ABSTRACT
A multicomponent cyclocondensation reaction between 2-aminoanthracene, aromatic aldehydes, and 5-α-cholestan-3-one has been used to synthesize model asphaltene compounds. The active catalyst for this reaction has been identified as hydriodic acid, which is formed in situ from the reaction of iodine with water, while iodine is not a catalyst under anhydrous conditions. The products, which contain a tetrahydro[4]helicene moiety, are optically active, and the stereochemical characteristics have been examined by VT-NMR and VT-CD spectroscopies, as well as X-ray crystallography.
Subject(s)
Acids/chemistry , Iodine Compounds/chemistry , Naphthoquinones/chemistry , Polycyclic Aromatic Hydrocarbons/chemistry , Steroids/chemistry , Aldehydes/chemistry , Anthracenes/chemistry , Catalysis , Crystallography, X-Ray , Models, Molecular , Molecular Conformation , Molecular StructureABSTRACT
The catalytic intermediate trans-[Ru((R)-BINAP)(H)2((R,R)-dpen)] (1) reacted on mixing with acetophenone in THF at -80 degrees C under approximately 2 atm H2 to generate the alkoxide trans-Ru((R)-BINAP)(H)((Ph)(Me)CHO)((R,R)-dpen) (6). Contrary to expectations, free Ru-amide and 1-phenylethanol were not the immediate products of this addition reaction. The addition reaction was reversible in THF. 2-Propanol prevents racemization of the alcohol product in THF solvent.
ABSTRACT
The dihydrogen compound trans-[Ru((R)-BINAP)(H)(eta2-H2)((R,R)-dpen)]+ (2', BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl, dpen = 1,2-diphenylethylenediamine) is a proposed intermediate in asymmetric ketone hydrogenations. It quickly reacts at -80 degrees C with 1 equiv of the base KOtBu in 2-PrOH-d8/CH2Cl2-d2 under H2 to generate trans-Ru((R)-BINAP)(H)(2-PrO)((R,R)-dpen) (4). The alkoxide 4 does not react with H2 after hours under ambient conditions. Addition of 1 equiv of KOtBu to 4 produces a hydrogen bonded species 10 that reacts readily with H2 at -80 degrees C to generate the dihydride catalytic intermediate trans-[Ru((R)-BINAP)(H)2((R,R)-dpen)] (3'). Addition of 1 equiv of ((CH3)3Si)2NK to the alkoxide 4 produces the amide catalytic intermediate 5. Compound 5 reacts reversibly with H2 to generate 3'.
ABSTRACT
The compound fac-[Ru((R)-BINAP)(H)(2-PrOH)3]+ (6) (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) reacts with (R,R)-dpen (dpen = 1,2-diphenylethylenediamine) under H2 at -60 degrees C in 2-PrOH-d8/CD2Cl2 to generate the cationic dihydrogen putative intermediate trans-[Ru((R)-BINAP)(H)(eta2-H2)((R,R)-dpen)]+ (2') without H-D exchange between the hydrogen ligands and the solvent. A 1H NMR study concludes that the dihydrogen ligand in 2' does not protonate 2-PrOH to a catalytically significant extent, and that 2' requires an added base or hydride source to be an active catalyst.
