247155-24-4Relevant academic research and scientific papers
Reactions of HDDA-Derived Benzynes with Sulfides: Mechanism, Modes, and Three-Component Reactions
Chen, Junhua,Palani, Vignesh,Hoye, Thomas R.
supporting information, p. 4318 - 4321 (2016/05/09)
We report here reactions of alkyl sulfides with benzynes thermally generated by the hexadehydro-Diels-Alder (HDDA) cycloisomerization. The initially produced 1,3-betaine (o-sulfonium/aryl carbanion) undergoes intramolecular proton transfer to generate a more stable S-aryl sulfur ylide. This can react in various manners, including engaging weak acids (HA) in the reaction medium. This can produce transient ion pairs ArSR2+A- that proceed to the products ArSR + RA. When cyclic sulfides are used, A- opens the ring and is incorporated into the product, an outcome that constitutes a versatile, three-component coupling process.
Bifunctional Br?nsted Base Catalyzes Direct Asymmetric Aldol Reaction of α-Keto Amides
Echave, Haizea,López, Rosa,Palomo, Claudio
supporting information, p. 3364 - 3368 (2016/03/22)
The first enantioselective direct cross-aldol reaction of α-keto amides with aldehydes, mediated by a bifunctional ureidopeptide-based Br?nsted base catalyst, is described. The appropriate combination of a tertiary amine base and an aminal, and urea hydro
Formal synthesis of (-)-cephalotaxine based on a tandem hydroamination/semipinacol rearrangement reaction
Zhang, Qing-Wei,Xiang, Kai,Tu, Yong-Qiang,Zhang, Shu-Yu,Zhang, Xiao-Ming,Zhao, Yu-Ming,Zhang, Tian-Cai
supporting information; experimental part, p. 894 - 898 (2012/07/13)
Catalytic asymmetric formal synthesis of (-)-cephalotaxine has been accomplished based on an efficient tandem intramolecular hydroamination/ asymmetric semipinacol rearrangement reaction catalyzed by chiral silver phosphate. During the course of the study it was observed that an advanced intermediate could be obtained in enantiopure form by enantiomer separation on silica gel.
Formamides derived from N-methyl amino acids serve as new chiral organocatalysts in the enantioselective reduction of aromatic ketimines with trichlorosilane
Malkov, Andrei V.,Ston?ius, Sigitas,MacDougall, Kenneth N.,Mariani, Andrea,McGeoch, Grant D.,Ko?ovsky, Pavel
, p. 264 - 284 (2007/10/03)
Asymmetric reduction of N-aryl ketimines 1a-k, 43, and 45 with trichlorosilane can be catalyzed by new N-methyl l-amino acid-derived Lewis-basic organocatalysts, such as the valine-derived bisamide 3d (10 mol%), in toluene at room temperature with high enantioselectivity (≤92% ee). The structure-reactivity investigation shows that the product configuration is controlled by the nature of the side chain of the catalyst scaffold (e.g., i-Pr vs Me, as in 3d and 6e), so that catalysts of the same absolute configuration may induce the formation of the opposite enantiomers of the product. Arene-arene interactions between the catalyst and the incoming imine appear to be the prerequisite for asymmetric induction. This metal-free, organocatalytic protocol is competitive with the traditional, metal-catalyzed methodology.
Syntheses of seven-membered rings: Ruthenium-catalyzed intramolecular [5+2] cycloadditions
Trost, Barry M.,Shen, Hong C.,Horne, Daniel B.,Toste, F. Dean,Steinmetz, Bernhard G.,Koradin, Christopher
, p. 2577 - 2590 (2007/10/03)
The Ru-catalyzed intramolecular [5+2] cycloaddition of cyclopropylenynes is investigated with respect to the regio- and diastereoselectivity as well as the functional group compatibility of the reaction. Evidence for the mechanism as occurring through a ruthenacyclopentene intermediate is elucidated from 1) the study of the diastereoselectivity of the cycloaddition; 2) the effect of variation of substituents on the regioselectivity of cyclopropyl bond cleavage in 1,2-trans- and 1,2-cis-disubstituted cyclopropanes and 3) examples that clearly do not involve ruthenacyclohexene as intermediates as products still incorporate the cyclo propyl moiety. The scope and limitations of the Ru-catalyzed cycloaddition are discussed and compared with the Rh-catalyzed reaction. The potential power of this methodology towards natural product total synthesis is demonstrated by the formation of several polycyclic systems with the chosen reaction conditions and readily available cyclopropylenyne substrates.
The Synthesis and Chemoselective Reactivity of 3-Aminocyclopentadienones
Rainier, Jon D.,Imbriglio, Jason E.
, p. 7272 - 7276 (2007/10/03)
Iron and cobalt complexes of 3-aminocyclopentadienones have been synthesized from the [2 + 2 + 1] cycloadditions of nitrogen acetylenes and pendant alkynes. Following decomplexation, the resulting 3-aminocyclopentadienones have been subjected to chemo- and regioselective cycloadditions with dienophiles and heterodienes.
A regioselective Ru-catalyzed alkene-alkyne coupling
Trost, Barry M.,Machacek, Michelle,Schnaderbeck, Matthew J.
, p. 1761 - 1764 (2007/10/03)
(matrix presented) The reaction of silylalkynes and terminal alkenes proceeds with complete control of regioselectivity by the silyl substituent to give geometrically defined vinylsilanes. Since terminal alkynes normally give mixtures, protodesilylation o
