618905-87-6Relevant articles and documents
Crucial role of β-elimination in determining regio- and chemoselectivity of the rhodium-catalyzed hydroformylation of N -allylpyrroles: A new approach to 5,6-dihydroindolizines
Settambolo, Roberta
experimental part, p. 2915 - 2921 (2010/10/21)
Rhodium-catalyzed hydroformylation of the chiral (S)-3-alkyl-3-pyrrol-1- ylprop-1-enes at 100 atmospheres total pressure and 25C led to the preferential formation of the branched 3-alkyl-2-methyl-3-pyrrol-1-ylpropanals. At 30 atmospheres and 125°C, the linear 4-alkyl-4-pyrrol-1-ylbutanals were obtained: these aldehydes are not the final products, but evolve into more stable 5,6-dihydroindolizines, with the same optical purity as the starting olefins, via a domino cyclization-dehydration process. According to the generally accepted mechanism for rhodium-catalyzed hydroformylation, the regioselectivity, and then the final chemoselectivity, can be rationalized by taking into account that while at room temperature no -elimination occurs, at high temperature the -elimination involves the branched rhodium-alkyl intermediate only.
A new class of optically active pyrrole derivatives: (3R)-3-(pyrrol-1-yl)alk-1-enes from D-α-aminoacids
Settambolo, Roberta,Guazzelli, Giuditta,Mengali, Lucia,Mandoli, Alessandro,Lazzaroni, Raffaello
, p. 2491 - 2493 (2007/10/03)
(3R)-3-(Pyrrol-1-yl)but-1-ene 4a, (3R)-4-methyl-3-(pyrrol-1-yl)pent-1-ene 4b, (3R)-3-(pyrrol-1-yl)hex-1-ene 4c in high enantiomeric excess (>92%) were prepared starting from D-α-amino acids. The crucial steps in the synthesis, reduction (DIBAH) of the corresponding pyrrolylesters to the corresponding pyrrolylaldehydes followed by Wittig olefination proceeded without compromising the stereochemical integrity.
Influence of the reaction temperature on the regioselectivity in the rhodium-catalyzed hydroformylation of vinylpyrroles
Caiazzo, Aldo,Settambolo, Roberta,Uccello-Barretta, Gloria,Lazzaroni, Raffaello
, p. 279 - 284 (2007/10/03)
The influence of the temperature on the regioselectivity in the hydroformylation of the vinylpyrrole isomers and of the corresponding N-tosylated substrates has been investigated in the range 20-100°C, in the presence of Rh4(CO)12. At all the temperatures the branched aldehyde was prevailing with respect to the linear isomer for all the substrates ( α-regioselectivity). With increasing temperature, an increase of the linear aldehyde was observed to a different extent in dependence on the substrate nature. 2H NMR investigation of the crude reaction mixture recovered from deuterioformylation of 3-vinylpyrrole at partial substrate conversion points out that the observed depression of the α-regioselectivity with increasing temperature must be connected to a β-hydride elimination process occurring for the branched alkyl-rhodium intermediates but not for the linear ones.
High α-regioselectivity in the rhodium-catalyzed hydroformylation of vinylpyrroles
Settambolo, Roberta,Caiazzo, Aldo,Lazzaroni, Raffaello
, p. 337 - 338 (2007/10/02)
The Rh4(CO)12-catalyzed hydroformylation at low temperature (40°C) of the 1-, 2- and 3-vinylpyrrole gives the corresponding branched aldehydes 2-(1-pyrrolyl)propanal, 2-(2-pyrrolyl)propanal and 2-(3-pyrrolyl)propanal with high α-regioselectivity.
Synthesis and Stereoselective Reactions of 2-(Pyrrol-1-yl)alkanals and 2-(pyrrol-1-yl)alkan-1-ones
Kashima, Choji,Maruyama, Tatsuya,Fujioka, Yoko,Harada, Kazuo
, p. 1041 - 1046 (2007/10/02)
2-(2,5-Dimethylpyrrol-1-yl)alkanals, 2-(pyrrol-1-yl)alkanals, and 2-(2,5-dimethylpyrrol-1-yl)alkan-1-ones were prepared.The reactions of these compounds with Grignard and hydride reagents proceeded stereoselectively to give the corresponding 2-(pyrrol-1-yl)alcohols, which were converted into 2-aminoalcohols, such as norephedrine and ephedrine, by cleavage of the pyrrole ring.
