153495-48-8Relevant academic research and scientific papers
trans-hydroalumination/alkylation: One-pot synthesis of trisubstituted allylic alcohols
Langille, Neil F.,Jamison, Timothy F.
, p. 3761 - 3764 (2006)
Described herein is a method of stereoselective synthesis of trisubstituted allylic alcohols by alkylation of alkenyl alanates, formed in situ through treatment of propargyl alcohols with Vitride (Red-Al). This technique represents the first of its kind to feature a trans-hydrometalation, and is particularly effective for the formation of 1,4-dienes. Applications involving primary, secondary, and tertiary alcohols are discussed, as well as limitations regarding both alkyne and electrophile components.
Primary and secondary allyltitanium(IV) reagents in aldehyde allylation II: Application to an enantioselective preparation of a C1-C7 fragment of spiramycin
Razon, Patrick,N'Zoutani, Marie-Ange,Dhulut, Sylvie,Bezzenine-Lafollee, Sophie,Pancrazi, Ange,Ardisson, Janick
, p. 109 - 121 (2007/10/03)
A synthetic approach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe aldehyde allylation. This reaction was carried out between an optically pure aldehyde 32 and a (±)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions, the anti-Cram compound 35 was obtained in an 80:20 mixture, with the Cram isomer 34, in 81% yield. Employing the optically pure (S)-γ-alkoxy allyl (diisopropyl)carbamate 36, the corresponding (R)-γ-alkoxy allyltitanium (R)-'Ti'-III was generated under n-BuLi·TMEDA/Ti(Oi-Pr)4 conditions, that reacted with aldehyde 32 in double stereodifferentiation to deliver the expected Cram compound 40 in 80% yield (95% de). This latter corresponded to the C1-C7 fragment of spiramycin.
Bronsted acid-promoted cyclizations of 1-siloxy-1,5-diynes
Sun, Jianwei,Kozmin, Sergey A.
, p. 13512 - 13513 (2007/10/03)
We have developed the first HNTf2-promoted 5-endo-dig cyclizations of 1-siloxy-1,5-diynes, which proceed with concomitant formation of C-Hal bonds as a result of halide abstraction from a halocarbon by the intermediate alkenyl cation. This process is enabled by a chemoselective activation of the more electron-rich siloxy alkyne moiety of the diyne cyclization precursor and represents an efficient and highly diastereoselective method for assembly of a range of β-halo enones. Copyright
Vinyl sulfoxides as stereochemical controllers in intermolecular Pauson-Khand reactions: Applications to the enantioselective synthesis of natural cyclopentanoids
Rodriguez Rivero, Marta,Alonso, Ines,Carretero, Juan C.
, p. 5443 - 5459 (2007/10/03)
The use of sulfoxides as chiral auxiliaries in asymmetric intermolecular Pauson-Khand reactions is described. After screening a wide variety of substituents on the sulfur atom in α,β-unsaturated sulfoxides, the readily available o-(N,N-dimethylamino)phenyl vinyl sulfoxide (1i) has proved to be highly reactive with substituted terminal alkynes under N-oxide-promoted conditions (CH3CN, 0°C). In addition, these Pauson-Khand reactions occurred with complete regioselectivity and very high diastereoselectivity (de = 86→96%, (S,RS) diastereomer). Experimental studies suggest that the high reactivity exhibited by the vinyl sulfoxide 1i relies on the ability of the amine group to act as a soft ligand on the alkyne dicobalt complex prior to the generation of the cobaltacycle intermediate. On the other hand, both theoretical and experimental studies show that the high stereoselectivity of the process is due to the easy thermodynamic epimerization at the C5 center in the resulting 5-sulfinyl-2- cyclopentenone adducts. When it is taken into account that the known asymmetric intermolecular Pauson-Khand reactions are limited to the use of highly reactive bicyclic alkenes, mainly norbornene and norbornadiene, this novel procedure constitutes the first asymmetric version with unstrained acyclic alkenes. As a demonstration of the synthetic interest of this sulfoxide-based methodology in the enantioselective preparation of stereochemically complex cyclopentanoids, we have developed very short and efficient syntheses of the antibiotic (-)-pentenomycin I and the (-)-aminocyclopentitol moiety of a hopane triterpenoid.
