Abstract
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 SN 2 or double SN 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.
1 Homopropargylic Alcohols as Interesting Targets
2 A Diastereodivergent Synthesis of Homopropargylic Alcohols
2.1 Regioselective Ring-Opening of Acetylenic Oxiranes: A Challenge!
2.2 The Dramatic Influence of BF3 ·OEt2 Activation on the Regioselectivity
2.3 Nucleophilic Substitution with Retention of Configuration: Thanks to the Triple Bond
3 Laziness as a Good Motivation for Research: Design and Uses of a New Propargylic Carbenoid
3.1 Addition of Propargylic Carbenoids to Aldehydes: Dramatic Influence of Aldehyde on the Stereoselectivity
3.1.1 Highly Diastereoselective Access to Non-Aromatic Acetylenic Oxiranes
3.1.2 Unexpected Behavior of Aromatic Aldehydes: One or Two Transition States?
3.1.3 A New Propargylic Lithiocarbenoid: Curtin-Hammett Principle and Metallotropic Equilibrium
3.2 What About the Addition of Propargylzinc Carbenoids onto Imines?
3.2.1 Highly Diastereoselective Synthesis of Acetylenic N -Benzyl and N -H Aziridines
3.2.2 Unexpected Behavior of N -Sulfonylimines: Chelate versus Open Transition State?
3.2.2 En Route to the Stereoselective Synthesis of Enantiopure Acetylenic Aziridines
4 Conclusion and Perspectives
Key words
aziridines - carbenoids - epoxides - homopropargylic alcohols - zinc
