Gregory H. P. Roos

Synthetic potential of the tertiary-amine-catalysed reaction of activated vinyl carbanions with aldehydes

Catalyse par le diaza-1,4bicyclo [2.2.2] octane, la quinuclidine et ses derives, la quinine

TEMPERATURE AND ULTRASOUND RATE ENHANCEMENT IN THE BAYLIS-HILLMAN REACTION

Abstract Synthetically useful increases in reaction rate are achieved in the DABCO (1,4-diazabicyclo [2. 2. 2] octane) catalysed coupling of aldehydes with methyl acrylate by the application of ultrasound.

Synthesis of 3-Hydroxy-2-Methylene Carbonyl Compounds - Effect of Catalyst and Substrate on Reaction Rate

Abstract 3-Hydroxyquinuclidine enhances the rate of formation of the title compounds whereas the acetylated derivative is a poor catalyst. A comparative study shows that methyl vinyl ketone is more reactive than methyl acrylate in the Baylis-Hillman reaction.

A Facile Synthesis of Homochiral Rh(II) Carboxylates

Abstract Homochiral Rh(II) carboxylates, Rh2(OCOR)4, are readily prepared in good yield by reaction of carboxylic acids with the Rh(II) carbonato species, Na4Rh2(CO3)4.

Improved enantioselection for chiral dirhodium(II) carboxamide-catalysed carbon-hydrogen insertion reactions of tertiary alkyl diazoacetates

Abstract Enantiocontrol in Cue5f8H insertion reactions of 3° alkyl diazoacetates, which is highly dependent on the catalyst ligand, is greatly enhanced with the use of dirhodium(II) tetrakis[methyl 1-acetylimidazolidin-2-one-4(S)-carboxylate], Rh 2 (4S-MACIM) 4 .

A Facile, Efficient Route to Methyl α-Hydroxymethylacrylate and Methyl α-Halomethylacrylates

Abstract DABCO-catalysed coupling of formaldehyde and methyl acrylate provides the title hydroxy compound. Treatment with HBr conveniently affords the key synthetic intermediate methyl α-bromomethylacrylate in good overall yield.

Stereoselective Addition of Methyl Acrylate to α-Amino Aldehydes

Abstract Variously N-protected α-aminoaldehydes exhibit reasonable diastereoselectivity in the Baylis-Hillman coupling1 with methyl acrylate to provide either primarily syn or anti α-methylene-β-hydroxy-γ-amino esters.

Stereoselective Synthesis of α-Methylene-β-Hydroxy-γ-Alkoxy Esters and Ketones

Abstract The amine catalysed aldol-type addition of vinylcarbonyl units to α-alkoxy aldehydes proceeds with reasonable diastereoface selectivity to afford the title compounds in good yield.

(4,0)-Dirhodium(II) tetrakis[methyl 1-acetyl-2-oxoimidazolidine-4(S)-carboxylate]. Implications for the mechanism of ligand exchange reactions

Abstract The preparation and structural characterization of an elusive geometrical isomer of dirhodium(II) tetrakis[methyl 1-acetyl-2-oxoimidazolidine-4(S)-carboxylate], Rh2(4S-MACIM)4, has been achieved. The imidazolidinone ligands are arrayed around the dirhodium(II) core with four nitrogen donor atoms bound to one rhodium and four oxygens bound to the other (4,0). The crystal structure of this compound has been determined to be that of (4,0)-Rh2(4S-MACIM)4(CH3CN)2d(CH3CN): space group P2(in1) with cell constants a = 11.518(4), b = 16.851(2), c = 11.573(3) A , V = 2155.4(6) A 3 , Z = 2,R = 0.0295, Rhue5f8Rh distance = 2.4547(6) A . Prepared by ligand substitution on Rh2(OAc)4, (4,0)-Rh2(4s-MACIM)4 was isolated in 25% yield, but this compound isomerizes to its (2,2-cis)- and (3,1)-isomers under the reaction conditions. Racemic products were obtained from catalytic uses of (4,0)-Rh2(4S-MACIM)4 in diazo decomposition reactions.

A novel imidazolidin-2-one auxiliary for a highly stereoselective aldol route to β-hydroxyesters.

Abstract Enantiomerically pure syn -aldols are obtained from the boron enolate of (4R,5S)-1,5-dimethyl-4-cyclohexyl-3- propanoyl imidazolidin-2-one. Cleavage of the auxiliary affords the homochiral title esters in good yield.