Organosilicon Reducing Reagents for Stereoselective Formations of Silyl Enol Ethers from α-Halo Carbonyl Compounds.

Salt-free stereoselective synthesis of silyl enol ethers was achieved by treating α-halo carbonyl compounds with 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine. In this reaction, easily removable trimethylsilyl halides and 2,3,5,6-tetramethylpyrazine were generated as the reaction byproducts. Due to the inertness of the reaction byproducts, we found a one-pot transformation of the in situ generated silyl enol ethers into various α-functionalized carbonyls by reaction with Togni-II reagent or aldehydes.

Mixed Ligated Tris(amidinate)dimolybdenum Complexes as Catalysts for Radical Addition of CCl to 1-Hexene: Leaving Ligand Lability Controls Catalyst Activity.

We synthesized a series of mixed ligated tris(amidinate)dimolybdenum complexes, namely, [Mo(DAniF)(L)] [DAniF = N,N'-di(p-anisyl)formamidinate; L = acetate (OAc; 1a), m-diphenylphosphino benzoate (m-PPhBz; 1b), nicotinate (Nico; 1c), benzoate (Bz; 1d), 3-furoate (3-Furo; 1e), isonicotinate (IsoNico; 1f), and trifluoromethanesulfonate (OTf; 1g)], which served as catalysts for radical addition of CCl to 1-hexene to give 1,1,1,3-tetrachloroheptane. These mixed ligated complexes 1a-g afforded the higher yield of the radical addition product than a homoleptic DAniF complex, [Mo(DAniF)] (2). Among them, complexes 1a and 1g gave the radical addition product quantitatively after 9 h with a short induction period.

Mixed-ligand complexes of paddlewheel dinuclear molybdenum as hydrodehalogenation catalysts for polyhaloalkanes.

We developed a hydrodehalogenation reaction of polyhaloalkanes catalyzed by paddlewheel dimolybdenum complexes in combination with 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene (MBTCD) as a non-toxic H-atom source as well as a salt-free reductant. A mixed-ligated dimolybdenum complex Mo(OAc)[CH(NAr)] (, Ar = 4-MeOCH) having two acetates and two amidinates exhibited high catalytic activity in the presence of BuNCl, in which [ BuN][Mo{CH(NAr)}Cl] (), derived by treating with ClSiMe and BuNCl, was generated as a catalytically-active species in the hydrodehalogenation. All reaction processes, oxidation and reduction of the dimolybdenum complex, were clarified by control experiments, and the oxidized product, [ BuN][Mo{CH(NAr)}Cl] (), was characterized by EPR and X-ray diffraction studies.