Internal Chelation within Functionalized Organoindium Reagents: Prospects for Regio- and Stereocontrol in the Allylation, Propargylation and Allenylation of Carbonyl Compounds

Abstract

The low basicity, selective nucleophilicity, and mildness of organoindium compounds allow for the incorporation of many important yet sensitive functional groups into their structure, including examples capable of intramolecularly chelating the indium center within these reagents. The specific nature of such chelated organoindiums causes the reactions involving them to proceed in a unique manner, often with regio- and stereoselectivity inaccessible with simple organometallic reagents. This review covers the rare examples of regio- and stereoselective allylation, propargylation, and allenylation of carbonyl compounds with chelated organoindiums, including brief descriptions of the applications of the resulting adducts in the asymmetric synthesis of natural products and synthetic targets of biological and medicinal interest.1 Introduction2 Internal Chelation Control in the Allylation Processes2.1 Allylindiums with a Chelating Center at the γ-Position2.2 Allylindiums with a chelating Center at the δ-Position2.3 Allylindiums with a Chelating Center at ε- and ζ-Positions2.4 Allylindiums with a Chelating Center at γ′- and δ′-Positions3 Internal Chelation Control in Propargylation and Allenylation Processes­3.1 Additions of Chelated Allenylindiums3.2 Additions of Chelated Propargylindiums4 Conclusion

Enantioselective Ruthenium-BINAP-Catalyzed Carbonyl Reductive Coupling of Alkoxyallenes: Convergent Construction of syn-sec,tert-Diols via (Z)-σ-Allylmetal Intermediates

“…We posited that the enhanced oxaphilicity of ruthenium might enable asymmetric couplings to unactivated aldehydes. In the case of alkoxyallenes, such oxaphilicity might also result in internal chelation to form ( Z )-σ-allylmetal nucleophiles (Scheme ). , Hence, to accommodate aldehyde binding, such chelation must be reversible and, to preserve syn -diastereoselectivity, carbonyl addition must be fast relative to ( Z )-to-( E )-isomerization of the fluxional allylruthenium intermediates . Furthermore, as described by Marek, for γ,γ-disubstituted allylmetal nucleophiles gauche interactions associated with the developing C–C bond can reverse the equatorial vs axial preference of the aldehyde substituent to erode or invert diastereoselectivity.…”