition of primary and secondary alkoxides, as well as N-nucleophiles, in the presence of tert-butoxide base was observed, whereas phenoxides did not undergo addition under these reaction conditions. Facial selectivity of the addition can be efficiently controlled either by sterics or through a directing effect of an amide, carboxylate, and an o-aminomethylphenol function. Employment of tethered optically active amino alcohols as pronucleophiles allowed for efficient assembly of homochiral bicyclic compounds.