66972-67-6Relevant academic research and scientific papers
Asymmetric Michael Addition Reactions of Chiral Prop-2-enyl- and But-2-enylphosphonate Anions with Cyclic Enones
Tanaka, Kiyoshi,Ohta, Yoshihisa,Fuji, Kaoru
, p. 8036 - 8043 (1995)
Reactions of anions derived from chiral allyl- and crotylphosphonates with α,β-unsaturated cyclic ketones took place at the γ-position of the reagents and led to diastereomerically enriched products of conjugate addition, suggesting efficient enantiotopic face discrimination caused by remote asymmetric induction.Using mixtures of crotylphosphonates with different E/Z ratios, we found that the E/Z stereochemistry of the reagent was highly translated into the products.A tandem vicinal dialkylation based on Michael addition - enolate methylation was carried out to give the trans α,β-dialkylated product with high selectivity.Oxidative cleavage of the Michael adducts resulted in the formation of the optically active δ-keto aldehyde corresponding to the formal conjugate addition of an acetaldehyde or a propionaldehyde anion equivalent to α,β-unsaturated carbonyl compounds.
Anodic oxidations of electron-rich olefins: Radical cation based approaches to the synthesis of bridged bicyclic ring skeletons
Reddy, S.Hari Krishna,Chiba, Kazuhiro,Sun, Yongmao,Moeller, Kevin D
, p. 5183 - 5197 (2007/10/03)
The use of intramolecular anodic olefin coupling reactions for building bicyclo[3.2.1]octane ring skeletons has been examined. While simple model systems using bis enol ether substrates readily led to the formation of bicyclic products, application of the reactions to total synthesis efforts were hindered by reactions forming dimethoxy acetal groups at both the terminating and initiating ends of the cyclization reactions. In an effort to solve this problem, ketene acetal based initiating groups have been studied. The use of a ketene dithioacetal group proved especially useful for this purpose.
Synthesis of homochiral 3-substituted cyclopentanones from 2-norbornanones
Martinez, A. Garcia,Teso Vilar,Garcia Fraile,De La Moya Cerero,Martinez Ruiz,Subramanian
, p. 2177 - 2180 (2007/10/03)
The cleavage of the C1-C2 bond in norbornate derivatives is accomplished by base-promoted hydrolysis of α-nitroketones, periodate oxidation or Beckmann fragmentation of suitable precursors prepared from the 2-norbornanones 1. These reactions are the basis for the synthesis of the 3-substituted homochiral cyclopentanones 6, 10 or 15.
Asymmetric Michael Addition Reaction of Phosphorus-Stabilized Allyl Anions with Cyclic Enones
Denmark, Scott E.,Kim, Jung-Ho
, p. 7535 - 7547 (2007/10/03)
The asymmetric Michael addition reaction of chiraly modified P-allyl anions derived from enantiomerically ebriched 2-allyl-1,3,2-oxazaphosphorinane 2-oxides has been investigated with cyclic enones.The racemic 1,3,2-oxazaphosphorinane 2-oxide 3 has been shown to be extremely diastereoselective in the Michael addition to 5-, 6-, and 7-ring enones.With the enantiomerically enriched 2-allyl-1,3,2-oxazaphosphorinane 2-oxides, high regio- and diastereoselectivities (88-90percent diastereomeric excess) have been achieved in the Michael addition reaction of one of the diastereomers (cis series).The Michael reaction of the anions derived from the trans series were not diastereoselective (ca. 10percent diastereomeric excess).The origin of the addition selectivity can be rationalized by (1) consideration of the structure and conformational preferences of the allyl anion (parallel conformation, s-trans, no lithium contact), (2) conformational analysis of the 1,3,2-oxazaphosphorinane 2-oxide ring (chair, equatorial allyl group) and (3) assumption of a 10-membered ring transition state structure with lithium coordination of the enone.
