Nickel-Catalyzed Stereoselective Alkenylation of Ketones Mediated by Hydrazine

PPh3-Promoted Direct Deoxygenation of Epoxides to Alkenes

Deoxygenation of epoxides into alkenes is one of the most important strategies in organic synthesis, biomass conversions, and medicinal chemistry. Although metal-catalyzed direct deoxygenation provides one of the most commonly encountered protocols for the conversion of epoxides to alkenes, the requirement of expensive catalysts and extra reductants has largely limited their universal applicability. Herein, we report an efficient PPh3-promoted metal-free strategy for deoxygenation of epoxides to generate alkene derivatives. The success of deoxyalkenylation of epoxides bearing a wide range of functional groups to give terminal, 1,1-disubstituted, and 1,2-disubstituted alkenes manifests the powerfulness and versatility of this strategy. Moreover, gram-scale synthesis with excellent yield and modification of biologically active molecules exemplifies its generality and practicability.

Acetone Serving as a Solvent and Interaction Partner Promotes the Direct Olefination of N-Tosylhydrazones under Visible Light

The photochemistry of noncovalent interactions to promote organic transformations is an emerging approach to providing fresh opportunities in synthetic chemistry. Generally, the external substance is necessary to add as an interaction partner, thereby sacrificing the atom economy of the reaction. Herein, we describe a catalyst-free and noncovalent interaction-mediated strategy to access the olefination of N-tosylhydrazones using acetone as a solvent and an interaction partner. This protocol also features broad substrate scope, excellent functional group compatibility, and mild reaction conditions without transition metals. Moreover, the gram-scale synthesis of olefins and the generation of pharmaceutical intermediates highlighted its practical applicability. Lastly, mechanistic studies indicate that the reaction was initiated via noncovalent interactions between acetone and N-tosylhydrazone anion, which is also supported by density functional theory calculations.

Triflic Acid/Silane Promoted Deoxygenative Transformation of Ketones via Carbocations

Deoxygenative transformation of ketones into value-added products often suffers from precious-metal-based catalysts or complicated operational conditions. Triflic acid and silane serve as a cooperative reductant to transform ketones via carbocations that undergo β-H elimination much faster than hydride transfer from silane to produce alkenes with high selectivity. Alternatively, the presence of indoles would incept the protonated ketones to generate carbocations, allowing access to Csp2-Csp3 bond formation with high reactivity and selectivity in "one pot".

HOME-Chemistry: hydrazone as organo-metallic equivalent

The modern synthetic chemistry heavily relies on the use of stoichiometric organometallic reagents to react with various electrophiles. The dependence on stoichiometric quantities of metals and often organic halides as precursors, in turn both produces copious amounts of metal halide wastes as well as leads to concerns on future metal sustainability. Inspired by the classical Wolff-Kishner reduction, our lab has recently developed a general strategy of HOME-Chemistry , directly using naturally abundant alcohols/aldehydes and ketones as feedstocks with the releasing of innocuous water and nitrogen gas. These reactions include 1,2-carbonyl/imine addition, conjugate addition, carboxylation, olefination, cross-coupling arylation/allylation, alkylation, hydroalkylation and C-heteroatom formations. This article provides a brief summary on this chemistry.