Efficient Synthesis of Cyclopropylacetylene, a Crucial Synthetic Intermediate for Efavirenz (Sustiva™), a HIV-1 Reverse Transcriptase Inhibitor

Nolan R. Otto, Matthew W. Scales and Ralph N. Salvatore*

Southeastern University
Department of Natural Sciences
1000 Longfellow Blvd.
Lakeland, FL 33801

Cyclopropylacetylene (CA) has become an attractive synthetic target due to increasing demand as a building block for Efavirenz (Sustiva™), which is a potent inhibitor of the human immunodeficiency virus type-1 (HIV-1) nonnucleoside reverse transcriptase. Although a variety of syntheses have been reported, CA is the most expensive raw material as it uses combinations of toxic, difficult to handle reagents and results in incomplete conversions and low yields/purity, rendering the overall preparations inefficient. Thus, it is desirable to discover new routes to produce CA on a large scale that improve upon these limitations. In our laboratories, efficient syntheses of cyclopropylacetylene were achieved from either cyclopropyl methyl ketone or via an intramolecular ring closure of 5-chloro-1-pentyne in the presence of a strong base (cesium hydroxide). Different reaction pathways were investigated to avoid the concomitant formation of side products. In addition, to explore the versatility of these conditions, various heterocyclic analogs were also prepared.