Roberta Settambolo

INFLUENCE OF THE REACTION TEMPERATURE ON THE REGIOSELECTIVITY IN THE RHODIUM-CATALYZED HYDROFORMYLATION OF VINYLPYRROLES

Abstract 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 Rh 4 (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. 2 H 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.

Synthesis of (-)-Indolizidine 167B based on domino hydroformylation/cyclization reactions

The synthesis of (-)-Indolizidine 167B has been achieved from optically active (R)-3-(pyrrol-1-yl)hex-1-ene. The key step is a highly regioselective hydroformylation reaction and a one-pot intramolecular cyclization providing a general approach to the indolizine nucleus.

Synthesis of 4‐(Indol‐1‐yl)butanals via Rhodium‐Catalyzed Hydroformylation of 1‐Allylindoles

Abstract The rhodium‐catalyzed hydroformylation of new 1‐(β‐methallyl) indoles 1a–e carried out with Rh4 (CO)12 as the catalyst precursor, at 100 atm total pressure and 100°C, produces the 4-(indol‐1‐yl)‐3‐methylbutanals 2a–e as the sole products in high yields. The synthesized 4‐indolylbutanals are stable under the adopted conditions and are isolated and characterized here for the first time. The preparation of the starting 1‐allylindoles is described too.

Rhodium-Catalyzed Hydroformylation in Fused Azapolycycles Synthesis

N-Heterocycles, including fused ones, have proven to be an important class of compounds since they possess biological and pharmacological activities themselves and serve as valuable intermediates for synthetic drug discovery. My interest in the synthesis of these compounds stems from studies dealing with the hydroformylation (oxo) of olefins. The dihydroindolizines and benzofused ones are easily generated via rhodium-catalyzed hydroformylation of N-allylpyrroles and indoles: the butanal intermediate undergoes an intramolecular cyclodehydration giving the final polycyclic compound. This chapter reports my results in the area of the conversions of oxo aldehydes with additional C,C-bond-forming reactions together with relevant work from other laboratories on additional C,N-bond-forming reactions, encountered in the field of Azapolycycles synthesis over the last 5 years or so. The intramolecular sequences for polycylization will be especially emphasized using rhodium complexes to effect these transformations, under both conventional and microwave heating.