On Pentakis(pentafluoroethyl)stannate, [Sn(C2 F5 )5 ]− , and the Gas-Free Generation of Pentafluoroethyllithium, LiC2 F5

Current State of Microflow Trifluoromethylation Reactions

The trifluoromethyl group is a powerful structural motif in drugs and polymers; thus, developing trifluoromethylation reactions is an important area of research in organic chemistry. Over the past few decades, significant progress has been made in developing new methods for the trifluoromethylation of organic molecules, ranging from nucleophilic and electrophilic approaches to transition-metal catalysis, photocatalysis, and electrolytic reactions. While these reactions were initially developed in batch systems, more recent microflow versions are highly attractive for industrial applications owing to their scalability, safety, and time efficiency. In this review, we discuss the current state of microflow trifluoromethylation. Approaches for microflow trifluoromethylation based on different trifluoromethylation reagents are described, including continuous flow, flow photochemical, microfluidic electrochemical reactions, and large-scale microflow reactions.

Copper-mediated pentafluoroethylation of organoboronates and terminal alkynes with TMSCF3

The TMSCF₃-derived CuCF₂CF₃ species has been successfully applied in pentafluoroethylation of organoboronates and terminal alkynes. By using 1,10-phenanthroline as a ligand, a broad range of (hetero)arylboronates and alkenylboronates were smoothly pentafluoroethylated under aerobic conditions. Furthermore, terminal alkynes can undergo aerobic cross-coupling with the TMSCF₃-derived CuCF₂CF₃ species in the absence of additional ligands.

Pentafluoroethylation of Carbonyl Compounds Using HFC-125 in a Flow Microreactor System

The protocol of micro-flow nucleophilic pentafluoroethylation using pentafluoroethane (HC₂F₅, HFC-125), a nontoxic, inexpensive, and commercially available greenhouse gas, is described. The micro-flow pentafluoroethylation by HFC-125 proceeded smoothly at room temperature or at -10 °C in DMF or toluene in the presence of a potassium base, namely, t-BuOK or KHMDS. A broad range of ketones, aldehydes, and chalcones with various substituted benzene rings were successfully converted to the corresponding pentafluoroethyl carbinols instantly with good to high yields.

Pentafluoroethylation of Carbonyl Compounds by HFC-125 via the Encapsulation of the K Cation with Glymes

A simple protocol to overcome the explosive pentafluoroethylation of carbonyl compounds by HFC-125 is described. The use of potassium (K) bases with triglyme or tetraglyme as a solvent safely yields the pentafluoroethylation products in good to high yields. The experimental results suggest that an encapsulation of the K cation by glymes as K(glyme)₂ inhibits the contact between the K cation and the reactive anionic pentafluoroethyl counterion, preventing their transformation into KF and explosive tetrafluoroethylene (TFE). The generation of sterically demanding [K(G3)₂]⁺ and [K(G4)₂]⁺ is an effective way as an unstable pentafluoroethyl anion reservoir.

Pentafluoroethylated Compounds of Silicon, Germanium and Tin

In this contribution we present an account on pentafluoroethylated compounds of silicon, germanium and tin. The pronounced electron-withdrawing effect of the pentafluoroethyl group leads to a markedly increased Lewis acidity at the central atom which results in the stabilization of hypervalent complexes, anionic element(II) species as well as remarkable reactivities of element-element and element-hydrogen bonds. By addition to unsaturated C-C bonds or by reaction with organic halides as well as transition-metal complexes the molecules bearing a pentafluoroethyl-element group are readily accessible. Moreover, the utilization of pentafluoroethyl groups facilitates the formation of donor-stabilized germylenes and stannylenes. A series of such compounds serves as suitable pentafluoroethylation reagents. Conversely to the well-studied trifluoromethyl derivatives these compounds frequently exhibit a higher thermostability, which allows a more convenient handling.

The Dynamic Equilibrium of Hexakis(pentafluoroethyl)distannane Adducts [XSn(C2 F5 )3 {Sn(C2 F5 )3 }]- (X=Cl, Br, I, Sn(C2 F5 )3 )

The tin-tin bond cleavage of hexaorganodistannanes by nucleophiles is a long-known reaction and widely used for stannate formation or stannyl group transfer. Herein, we detail our experiments to provide analytical evidence for the existence of the reasonably stable anionic complexes [XSn(C₂ F₅ )₃ {Sn(C₂ F₅ )₃ }]^- (X=Cl, Br, I, Sn(C₂ F₅ )₃ ) derived from hexakis(pentafluoroethyl)distannane. NMR investigations at low temperature lend further mechanistic insights. Thus, by detection of the imposing ion [Sn(C₂ F₅ )₃ {Sn(C₂ F₅ )₃ }₂ ]^- , one can surmise that the chemistry of Sn₂ (C₂ F₅ )₆ has more in common with the isolobal iodine than with classical distannanes.