Abstract
Organochromium(III) species are versatile nucleophiles in complex molecule synthesis due to their high functional group tolerance and chemoselectivity for aldehydes. Traditionally, carbonyl addition reactions of organochromium(III) species were performed through reduction of organohalides either using stoichiometric chromium(II) salts or catalytic chromium salts in the presence of stoichiometric reductants [such as Mn(0)]. Recently, alternative methods emerged involving organoradical formation from readily available starting materials (e.g., N-hydroxyphthalimide esters, alkenes, and alkanes), followed by trapping the radical with stoichiometric or catalytic chromium(II) salts. Such methods, especially using catalytic chromium(II) salts, will lead to the development of sustainable chemical processes minimizing salt wastes and number of synthetic steps. In this review, methods for generation of organochromium(III) species for addition reactions to carbonyl compounds, classified by nucleophiles are described.
1 Introduction
2 Alkylation
2.1 Branch-Selective Reductive Alkylation of Aldehydes Using Unactivated Alkenes
2.2 Linear-Selective Alkylation of Aldehydes
2.2.1 Catalytic Decarboxylative Alkylation of Aldehydes Using NHPI Esters
2.2.2 Catalytic Reductive Alkylation of Aldehydes Using Unactivated Alkenes
2.2.3 Alkylation of Aldehydes via C(sp3)–H Bond Functionalization of Unactivated Alkanes
2.3 Catalytic α-Aminoalkylation of Carbonyl Compounds
3 Allylation
3.1 Catalytic Allylation of Aldehydes via Three-Component Coupling
3.2 Catalytic Allylation of Aldehydes via C(sp3)–H Bond Functionalization of Alkenes
4 Propargylation: Catalytic Propargylation of Aldehydes via Three-Component Coupling
5 Conclusion
Key words
chromium - nucleophilic addition - aldehyde - photoredox catalyst - radical-polar crossover
