Designed Iron Catalysts for Allylic C−H Functionalization of Propylene and Simple Olefins

Abstract

Propylene gas is produced worldwide by steam cracking on million-metric-ton scale per year. It serves as a valuable starting material for π-bond functionalization but is rarely applied in transition metal-catalyzed allylic CÀ H functionalization for fine chemical synthesis. Herein, we report that a newly-developed cationic cyclopentadienyliron dicarbonyl complex allows for the conversion of propylene to its allylic CÀ C bond coupling products under catalytic conditions. This approach was also found applicable to the allylic functionalization of simple α-olefins with distinctive branched selectivity. Experimental and computational mechanistic studies supported the allylic deprotonation of the metal-coordinated alkene as the turnover-limiting step and led to insights into the multifaceted roles of the newly designed ligand in promoting allylic CÀ H functionalization with enhanced reactivity and stereoselectivity.

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

“…Our group has previously demonstrated that cyclo­penta­dienyl­iron(II) dicarbonyl complexes are capable of coordinating to and enhancing the C–H acidity of a range of unsaturated substrates, to facilitate the removal of protons at the allylic, propargylic, or allenic positions . As a result, functional group-tolerant amine and pyridine bases could be used for abstraction of the α-proton to deliver a nucleophilic organoiron species that could undergo subsequent electrophilic functionalization with predictable S E 2′ selectivity.…”

New Strategy for the Persistent Photocatalytic Reduction of U(VI): Utilization and Storage of Solar Energy in K+ and Cyano Co‐Decorated Poly(Heptazine Imide)

“…[ 50,51 ] In addition, the strong electron‐withdrawing cyano groups in K‐CN‐PHI also caused an enhanced electron paramagnetic resonance (EPR) signal (Figure 1d), revealing a much higher number of unpaired electrons within the π ‐conjugated structure. [ 52 ] The rearranged electronic structure make K‐CN‐PHI exhibits an obviously different micromorphology feature, as confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) (Figure S4, Supporting Information). Compared with PCN, which featured an irregular and multilayered structure (Figure S4a,c, Supporting Information), K‐CN‐PHI showed multiple separated sheets with a smaller particle size (Figure S4b,d, Supporting Information) and thereafter a higher Brunauer−Emmett−Teller (BET) surface area (93.50 m 2 g −1 , 5.9 times higher than PCN) (Figure S1c,d, Supporting information).…”

“…For K‐CN‐PHI, in addition to the electron transition of π → π * below 450 nm in the conjugated aromatic system, an additional absorption band in the region of 450–600 nm, which could be ascribed to the transition of n→ π * induced by lone‐pair electrons at N‐defect sites (C≡N), was observed. [ 52,54 ] The band structure of K‐CN‐PHI was also adjusted, with a slightly increased bandgap ( E g ) that is caused by the quantum confinement effect owing to the decreased interlayer distance (insert in Figure 2a). [ 55 ] Valence band (VB)‐XPS analysis (Figure 2b) revealed VB potentials ( E VB ) of 1.51 and 1.73 V (vs a normal hydrogen electrode [NHE], based on the formula in Supporting Information) for PCN and K‐CN‐PHI, respectively.…”

Recent DFT Calculations on the Mechanism of Transition‐Metal‐Catalyzed C−O Activation of Alcohols

“…Therefore, we suggest that the Grimme empirical D3 dispersion corrections (Becke‐Johnson‐damping or zero‐damping) [90,91] to be added when using functionals with poorly described noncovalent interactions such as B3LYP. For single‐point calculations, the Minnesota functionals such as M06 have become popular, and have been extensively used in transition metal catalyst systems (not limited to the current review paper) [92–97] . The PBE0 functional also performs well in describing metal‐catalysed systems, and is reliable in both geometry optimization and single‐point energy calculations while balancing computational accuracy and elapsed time.…”

“…For single-point calculations, the Minnesota functionals such as M06 have become popular, and have been extensively used in transition metal catalyst systems (not limited to the current review paper). [92][93][94][95][96][97] The PBE0 functional also performs well in describing metalcatalysed systems, and is reliable in both geometry optimization and single-point energy calculations while balancing computational accuracy and elapsed time. In addition, the double hybridization functionals such as ωB97X-V or ωB97M-V can bring higher accuracy when computational resources allow.…”