Fe(0)-mediated synthesis of tri- and tetra-substituted olefins from carbonyls: an environmentally friendly alternative to Cr(II)

Synthesis of Diarylamines via Nitrosonium-Initiated C-N Bond Formation

Electron-rich diarylamines, exemplified by anisole-derived amines, play pivotal roles in process chemistry, pharmaceuticals, and materials. In this study, homo-diarylamines were synthesized directly from the C-H activation of electron-rich arenes by sodium nitrate/trifluoroacetic acid and the successive treatment of iron powder. Mechanistic investigations reveal that nitrosoarene serves as the reaction intermediate, and the formation of the second C-N bond between the resulting nitrosoarene and electron-rich arene is catalyzed by the nitrosonium ion (NO+). Thus, hetero-diarylamines were synthesized using preformed nitrosoarenes and various electron-rich arenes. This reaction complements a range of cross-coupling reactions catalyzed by transition metal catalysts.

Cyclization of 5-alkynones with chromium alkylidene equivalents generated in situ from gem-dichromiomethanes

A rare example of cyclization with 5-alkynones, which possess non-polar alkynyl and less electrophilic polar keto carbonyl groups, was demonstrated. The key to promoting carbene/alkyne metathesis followed by alkylidenation with pendant C[double bond, length as m-dash]O double bonds was the Schrock-type nucleophilic reactivity of the generated chromium carbene equivalents from readily available diiodomethanes and CrCl₂ by simple heating.

Structural Characterization and Unique Catalytic Performance of Silyl-Group-Substituted Geminal Dichromiomethane Complexes Stabilized with a Diamine Ligand

Stabilization by a silyl group on the methylene carbon and a diamine ligand led to the isolation of gem-dichromiomethane species. X-ray crystallography confirmed the identity of the structure of this rare example of reactive gem-dimetalloalkane species. The isolated gem-dichromiomethane complex acted as a storable silylmethylidene carbene equivalent, with reactivity that could be changed dramatically upon addition of a Lewis acid (ZnCl₂) and a base (TMEDA) to promote both silylalkylidenation of polar aldehydes and silylcyclopropanation of nonpolar alkenes. Identification of a key reactive species also identified the catalytic version of these transformations and provided insights into the reaction mechanism. In contrast to Simmons-Smith cyclopropanation, the real reactive species for the current cyclopropanation was a chromiocarbene species, not a chromium carbenoid species.

Cascade synthesis of (E)-2-alkylidenecyclobutanols

A facile, one-pot reaction cascade condenses 1,1,1-trichloroalkanes with alpha,beta-unsaturated ketones to unexpectedly furnish moderate to good yields of (E)-2-alkylidenecyclobutanols.

Stereoselective synthesis of (Z)-alpha-halo-alpha,beta-unsaturated esters, and amides from aldehydes and trihaloesters or amides promoted by manganese

Preliminary results of a Mn-promoted sequential process directed toward the stereoselective synthesis of different (Z)-alpha-halo-alpha,beta-unsaturated compounds are described.