Synthesis of monofluorinated C4-building blocks based on methallyl chloride

Selective Synthesis of Monofluorinated Compounds Applying Amine/HF Reagents

For nucleophilic monofluorination, amine/HF reagents such as Et3 N⋅3HF, Pyr⋅9HF (Olah's reagent) and similar combinations belong to the most frequently used fluoride sources, whereupon the selectivity of these reagents can be very different depending of its acidity, the nucleophilicity of the fluoride equivalent, and the structure of the particular substrate. These reagents can be used safely in ordinary chemistry laboratories for nucleophilic substitution reactions by fluoride at sp3 -hybridized carbon centers. For ring opening reactions of epoxides, the regio- and stereoselectivity is very much depending of the nature of the epoxide and the acidity of the HF reagent favoring either SN 1 or SN 2 type reactions. Similarly, the outcome of halofluorination and similar reactions with sulfur or seleno electrophiles can be controlled by the particular combination of the electrophile and the fluoride source. Examples for the application of these reaction types for the synthesis of fluorine-containing analogues of natural products or biologically relevant compounds are in the focus of this personal account.

Intramolecular Alkene Fluoroarylation of Phenolic Ethers Enabled by Electrochemically Generated Iodane

The 3-substituted chromane core is found in several bioactive natural products. Herein, we describe a route to 3-fluorinated chromanes from allylic phenol ethers. Our external oxidant-free approach takes advantage of an electrochemical generation of a hypervalent iodine species, difluoro-λ³-tolyl iodane, which mediates the alkene fluoroarylation. High yields and selectivity for this transformation are achieved for electron poor substrates. The redox chemistry has been characterized for the electrochemical generation of the iodane in the presence of fluoride, and insights into the mechanism are given. The transformation has been demonstrated on gram scales, which indicates the potential broader utility of the process.

Enantioselective Synthesis of 3-Fluorochromanes via Iodine(I)/Iodine(III) Catalysis

The chromane nucleus is common to a plenum of bioactive small molecules where it is frequently oxidized at position 3. Motivated by the importance of this position in conferring efficacy, and the prominence of bioisosterism in drug discovery, an iodine(I)/iodine(III) catalysis strategy to access enantioenriched 3-fluorochromanes is disclosed (up to 7:93 e.r.). In situ generation of ArIF2 enables the direct fluorocyclization of allyl phenyl ethers to generate novel scaffolds that manifest the stereoelectronic gauche effect. Mechanistic interrogation using deuterated probes confirms a stereospecific process consistent with a type IIinv pathway.

Highly regio- and stereoselective trans-iodofluorination of ynamides enabling the synthesis of (E)-α-fluoro-β-iodoenamides

A highly regio- and stereoselective trans-iodofluorination reaction of ynamides with NIS and Et₃N·3HF has been achieved, affording (E)-α-fluoro-β-iodoenamides in moderate to good yields. The reaction proceeds under mild reaction conditions and exhibits good functional group compatibility.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Iodoarene-catalyzed fluorination and aminofluorination by an Ar-I/HF·pyridine/mCPBA system

We have developed the iodoarene-catalyzed fluorination of carbonyl compounds and intramolecular aminofluorination of ω-amino-alkenes using HF/mCPBA.

Synthesis of a fluorinated analogue of anticancer active ether lipids

The synthesis of racemic 2'-(trimethylammonium)ethyl-3-hexadecyloxy-2-fluoro-2-(methoxymethyl)prop-1-yl-phosphate (6), a fluorinated analogue of an anticancer active ether lipid 5 was realized with 3% overall yield in a nine-step synthesis starting from 2-methylene-1,3-propanediol (7) using a bromofluorination as the key step. Both enantiomers of the precursor 8 of the ether lipid 6 were synthesized by lipase-catalyzed desymmetrization of the diacetate 17, either by hydrolysis (83% ee) or by lipase-catalyzed acetylation of the diol 22 (82% ee). The antitumor activity of 6 has been found in an in vivo model of the methylcholanthrene-induced fibrosarcoma of mice.