Allenylation and Propargylation Reactions of Ketones, Aldehydes, Imines, and Iminium Ions Using Organoboronates and Related Derivatives

Abstract

Allenyl- and propargylboronates have emerged as versatile reagents to effect regioselective propargylation or allenylation reactions of aldehydes, ketones, imines, and iminium ions. These boron-­derived reagents have the ability to undergo transmetalation reactions with other metals (Ag, Cu, In, and Zn), often using only catalytic amounts of these metals, leading to more facile and highly regioselective reactions. Enantioselective organocatalyzed reactions have also been developed using, chiral diols, aminophenols, and phosphoric ­acids. This short review highlights recent developments in this area. 1 Introduction 2 Synthesis of Homopropargylic and α-Allenyl Alcohols 2.1 Direct Synthesis of Racemic Homopropargylic and α-Allenyl ­Alcohols 2.2 Metal-Catalyzed Synthesis of Racemic Homopropargylic and α-Allenyl Alcohols 2.3 Enantioselective Synthesis of Homopropargylic Alcohols Using Chiral Allenylboronates 2.4 Enantioselective Synthesis of Homopropargylic Alcohols and α-Allenyl Alcohols Using Chiral Organocatalysts 2.5 Metal-Catalyzed Enantioselective Synthesis of Homopropargylic and α-Allenyl Alcohols 3 Synthesis of Homopropargylic and α-Allenyl Amines 3.1 Direct Synthesis of Homopropargylic Amines from Imines and Iminium Ions 3.2 Metal-Catalyzed Synthesis of Racemic Homopropargylic and α-Allenyl Amines 3.3 Enantioselective Synthesis of α-Allenyl Amines Using Catalytic Amounts of a Chiral Aminophenol 3.4 Metal-Catalyzed Diastereoselective Synthesis of Chiral Homopropargylic and α-Allenyl Amines from Chiral <i>N</i>-<i>tert</i>-Butylsulfinylimines 3.5 Metal-Catalyzed Enantioselective Synthesis of Chiral Homopropargylic and α-Allenyl Amines 4 Applications to Synthesis 5 Conclusions