Magnesium Sulfate Catalyzed Intermolecular Wittig Reaction of Dialkyl 2-(1-acetyl-2-oxopropyl)-3-(triphenylphosphoranylidene) Succinates with Ninhydrin in Solvent-Free Conditions

A facial one-pot stereoselective synthesis of dialkyl 3,3-diacetyl-3 a -hydroxy-8-oxo-2,3,3 a ,8-tetrahydrocyclopenta[ a ]indene-1,2-dicarboxylates in fairly high yields by the intermolecular Wittig reaction of dialkyl 2-(1-acetyl-2-oxopropyl)-3-(triphenylphosphoranylidene) succinates and ninhydrin in the presence of MgSO 4 in solvent-free conditions at 100°;C is reported.     

Synthesis of stable arsonium and sulfur ylides from perfluoroalkanesulfonyl diazocarbonyl compounds and their X-ray diffraction analysis

A series of stable fluorine-containing arsonium ylides and sulfur ylides were simply synthesized from perfluoroalkanesulfonyl diazocarbonyl compounds in the presence of rhodium catalyst. The ylide products are fairly stable due to the strong electron-withdrawing properties of perfluoroalkanesulfonyl group and carbonyl group. They are fully confirmed by spectral methods and the structures of 3ba and 3cd are also established by X-ray single crystal diffraction analysis. Several interesting features about the ylide structures and some weak fluorine interaction between them are described here.     

Selectivity Control of the Ligand Exchange at Carbon in α-Metallated Ylides as a Route to Ketenyl Anions**

α-Metallated ylides have recently been reported to undergo phosphine by CO exchange at the ylidic carbon atom to form isolable ketenyl anions. Systematic studies on the tosyl-substituted yldiides, R₃P=C(M)Ts (M=Li, Na, K), now reveal that carbonylation may lead to a competing metal salt (MTs) elimination. This side-reaction can be controlled by the choice of phosphine, metal cation, solvent and co-ligands, thus enabling the selective isolation of the ketenyl anion [Ts−CCO]M ( 2-M ). Complexation of 2-Na by crown ether or cryptand allowed structure elucidation of the first free ketenyl anion [Ts−CCO]⁻, which showed an almost linear Ts−C−C linkage indicative for a pronounced ynolate character. However, DFT studies support a high charge at the ketenyl carbon atom, which is reflected in the selective carbon-centered reactivity. Overall, the present study provides important information on the selectivity control of ketenyl anion formation which will be crucial for future applications.     

Generation of Aromatic N-Heterocyclic Radicals for Functionalization of Unactivated Alkenes

Nitrogen-centered radicals (NCRs) have been widely recognized as versatile synthetic intermediates for the construction of nitrogen containing molecules of high value. As such, there has been a long-standing interest in the field of organic synthesis to develop novel nitrogen-based radicals and explore their inherent reactivity. In this study, we present the generation of aromatic N-heterocyclic radicals and their application in a novel and diverse functionalization of unactivated alkenes. Bench-stable aromatic N-heterocyclic pyridinium salts were employed as crucial NCR precursors, which enabled the efficient conversion of various unactivated alkenes into medicinally relevant alkylated N-heterocyclic amines. This approach offers an unexplored retrosynthetic disconnection for the synthesis of related molecules that commonly possess therapeutic value. Furthermore, this platform can be extended to the synthesis of densely functionalized heterocyclic amines by utilizing disulfides and diethyl bromomalonate as radical quenchers. Mechanistic investigations indicate an energy transfer (EnT) pathway involving the formation of a transient aromatic N-heterocyclic radical, radical addition to unactivated alkenes, and subsequent generation of the amination product through either hydrogen atom transfer (HAT) or radical addition processes.     

(2‐Bromoethyl)sulfonium Trifluoromethanesulfonates in Stereoselective Annulation Reactions for the Formation of Fused Bicyclic Epoxides and Aziridines

A versatile and simple method is reported for the synthesis of bicyclic epoxide and aziridine? fused heterocycles (up to 98% yield, up to 96 : 4 er or up to 15 : 1 dr), using a tandem Michael addition/Johnson? Corey? Chaykovsky annulation approach. A new chiral (2‐bromoethyl)sulfonium reagent is described, based on an easily available chiral sulfide; it promotes or enhances stereoselectivity in the reaction.     

A Concise, metathesis based approach to construction of the lepadiformine/cylindricine tricyclic framework

A tandem dienyne metathesis based strategy has been developed for construction of the core tricyclic framework found in the lepadiformine and cylindricine alkaloids. 2-Pentenyl-2-ethynylpyrollidine acrylamide that serves as the starting material for the key ruthenium carbene catalyzed metathesis process is prepared by using a concise route starting with l-proline.