19248-95-4Relevant academic research and scientific papers
Synthesis of tubuphenylalanines via ireland-claisen rearrangement
Becker, Dominic,Kazmaier, Uli
, p. 59 - 65 (2013/03/28)
The Ireland-Claisen rearrangement is the central step in the synthesis of tubuphenylalanine, a key building block of the highly antitumor-active tubulysins. The rearrangement of substituted β-amino acid allyl esters, in combination with subsequent decarboxylation and oxidative cleavage of the double bond, allows the highly stereoselective introduction of substituents into the α-position of the resulting σ-amino acids.
Highly enantioselective synthesis of 3-substituted furanones by palladium-catalyzed kinetic resolution of unsymmetrical allyl acetates
Mao, Bin,Ji, Yining,Fananas-Mastral, Martin,Caroli, Giuseppe,Meetsma, Auke,Feringa, Ben L.
supporting information; experimental part, p. 3168 - 3173 (2012/05/05)
Resolving the issue: A near-perfect Pd-catalyzed kinetic resolution of 1,3-disubstituted unsymmetrical allylic acetates uses silyl enol ethers as nucleophiles to access the important 3-substituted-furanone scaffold (see scheme; DACH=diaminocyclohexyl, dba=dibenzylideneacetone). The reaction proceeds under mild conditions and provides the desired products with excellent chemo-, regio-, and enantioselectivity. Copyright
Palladium-catalyzed enantioselective allylic alkylation of thiocarboxylate ions: Asymmetri synthesis of allylic thioesters and memory effect/dynamic kinetic resolution of allylic esters
Luessem, Bernhard J.,Gais, Hans-Joachim
, p. 4041 - 4052 (2007/10/03)
The palladium-catalyzed allylic alkylation of KSAc and KSBz with racemic cyclic and acyclic allylic esters by using N,N'-(1R,2R)-1,2-cyclohexandiylbis[2-(diphenylphosphino)-benzamide] as ligand frequently gave the corresponding allylic thioesters with high ee values and yields. The reaction of the cyclic allylic carbonates with KSAc in the presence of H20 was accompanied by a partial palladium-catalyzed enantioselective "hydrolysis" of the substrates with formation of the corresponding enantioenriched allylic alcohols. The degree of the "hydrolysis" was strongly dependent on the solvent and the thiocarboxylate ion. Highly selective kinetic resolutions (KRs) were observed in the palladium-catalyzed reaction of the racemic cyclohexenyl and cycloheptenyl acetates with KSAc. While the KR of the cyclohexenyl acetate is characterized by a selectivity factor S = 72 ± 19, that of the cycloheptenyl acetate afforded (R)-cycloheptenyl acetate of ≥ 99% ee in 48% yield and (S)-cycloheptenyl thioacetate of 98% ee in 50% yield. The palladium-catalyzed reaction of the racemic cyclopentenyl acetate with KSAc showed a strong "memory effect" (ME), that is, both enantiomers reacted with different enantioselectivities. The ME was probed by studying the palladium-catalyzed reactions of both the matched acetate of ≥ 99% ee and the mismatched acetate of ≥ 99% ee with KSAc. The acetates not only reacted with different enantioselectivities and rates but also suffered an unexpected and concomitant palladium-catalyzed racemization in the presence of the chiral ligand. This led in the case of the mismatched acetate to a temporary dynamic kinetic resolution (DKR) that featured a racemization of the mismatched acetate by the chiral catalyst. Studies of the palladium-catalyzed reaction of the racemic cyclopentenyl acetate, carbonate, and naphthoate with KSAc in the presence of the chiral ligand also showed the ME to be strongly dependent on the nucleofuge. This also allowed the synthesis of (S)-cyclopentenyl thioacetate of 92% ee in high yield from the racemic cyclopentenyl naphthoate.
