RESUMEN
Cascade aza-Piancatelli reaction and [3+3]/[4+2] cycloaddition reactions are carried out using the ideality principles of pot, atom, and step economy (PASE) synthesis. The reaction resulted in generation of octahydro-4H-cyclopenta[b]pyridin-6-one scaffolds. Moreover, octahydro-5,7a-epoxycyclopenta[cd]isoindol-4-one frameworks of gracilamine alkaloid and a novel decahydro-1H-dicyclopenta[cd,hi]isoindol-6-one were also realized in good yields with excellent regio- and diastereo-selectivities.
RESUMEN
A new class of chiral 2,2'-bipyridine ligands, SBpy, featuring minimized short-range steric hindrance and structural tunability was rationally designed and developed, and the effectiveness was demonstrated in the first highly enantioselective Ni-catalyzed addition of aryl halides to aldehydes. In comparison with known approaches using preformed aryl metallic reagents, this reaction is more step-economical and functional group tolerant. The reaction mechanism and a model of stereocontrol were proposed based on experimental and computational results.
Asunto(s)
Aldehídos , Compuestos Heterocíclicos , 2,2'-Dipiridil , Aldehídos/química , Catálisis , Ligandos , Níquel/química , EstereoisomerismoRESUMEN
3-Silylated furfurals, readily prepared in three steps from biomass-derived furfural and 5-methylfurfural, are converted into 3-silylated 2-furyl carbinols upon condensation with organomagnesium or organolithium reagents. The hydroxy unit of the carbinol adducts can be exploited to promote C3(sp2)-Si bond functionalization through intramolecular activation. Two approaches were contemplated for this purpose. Activation by alkoxides of the C3-SiEt3 or C3-SiMe2 t-Bu bonds was ineffective. Conversely, treatment of the C3-benzyldimethylsilyl-appended derivatives with tetrabutylammonium fluoride led to cyclic siloxanes, which revealed to be competent donors for copper-catalyzed cross-coupling reactions, such as arylation reactions catalyzed by Pd2(dba)3/CuI, as well as allylation and methylation reactions catalyzed by CuIâ PPh3. C3-Benzyldimethylsilyl-appended furfurals are thus introduced as versatile platforms, providing a modular access to 3-substituted 2-furyl carbinols from renewable feedstock.
RESUMEN
N,N-Dimethylaziridine-2-carboxamides react with organolithium reagents yielding 2-aziridinylketones. The reaction with one equivalent of organolithium compound is selective to amide carbonyl at a low (-78 °C) temperature. These ketones, in reaction with organolithium reagents, give symmetrical and unsymmetrical aziridinyl carbinols. The usage of excess phenyllithium may serve as a special N-Boc-protecting group cleavage method for acid-sensitive substrates.
Asunto(s)
Aziridinas/química , Cetonas/química , Litio/química , Metanol/química , Estructura Molecular , Compuestos Organometálicos/química , EstereoisomerismoRESUMEN
In this work, we present a simple way to achieve 4-arylselanyl-1H-1,2,3-triazoles from selenium-containing carbinols in a one-pot strategy. The selenium-containing carbinols were used as starting materials to produce a range of selanyl-triazoles in moderate to good yields, including a quinoline and Zidovudine derivatives. One-pot protocols are crucial to the current concerns about waste production and solvent consumption, avoiding the isolation and purification steps of the reactive terminal selanylalkynes. We could also isolate an interesting and unprecedented by-product with one alkynylselenium moiety connected to the triazole.
RESUMEN
An efficient asymmetric hydroesterfication of diarylmethyl carbinols is developed for the first time with a Pd-WingPhos catalyst, resulting in a series of chiral 4-aryl-3,4-dihydrocoumarins in excellent enantioselectivities and good yields. The method features mild reaction conditions, a broad substrate scope, use of easily accessible starting materials, and low palladium loadings. A plausible stereochemical model is also proposed with the Pd-WingPhos catalyst. This method has enabled a 4-step asymmetric synthesis of (R)-tolterodine from readily available starting materials.
RESUMEN
Silver-mediated hydroazidation of unactivated alkynes has been developed as a new method for the synthesis of vinyl azides. Density functional theory calculations toward this reaction reveal that terminal alkynes with TMS-N3 participated hydroazidation proceed through HN3 formation, deprotonation and silver acetylides formation, nucleophilic addition, and protonation of terminal carbon by AgHCO3 . It is also found that water molecules and activation modes of Ag (I) have a significant influence on the title reaction mechanism. Initially, catalyst Ag2 CO3 coordinates preferentially with internal N atom of TMS-N3 to assist water as hydrogen source and proton-shuttle in facilitating HN3 formation. Then, the regioselective anti-addition of HN3 to triple bond of active silver-acetylide or ethynyl carbinols affords product vinyl azide via Ag-C σ-bond activation or Ag C π-coordination activation modes, and the former one is more favorable. The origin of the difference regioselectivity is ascribed to the electronic and orbital effects of the reactive sites. Moreover, Ag2 CO3 is the critical catalyst, acting as activator, base, and stabilizer to promote the HN3 and vinyl azide formation. Water molecule plays an important role as proton shuttle to promote HN3 and key active silver acetylides formation, thus improving the yield of product. © 2017 Wiley Periodicals, Inc.
RESUMEN
The hydroazidation of alkynes is the most straightforward pathway to synthetically useful vinyl azides. However, a general hydroazidation of alkynes remains elusive. Herein, a chemo- and regioselective transformation of ethynyl carbinols into vinyl azides is described. This reaction produces a wide variety of 2-azidoallyl alcohols with high efficiency and in good to excellent yields. These compounds constitute a new class of densely functionalized synthetic intermediates. Their synthetic potential has been demonstrated by further transformations into NHâ aziridines. The mechanistic aspects of the reaction will attract the attention of chemists working on alkyne chemistry and silver catalysis. The findings that are described in this paper represent significant advances in the regioselective hydroelementation of alkynes and open a new reaction manifold for exploitation.
RESUMEN
Illumination by acetylene: Systematic structural variations in a series of archetypal acetylenic lipids derived from the naturally occurring (S,E)-icos-4-en-1-yn-3-ol allowed the discovery of a series of 3R-like 1,4-di-unsaturated carbinol units with a significant and systematic enantiomeric effect on cytotoxicity.