2129-95-5Relevant academic research and scientific papers
Biocatalytic asymmetric and enantioconvergent hydrolysis of trisubstituted oxiranes
Steinreiber, Andreas,Mayer, Sandra F.,Saf, Robert,Faber, Kurt
, p. 1519 - 1528 (2001)
Asymmetric biohydrolysis of trialkyl oxiranes (±)-1a-3a using the epoxide hydrolase activity of whole bacterial cells proceeded in an enantioconvergent fashion and thus led to the corresponding (R)-configurated vicinal diols 1b-3b in up to 97% enantiomeric excess (e.e.) as the sole product. The mechanism of this enantioconvergence was investigated by 18O-labelling experiments and it was found that both enantiomers were hydrolysed with opposite regioselectivity.
Superelectrophilic Fe(III)-Ion Pairs as Stronger Lewis Acid Catalysts for (E)-Selective Intermolecular Carbonyl-Olefin Metathesis
Albright, Haley,Schindler, Corinna S.,Vonesh, Hannah L.
supporting information, p. 3155 - 3160 (2020/04/21)
An intermolecular carbonyl-olefin metathesis reaction is described that relies on superelectrophilic Fe(III)-based ion pairs as stronger Lewis acid catalysts. This new catalytic system enables selective access to (E)-olefins as carbonyl-olefin metathesis products. Mechanistic investigations suggest the regioselective formation and stereospecific fragmentation of intermediate oxetanes to be the origin of this selectivity. The optimized conditions are general for a variety of aryl aldehydes and trisubstituted olefins and are demonstrated for 28 examples in up to 64% overall yield.
A Relay Strategy Actuates Pre-Existing Trisubstituted Olefins in Monoterpenoids for Cross-Metathesis with Trisubstituted Alkenes
Bahou, Karim A.,Braddock, D. Christopher,Meyer, Adam G.,Savage, G. Paul,Shi, Zhensheng,He, Tianyou
, p. 4906 - 4917 (2020/04/10)
A retrosynthetic disconnection-reconnection analysis of epoxypolyenes - substrates that can undergo cyclization to podocarpane-type tricycles - reveals relay-actuated Δ6,7-functionalized monoterpenoid alcohols for ruthenium benzylidene catalyzed olefin cross-metathesis with homoprenyl benzenes. Successful implementation of this approach provided several epoxypolyenes as expected (E/Z, ca. 2-3:1). The method is further generalized for the cross-metathesis of pre-existing trisubstituted olefins in other relay-actuated Δ6,7-functionalized monoterpenoid alcohols with various other trisubstituted alkenes to form new trisubstituted olefins. Epoxypolyene cyclization of an enantiomerically pure, but geometrically impure, epoxypolyene substrate provides an enantiomerically pure, trans-fused, podocarpane-type tricycle (from the E-geometrical isomer).
Simple salts of abundant metals (Fe, Bi, and Ti) supported on montmorillonite as efficient and recyclable catalysts for regioselective intramolecular and intermolecular hydroalkoxylation reactions of double bonds and tandem processes
Notar Francesco, Irene,Cacciuttolo, Bastien,Pascu, Oana,Aymonier, Cyril,Pucheault, Mathieu,Antoniotti, Sylvain
, p. 19807 - 19818 (2016/03/01)
The transfer of catalytic hydroalkoxylation reactions of olefins from homogeneous to heterogeneous conditions has been studied using two types of solid catalysts, namely montmorillonite (MMT) doped with metal cations and metal nanoparticles supported on oxides. In the case of intramolecular reactions, 38-99% yields of cyclic ethers have been obtained using Fe-MMT and Bi-MMT both in CH3NO2 and dimethyl carbonate (DMC) compared with other supported metal salts or metal nanoparticles. In the case of more challenging intermolecular reactions, conversions up to 72% and yields up to 54% were obtained with metal-doped MMT as well, such as Fe-, Bi-, and Ti-MMT. In this paper, we detail the substrate scope and limitations for both classes of reactions and tandem processes, their transposition in flow and some mechanistic insights concerning the active species, in processes identified as truly heterogeneously catalysed. As a general trend, it was observed that trisubstituted double bonds allowed the best results both in intra- and intermolecular reactions. The transfer of homogeneous catalysts onto heterogeneous ones in the case of Fe-MMT and Bi-MMT was successful and even allowed enhanced catalytic activities in the case of Bi-MMT.
Alkylation of 2-substituted (6-Methyl-2-pyridyl)methyllithium species with epoxides
Vyvyan, James R.,Brown, Rebecca C.,Woods, Brian P.
supporting information; experimental part, p. 1374 - 1376 (2009/07/04)
Substituted (6-methyl-2-pyridyl)methyllithium species were reacted with 1,2-epoxyoctane and 2-methyl-2,3-epoxynonane. The monosubstituted epoxide reacted efficiently with lutidyllithium and a number of 2-substituted (6-methyl-2-pyridyl)methyllithium deriv
Widely applicable Pd-catalyzed trans-selective monoalkylation of unactivated 1,1-dichloro-1-alkenes and Pd-catalyzed second substitution for the selective synthesis of E or Z trisubstituted alkenes
Tan, Ze,Negishi, Ei-Ichi
, p. 762 - 765 (2007/10/03)
(Chemical Equation Presented) Double substitution: The first selective and widely applicable method for a step-wise alkylation of 1,1-dichloro-1-alkenes involving a cross-coupling double substitution using Pd-catalysis has been developed. This method provides an efficient and highly selective route for the synthesis of E or Z trisubstituted alkenes. dpephos = bis(o- diphenylphosphanylphenylether).
Organic synthesis with sulphones no. XXXIV. Uncatalysed addition versus nickel catalysed coupling reaction of vinylic sulfones with Grignard reagents. A stereoselective synthesis of olefins and dienes
Fabre, Jean-Luc,Julia, Marc,Verpeaux, Jean-Noel
, p. 762 - 771 (2007/10/02)
Grignard reagents undergo Michael addition to vinylic sulfones.With a β-β-disubstituted vinylic sulfone an unexpected dimer is obtained.Under nickel catalysis methyl, aryl and alkenyl Grignard reagents displace the sulfonyl group of the readily available α,β-unsaturated sulfones.Methyl, resp. phenyl substituted olefins or conjugated dienes are formed.Under appropriate conditions the reaction proceeds with complete retention of configuration.
OLEFINATION OF KETONES USING 1,1-DIMETALLOALKANES DERIVED FROM i-Bu2AlCH=CHR - Cl2TiCp2 SYSTEM
Yoshida, Tadao
, p. 429 - 432 (2007/10/02)
The alkylidenation of ketone carbonyls using 1,1-dimetalloalkanes prepared by the reaction of 1-alkenyldiisobutylalanes with titanocene dichloride afforded the corresponding olefins in good yields.
Anwendungen der Phasentransfer-Katalyse 17. Wittig-Reaktionen in verschiedenen Zweiphasen-Systemen
Dehmlow, Eckehard V.,Barahona-Naranjo, Simon
, p. 1748 - 1762 (2007/10/02)
EINE vergleichende Untersuchung von Wittig-Reaktionen unter Phasentransfer-Katalyse (PTC) bei verschiedenen Bedingungen wurde durchgefuehrt.Es erwies sich als unnoetig, ausser den Phosphoniumsalzen einen PTC-Katalysator zu verwenden.Mechanistische Konsequenzen dieses Befundes werden diskutiert.Als ein besonders geeignetes Basensystem stellte sich Kalium-tert-butoxid in Benzol heraus.Erstmals gelang die Umzetzung von Ketonen und aliphatischen Aldehyden.Einige sehr hohe Literaturausbeuten von PTC-Wittig-Reaktionen konnten unter praeparativen Bedingungen nicht reproduziert werden.
