Reaction of Diazo Compounds with Difluorocarbene: An Efficient Approach towards 1,1-Difluoroolefins

Direct gem-Difluoroalkenylation of X-H Bonds with Trifluoromethyl Ketone N-Triftosylhydrazones for Synthesis of Tetrasubstituted Heteroatomic gem-Difluoroalkenes

The direct gem-difluoroalkenylation of X-H bonds represents the most straightforward approach to access heteroatomic gem-difluoroalkenes that, as the isostere of the carbonyl group, have great potency in drug discovery. However, the construction of tetrasubstituted heteroatomic gem-difluoroalkenes by this strategy is still an unsolved problem. Here, we report the first direct X-H bond gem-difluoroalkenylation of amines and alcohols with trifluoromethyl ketone N-triftosylhydrazones under silver (for (hetero)aryl hydrazones) or rhodium (for alkyl hydrazones), thereby providing a most powerful method for the synthesis of tetrasubstituted heteroatomic gem-difluoroalkenes. This method features a broad substrate scope, high product yield, excellent functional group tolerance, and operational simplicity (open air conditions). Moreover, the site-specific replacement of the carbonyl group with a gem-difluorovinyl ether bioisostere in drug Trimebutine and the post-modification of bioactive molecules demonstrates potential use in medicinal research. Finally, the reaction mechanism was investigated by combining experiments and DFT calculations, and disclosed that the key step of HF elimination occurred via five-membered ring transition state, and the difference in the electrophilicity of Ag- and Rh-carbenes as well as the multiple intermolecular interactions rendered the effectiveness of Rh catalyst selectively for alkyl hydrazones.

Water-promoted regio-selective trifluoromethylation of vinyl conjugated diazoacetates

An efficient trifluoromethylation reaction of vinyldiazoacetates under mild reaction conditions was depicted.

Electroreductive Cross-Coupling of Trifluoromethyl Alkenes and Redox Active Esters for the Synthesis of Gem-Difluoroalkenes

An electroreductive access to gem-difluoroalkenes has been developed through the decarboxylative/defluorinative coupling of N-hydroxyphtalimides esters and α-trifluoromethyl alkenes. The electrolysis is performed under very simple reaction conditions in an undivided cell using cheap carbon graphite electrodes. This metal-free transformation features broad scope with good to excellent yields. Tertiary, secondary as well as primary alkyl radicals could be easily introduced. α-aminoacids L-aspartic and L-glutamic acid-derived redox active esters were good reactive partners furnishing potentially relevant gem-difluoroalkenes. In addition, it has been demonstrated that our electrosynthetic approach toward the synthesis of gem-difluoroalkenes could use an easily prepared Kratitsky salt as alkyl radical precursor via a deaminative/defluorinative carbofunctionalization of trifluoromethylstyrene.

Synthesis of gem-Difluoro Olefins through C-H Functionalization and β-fluoride Elimination Reactions

A palladium catalyzed C−H functionalization and consecutive β‐fluoride elimination reaction between indole heterocycles and fluorinated diazoalkanes is reported. This approach provides for the first time a facile method for the rapid synthesis of gem‐difluoro olefins using fluorinated diazoalkanes under mild reaction conditions. Cyclopropanation products were obtained when N‐arylated rather than N‐alkylated indoles were applied in this reaction. Mechanistic studies reveal the importance of the β‐fluoride elimination step in this transformation. This method presents a new concept for the simple and direct transfer of a 1‐aryl‐(2,2‐difluorovinyl) group to access gem‐difluoro olefins.

A Catalytic Cross-Olefination of Diazo Compounds with Sulfoxonium Ylides

A ruthenium‐catalysed cross‐olefination of diazo compounds and sulfoxonium ylides is presented. Our reaction design exploits the intrinsic difference in reactivity of diazo compounds and sulfoxonium ylides as both carbene precursors and nucleophiles, which results in a highly selective reaction.

Radical-carbene coupling reaction: Mn-catalyzed synthesis of indoles from aromatic amines and diazo compounds

An unprecedented coupling reaction between aromatic amines and diazo compounds was well developed, which afforded a bridge connecting between radical chemistry and metal carbene chemistry. This Mn-catalyzed tandem reaction also provided a fundamentally different and practical approach to the indole skeleton under mild conditions.

Highly Stereoselective Gold-Catalyzed Coupling of Diazo Reagents and Fluorinated Enol Silyl Ethers to Tetrasubstituted Alkenes

We report a highly stereoselective synthesis of all-carbon or fluorinated tetrasubstituted alkenes from diazo reagents and fluorinated enol silyl ethers, using C-F bond as a synthetic handle. Cationic Au^I catalysis plays a key role in this reaction. Remarkable fluorine effects on the reactivity and selectivity was also observed.