155795-48-5Relevant academic research and scientific papers
Lewis acid mediated asymmetric Diels-Alder reactions of chiral 2-phosphonoacrylates
Zhu, Jia-Liang,Chen, Po-Erh,Huang, Hue-Wen
, p. 23 - 36 (2013/02/23)
2-Phosphonoacrylates containing four chiral alcohol auxiliaries were efficiently prepared and evaluated in Lewis acid mediated Diels-Alder reactions. Under the activation of SnCl4, all reactions performed in CH 2Cl2 at -65 °C exclusively afforded the endo (endo-to-carboxylate) cycloadducts with dr's ranging from 50:50 to >99:1. The best facial selectivity was obtained from the substrate bearing a (-)-phenylmenthyl group, to give adducts as (dr >99:1) or almost as (dr = 99:1) single diastereomers. Detailed strategies for the structural elucidation of the cycloadducts as well as a rationalization of the observed stereoselectivity are described.
Chiral auxiliary based reductive alkylation of α, α-diallkyl β-phosphonyl esters
Bau, Jr-Sheng,Chen, I-Chia,Yang, Zhen-Xing,Zhu, Jia-Liang
, p. 531 - 541 (2013/07/27)
Acyclic α, α-disubstituted β-phosphonyl esters containing chiral alcoholic auxiliaries were efficiently prepared and evaluated for the lithium naphthalenide-mediated asymmetric reductive alkylation. Among which, the best diastereoselectivity was received fromthe substrates bearing a (-)-phenylmenthyl group in leading to alkylated esters with up to 83:17 dr. The diastereoselectivity is proven to be controlled by the π-facial differentiation created by the chiral ester as well as the geometry of tetrasubstituted enolates generated by the reductive cleavage of C-P bond.
Total synthesis of (-)-chokol A by an asymmetric domino Michael addition-Dieckmann cyclization
Groth, Ulrich,Kesenheimer, Christian,Kreye, Paul
, p. 2223 - 2226 (2007/10/03)
A convergent and asymmetric total synthesis of (-)-chokol A was accomplished in six steps starting from the α,β-unsaturated ester (E)-9 in an overall yield of 27% with an enantiomeric excess of 95%. The key step of this synthesis is the asymmetric tandem conjugate addition-Dieckmann cyclization of the higher-order cuprate 8 derived from vinyl bromide 7 with the α,β-unsaturated ester (E)-9. Georg Thieme Verlag Stuttgart.
3-Substituted and 2,3-Disubstituted Cyclopentanones via an Asymmetric Tandem 1,4-Addition/Dieckmann Cyclization
Groth, Ulrich,Halfbrodt, Wolfgang,Kalogerakis, Aris,K?hler, Thomas,Kreye, Paul
, p. 291 - 294 (2007/10/03)
A new stereoselective method for the synthesis of 3-substituted and 2,3-disubstituted cyclopentanones is described. The key step is the 1, 4-addition of a cuprate to a chilar Michael-acceptor derived from (-)-8-phenylmenthol or the Helmchen auxiliary followed by Dieckmann cyclization of the obtained chiral enolates. The resultant 2,3-cyclopentanones can be transformed after methanolysis and demethoxycarbonylation to the related 3-substituted cyclopentanones.
Radical cyclizations - Synthesis of γ-lycorane
Cossy, Janine,Tresnard, Ludovic,Pardo, Domingo Gomez
, p. 1925 - 1933 (2007/10/03)
(+)-γ-Lycorane has been synthesized in ten steps from piperonylic alcohol. Two radical reactions were used successively to build the D and B rings. A formal synthesis of (+)-γ-lycorane was achieved via an optically active unsaturated aldehyde intermediate
Reagent control of geometric selectivity and enantiotopic group preference in asymmetric Horner-Wadsworth-Emmons reactions with meso- dialdehydes
Tullis, Joshua S.,Vares, Lauri,Kann, Nina,Norrby, Per-Ola,Rein, Tobias
, p. 8284 - 8294 (2007/10/03)
Results from asymmetric Horner-Wadsworth-Emmons reactions between chiral phosphonate reagents 3a-d, which contain (1R,2S,5R)-8-phenylmenthol as a chiral auxiliary, and mesodialdehydes 6 and 14 are presented. It was found that both the geometric selectivities and the levels of asymmetric induction depended on the structure of the phosphonate (i.e., the alkyl group R1 in the phosphoryl unit) and to a certain extent also on the reaction conditions. Furthermore, the nature of the protecting group used on the α-oxygen substituent in dialdehydes 14 influenced the outcome somewhat. By an appropriate choice of reagent and conditions, either (E)- or (Z)-monoaddition products could be obtained geometrically pure and with good to excellent diastereoselectivities, in synthetically useful yields. Analyses of the absolute configurations of the products showed that the (E)-selective reagents (3a-c) and the (Z)-selective phosphonate 3d reacted at opposite enantiotopic carbonyl groups in the substrates. A mechanistic model which accounts for the products formed is presented.
