Thioesters allylic

Asymmetric Synthesis of Allylic Thioesters and Kinetic Resolution of Allylic Esters... 

The Pd-catalyzed enantioselective allylic alkylation of thiols in the presence of BPA is limited to aryl and heteroaryl thiols [10]. However, allylic thioesters should... 

Scheme 2.1.4.21 Pd(0)/BPA-catalyzed asymmetric synthesis of allylic thioesters.

Dienes coordinated to iron tricarbonyl do not undergo Diels-Alder reactions and a number of interesting annulation reactions of groups attached to iron tricarbonyl diene complexes have been developed. Cyclohexadiene iron tricarbonyl complexes having a pendant alkene undergo annulation reactions to form spirocychc compounds (Scheme 160). Related reactions of allylic thioesters afford spirocychc thialac-tones. 

This ligand was also involved by Gais and colleagues in the Pd-catalysed enantioselective allylic alkylation of thiocarboxylate ions with allylic esters. " This novel DYKAT has allowed the access to highly enantio-enriched acyclic allylic thioesters in good to high yields, as shown in Scheme 2.56. 

Diene)Fe(GO)3 complexes have been used to construct 2-azaspiro[5.5]undecane and tricyclic ring systems. Intramolecular coupling reactions between diene-Fe(GO)3 complexes and a pendant olefinic group or pendant alcohols have been studied.The cyclization of allylic thioester-functionalized cyclohexadiene iron tricarbonyl... 

Gold(I)-catalysed ring-opening of 3,3-disubstituted cyclopropenes (249) with thiols, thiophenols, and thioacids has been shown to occur regio- and chemo-selectively, producing either vinyl thioethers (250) or primary allylic thioesters (251), depending on the ligands coordinated to Au and the nature of the nucleophile. ... 

These ideas will be discussed in the following subsections, where most of the attention will be devoted to the mechanistic smdies with aromatic esters, which have been the subject of an overwhelming majority of the research efforts. Nevertheless, the same reaction mechanism has been shown to be valid for the PFR of anilides, thioesters, sulfonates, and so forth. Furthermore, it is also applicable to the photo-Claisen rearrangement [i.e. the migration of alkyl (or allyl, benzyl, aryl,)] groups of aromatic ethers to the ortho and para positions of the aromatic ring [21,22]. 

To the best of our knowledge, the allylation of dithianes has not been previously reported in the literature. A range of dithianes underwent smooth allylation to give the desired thioester products in good yield however, a slightly increased catalyst loading (2-10 mol%) was needed (Table 8). 

The Pd-catalyzed allylic alkylation of thiocarboxylate ions was carried out with potassium thioacetate (KSAc) and potassium thiobenzoate (KSBz) and the racemic cyclic and acyclic carbonates rac-3aa, rac-3ba, rac-lda, rac-laa, rac-lba, and rac-lca, respectively (Scheme 2.1.4.21). The carbonates rac-3aa, rac-3ba, rac-lda, rac-laa, and rac-lba were treated with KSAc (1.4 equiv) or KSBz (2.0 equiv) in the presence of Pd(0)/L (2 mol%) and BPA (8 mol%) in CH2CI2/H2O. Under these conditions the acyclic carbonates rac-3aa and rac-3ba gave the thioesters 18aa, 18ab and 18ba, respectively (Table 2.1.4.14, entries 1-3), with high enantioselec-tivities in high yields [26]. 

The Pd-catalyzed allylic alkylation of sulfinate ions, thiols, and thiocarboxylate ions with racemic cyclic and acyclic allylic esters in the presence of bisphosphane BPA generally provides for an efficient asymmetric synthesis of allylic sulfones, sulfides, and thioesters. The Pd-catalyzed rearrangements of allylic sulfinates and allylic O-thiocarbamates, both of which proceed very efficiently in the presence of BPA, are attractive alternative ways to the asymmetric synthesis of allylic sulfones and allyUc thioesters also starting from the corresponding racemic alcohols. 

Aryl homoallyl ketones and 4-methoxy phenyl ethers are also good substrates for the AD [8], whereas the structurally related allyl amides and thioesters give products with insufficient enantioselectivity. Homoallylic 4-methoxy benzoates perform relatively poor, which is consistent with Corey s proposed mechanistic model [9],... 

To address limitations in the use of glyceraldehyde acetonide (43) as a three-carbon chiral building block, butane-2,3-diacetal-protected glyceraldehyde (44, R1 = R2 = H) has been prepared. It undergoes diastereoselective aldol reactions with a range of carbonyl compounds esters, thioesters, and ketones. The work has been extended (g) to other derivatives such as the a-substituted aldehyde (44, R1 = Me, allyl) and the methyl ketone (44, R2 = Me).122a,b... 

The construction of the maleic anhydride moiety 44 in only five steps starts with the conversion of the amide into an appropriate thioester. Upon treatment with DBU, an aldol-type cyclization occurs to provide the /1-hydroxy thiolactone as a single diastereomer. After removal of the allylic protecting group, dehydration and decarboxylation are carried out simultaneously by simple heating. The thiobutenolide is oxidized to the corresponding thio-... 

Kim further developed the alkyl allyl suhbne-based chemistry, and disclosed a carbonylation reaction to prepare thioesters (Scheme 43) [128,129]. 

Esters. Reductive carbonylation in the presence of an alcohol or phenol leads to an ester. Substrates include organoiodonium salts and allylic alcohols. p,y-Unsaturated thioesters can be generated by the method or from allenes. Note that y-lactones are formed when allylic alcohols are carbonylated without additives. ... 

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