7204-29-7Relevant academic research and scientific papers
Stereospecific thio-Claisen rearrangement of S-crotylic α-hydroxy ketene dithioacetals. Creation of three contiguous stereogenic centres
Beslin, Pierre,Perrio, Stephane
, p. 3131 - 3142 (1993)
All four diastereoisomeric S-crotylic α-hydroxy ketene dithioacetals (ZE′, ZZ′, EE′ and EZ′) were prepared uniquivocally from S-methyl or S-crotyl (Z or E) β-hydroxy dithioesters by a tandem cis-deprotonation with LDA and S-alkylation. These dithioacetals underwent, in a refluxing cyclohexane solution, an easy thio-Claisen rearrangement into dithioesters, containing three contiguous chiral centres. The rearrangement is stereospecific. Furthermore each of the four system led to the formation of a different major diastereoisomer, thus making all of the four possible isomers (anti-anti, syn-syn, anti-syn and syn-anti) accessible. A relationship between the main component configuration and the starting dithioacetal geometry has been ruled out. The observed stereospecificity originates from two independent stereocontrols, an internal and an external one. The former is an aggreement with the classical internal control obtained with a [3.3] sigmatropic shift. The latter is a result of an asymmetric induction but surprisingly, is dependent on the S-crotylic double bond geometry. All the results were rationalised by transition state models and the configurations proven by chemical correlations: transformation into known esters and Swern oxidation.
Selecting double bond positions with a single cation-responsive iridium olefin isomerization catalyst
Camp, Andrew M.,Kita, Matthew R.,Blackburn, P. Thomas,Dodge, Henry M.,Chen, Chun-Hsing,Miller, Alexander J.M.
supporting information, p. 2792 - 2800 (2021/03/01)
The catalytic transposition of double bonds holds promise as an ideal route to alkenes of value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, normally requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst selectively produces either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on noncovalent modifications.
In(OTf)3-catalysed easy access to dihydropyranocoumarin and dihydropyranochromone derivatives
Boufroua, Naouel,Dunach, Elisabet,Fontaine-Vive, Fabien,Poulain-Martini, Sophie,Boufroua, Naouel,Achouche-Bouzroura, Samia
supporting information, p. 6042 - 6052 (2020/04/27)
We developed an easy, In(OTf)3-catalysed, regioselective and generalizable method, for allylation/cyclization of β-ketolactone-type heterocyclic compounds. This reaction is proposed to proceed one-pot, through a Friedel-Crafts C-allylation followed by cyclization. This process represents a green synthetic method, as AcOH is the only isolated byproduct. We propose here, a protocol applicable for the construction of biologically active dihydropyranocoumarin and dihydropyranochromone derivatives.
The multiple roles of imidazolium ionic liquids in transition-metal catalysis: The palladium-catalyzed telomerization of 1,3-butadiene with acetic acid
Balbino, Jo?o M.,Peral, Daniel,Bay?n, J. Carles,Dupont, Jairton
, p. 972 - 977 (2015/03/18)
The telomerization of 1,3-butadiene with acetic acid catalyzed by palladium(II) acetate associated with a series of phosphines in 3-(2-methoxyethyl)-1-methylimidazolium acetate was used to investigate the role of the ionic liquid. The ionic liquid plays multiple roles in this reaction as it acts as the solvent, stabilizer, ligand, and cocatalyst. The reaction performed in the presence of Dan2phos, a trifluoromethylated sulfonated triarylphosphine, at 100 °C for 24 h gave a turnover number of 14 600 with 89 % selectivity to telomers at 75 % 1,3-butadiene conversion and complete acetic acid conversion.
Achieving control over the branched/linear selectivity in palladium-catalyzed allylic amination
Dubovyk, Igor,Watson, Iain D. G.,Yudin, Andrei K.
, p. 1559 - 1575 (2013/03/28)
Palladium-catalyzed reaction of unsymmetrical allylic electrophiles with amines gives rise to regioisomeric allylic amines. We have found that linear products result from the thermodynamically controlled isomerization of the initially formed branched products. The isomerization is promoted by protic acid and active palladium catalyst. The use of base shuts down the isomerization pathway and allows for the preparation and isolation of branched allylic amines. Solvent plays a key role in achieving high kinetic regioselectivity and in controlling the rate of isomerization. The isomerization can be combined with ring-closing metathesis to afford the synthesis of exocyclic allylic amines from their endocyclic precursors.
Ni- and pd-catalyzed synthesis of substituted and functionalized allylic boronates
Zhang, Ping,Roundtree, Ian A.,Morken, James P.
supporting information; scheme or table, p. 1416 - 1419 (2012/06/01)
Two highly efficient and convenient methods for the synthesis of functionalized and substituted allylic boronates are described. In one procedure, readily available allylic acetates are converted to allylic boronates catalyzed by Ni/PCy3 or Ni/PPh3 complexes with high levels of stereoselectivity and in good yields. Alternatively, the borylation can be accomplished with commercially available Pd catalysts [e.g., Pd 2(dba)3, PdCl2, Pd/C], starting with easily accessed allylic halides.
Synthesis of saturated 1,4-benzodiazepines via Pd-catalyzed carboamination reactions.
Neukom, Joshua D.,Aquino, Alvin S.,Wolfe, John P.
supporting information; body text, p. 2196 - 2199 (2011/06/25)
Chemical equations presented. A new synthesis of 1,4-benzodiazepines and 1,4-benzodiazepin-5-ones is reported. The Pd-catalyzed coupling of N-allyl-2-aminobenzylamine derivatives with aryl bromides affords the heterocyclic products in good yield, and substrates bearing allylic methyl groups are transformed to cis-2,3-disubstituted products with >20:1 dr.
Cobalt-catalyzed reductive allylation of alkyl halides with allylic acetates or carbonates
Qian, Xin,Auffrant, Audrey,Felouat, Abdellah,Gosmini, Corinne
supporting information; experimental part, p. 10402 - 10405 (2011/12/03)
An efficient method for the direct allylation of alkyl halides catalyzed by simple cobalt(II) bromide has been developed. This reaction, using a variety of substituted allylic acetates or carbonates, provides the linear product as the major product. It displays broad substrate scope and good functional group tolerance. Copyright
A nucleophilic Fe catalyst for transesterifications under neutral conditions
Magens, Silja,Ertelt, Melanie,Jatsch, Anja,Plietker, Bernd
, p. 53 - 56 (2008/09/17)
Carboxylic esters belong to the most important functional groups in organic chemistry. Strong efforts have been made in developing mild catalytic procedures for their preparation. Among the various methods developed to date, transesterifications have occupied an important space. In the present paper, a new catalytic method for this process based on the use of nucleophilic Fe(-II) complexes is presented. Evidence for the formation of an intermediate acyl Fe complex will be presented as well as investigations on scope and limitations.
Chasing the proton culprit from palladium-catalyzed allylic amination
Dubovyk, Igor,Watson, Iain D. G.,Yudin, Andrei K.
, p. 14172 - 14173 (2008/09/18)
We have found that the addition of base has a significant effect on palladium-catalyzed allylic amination. The long-standing problem of controlling the branched-to-linear ratio has been solved. In the presence of DBU and inexpensive, readily available ligands, palladium-catalyzed allylation proceeds under kinetic control, leading to high branched selectivity. Given the widespread utility of palladium-catalyzed allylic amination, we expect that these findings will be relevant in many areas ranging from asymmetric catalysis to target-oriented synthesis. Copyright
