7204-29-7Relevant articles and documents
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.
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.
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.
