Reductive opening of 2-phenyl-1,3-dioxolanes by a naphthalene-catalysed lithiation: synthetic applications
摘要:
The reaction of 2-phenyl-1,3-dioxolanes 1a,b with an excess of lithium powder in the presence of a catalytic amount of naphthalene (4 mol %) in tetrahydrofuran at -40-degrees-C followed by successive reaction with an electrophile and final hydrolysis with water at the same temperature yields the corresponding monoprotected 1,2-diols 2aa-2bf. The same process but allowing to rise the temperature to 20-degrees-C before the hydrolysis affords alcohols 3aa-3bd. The use of 2,2-diphenyl-1,3-dioxolane 1d, under similar reaction conditions as for compounds 2, permits the isolation of 2,2-diphenylalcohols 11da-11dc, resulting from the reaction with two different electrophiles. A mechanistic rationalization for all processes is given.
Highly Efficient and Enantioselective α-Arylation of Cycloalkanones by Scandium-Catalyzed Diazoalkane-Carbonyl Homologation
作者:Jason Kingsbury、Victor Rendina、Hilan Kaplan
DOI:10.1055/s-0031-1289650
日期:2012.3
Functionalized α-tertiary and -quaternary 2-arylcycloalkanones are rapidly accessed by scandium(III) triflate-catalyzed diazoalkane-carbonyl homologations. Recent developments have allowed for carbon insertion reactions to be performed with catalyst loadings as low as 0.5 mol% on scales up to 5 mmol. Pairing readily available bis- and tris(oxazoline) based ligands with scandium triflate allows access to arylated medium ring carbocycles with enantioselectivities up to 98:2 er and >98% yield. The formal C-C insertion of aryldiazomethanes into unsubstituted cycloalkanones provides a single-step solution to the ongoing challenge of α-arylation.
Mg-promoted reduction of a mixture of aromaticketones (or imines) and aliphatic carbonyl compounds in N,N-dimethylformamide (DMF) brought about unique mixed pinacol type of cross coupling to give unsymmetrical vicinal diols (or amino alcohols) or α-hydroxyketones in good to moderate yields. The reaction may be initiated by electron transfer from magnesium metal to an aromatic carbonyl compound possessing a
Catalytic Diazoalkane-Carbonyl Homologation: Synthesis of 2,2-Diphenylcycloheptanone and Other Quaternary or Tertiary Arylalkanones and Spirocycles by Ring Expansion
作者:Jason S. Kingsbury
DOI:10.15227/orgsyn.098.0343
日期:——
Molecular Rearrangements. IV. The Pinacol Rearrangement of 1-Hydroxy-1-cyclohexylmethylphenylcarbinol<sup>1</sup>