16493-63-3Relevant academic research and scientific papers
Stereoselective synthesis of cis- or trans-2,4-disubstituted butyrolactones from Wynberg lactone
Ganta, Ashok,Shamshina, Julia L.,Cafiero, Lauren R.,Snowden, Timothy S.
experimental part, p. 5396 - 5405 (2012/09/08)
(R)-Wynberg lactone was used to prepare various asymmetric 2,4-disubstituted butyrolactones in three to four steps. Attainment of any possible stereoisomer, based upon commencement from (R)- or (S)-4- trichloromethyl-2-oxetanone, and the capacity to insta
Catalytic asymmetric formation of δ-Lactones from Unsaturated acyl halides
Tiseni, Paolo S.,Peters, Rene
supporting information; experimental part, p. 2503 - 2517 (2010/09/03)
Previously unexplored enantiopure zwitterionic ammonium dienolates have been utilized in this work as reactive intermediates that act as diene components in hetero-Diels-Alder reactions (HDAs) with aldehydes to produce optically active δ-lactones, subunits of numerous bioactive products. The dienolates were generated in situ from E/Z mixtures of a,b- unsaturated acid chlorides by use of a nucleophilic quinidine derivative and Sn (OTf)2 as co-catalyst. The latter component was not directly involved in the cycloaddition step with aldehydes and simply facilitated the formation of the reactive dienolate species. The scope of the cycloaddition was considerably improved by use of a complex formed from Er- (OTf)3 and a simple commercially available norephedrine-derived ligand that tolerated a broad range of aromatic and heteroaromatic aldehydes for a cooperative bifunctional Lewis-acid-/ Lewis-base-catalyzed reaction, providing a,b-unsaturated d-lactones with excellent enantioselectivities. Mechanistic studies confirmed the formation of the dienolate intermediates for both catalytic systems. The active ErIII complex is most likely a monomeric species. Interestingly, all lanthanides can catalyze the title reaction, but the efficiency in terms of yield and enantioselectivity depends directly on the radius of the Ln III ion. Similarly, use of the pseudolanthanides ScIII and YIII also resulted in product formation, whereas the larger La III and other transition metal salts, as well as main group metal salts, proved to be inefficient. In addition, various synthetic transformations of 6- CCl3- or 4-silyl-substituted α,β-unsaturated d-lactones, giving access to a number of valuable δ-lactone building blocks, were investigated.
Polymeric Cinchona Alkaloids as Catalysts in the Enantioselective 2,2-Cycloaddition Reaction of Ketene and Chloral
Song, Choong Eui,Ryu, Tae Hee,Roh, Eun Joo,Kim, In O,Ha, Hyun-Joon
, p. 1215 - 1218 (2007/10/02)
Poly(cinchona alkaloid-co-acrylonitrile) 1a-d and poly(cinchona alkaloid acrylate) 2a-b catalyze the enantioselective cycloaddition of ketene to chloral for the preparation of (R)- and (S)-β-(trichloromethyl)-β-propiolactone.Copolymers 1a-d showed relatively lower catalytic activity with moderate enantioselectivity (22-59percent e.e.), while homopolymers 2a-b gave similar catalytic activity and enantioselectivity (60-94percent e.e.) compared to those of their monomeric alkaloids as catalysts.The polymeric effect was observed with poly(acryloyl quinidine) 2a as catalyst to get the best enantioselectivity of 94percent e.e. at the temperature -30 deg C.
Asymmetric Synthesis of (S)- and (R)-Malic Acid from Ketene and Chloral
Wynberg, Hans,Staring, Emiel G. J.
, p. 166 - 168 (2007/10/02)
Quinidine (5) catalyzes the addition of ketene (1) to chloral (2) at -50 deg C in toluene.The β-(trichloromethyl)-β-propiolactone 3 is formed virtually optically pure (98percent enantiomeric excess).A mechanism for this reaction, accounting for the high enantiomeric excess, is proposed.Known hydrolytic procedures convert the lactone 3 to malic acid (6).By proper choice of catalyst both (R)- and (S)-malic acid can be obtained optically pure.
