A C-H functionalization approach to diverse nitrogenous scaffolds through conjugate addition of catalytic allyliron nucleophiles.

Cyclopentadienyliron(ii) dicarbonyl complexes capable of coordinating to and enhancing the acidity of a range of unsaturated substrates have emerged as a new class of base-metal derived catalysts for C-H functionalization. In this manuscript, the iron-catalyzed C-H functionalization of allylic C(sp)-H bonds using nitrogen containing α,β-unsaturated carbonyl compounds as coupling partners is reported. Employing a cationic cyclopentadienyliron dicarbonyl complex, this redox neutral process converts simple alkenes into allylic anion equivalents for 1,4-addition into maleimides, acyclic α,β-unsaturated imides, and vinylogous amides.

Iron-Catalyzed Coupling of Alkenes and Enones: Sakurai-Michael-type Conjugate Addition of Catalytic Allyliron Nucleophiles.

The iron-catalyzed coupling of alkenes and enones through allylic C(sp)-H functionalization is reported. This redox-neutral process employs a cyclopentadienyliron(II) dicarbonyl catalyst and simple alkene substrates to generate catalytic allyliron intermediates for 1,4-addition to chalcones and other conjugated enones. The use of 2,4,6-collidine as the base and a combination of triisopropylsilyl triflate and LiNTf as Lewis acids was found to facilitate this transformation under mild, functional group-tolerant conditions.

Iron-Catalyzed Contrasteric Functionalization of Allenic C(sp)-H Bonds: Synthesis of α-Aminoalkyl 1,1-Disubstituted Allenes.

An iron-catalyzed C-H functionalization of simple monosubstituted allenes is reported. An efficient protocol for this process was made possible by the use of a newly developed electron-rich and sterically hindered cationic cyclopentadienyliron dicarbonyl complex as the catalyst and -sulfonyl hemiaminal ether reagents as precursors to iminium ion electrophiles. Under optimized conditions, the use of a mild, functional-group-tolerant base enabled the conversion of a range of monoalkyl allenes to their allenylic sulfonamido 1,1-disubstituted derivatives, a previously unreported and contrasteric regiochemical outcome for the C-H functionalization of electronically unbiased and directing-group-free allenes.