Highly diastereoselective syntheses of propargylic acid and homopropargylic systems

The results of our research dealing with the stereoselective synthesis of propargylic and homopropargylic systems are summarized. In a first part, the stereoselective formation of syn- or anti-disubstituted homopropargylic alcohols from acetylenic oxiranes through S(N)2 or double S(N)2' has been developed. Thus, the two diastereomers of a given homopropargylic alcohol are stereospecifically available. The great impact of Lewis acid activation on the regioselectivity of the ring-opening reactions of propargylic oxiranes is also detailed. In a second part, the preparation and uses of new acetylenic/allenic carbenoids are overviewed; their reactivity towards carbonyl compounds and imines is examined, leading to the highly stereoselective synthesis of acetylenic chlorohydrins, oxiranes and aziridines.