139239-48-8Relevant academic research and scientific papers
Stereoselective preparation of 2-silylated 1,3-diols and the regioselectivity of their peterson olefination
Faessler, Juerg,Linden, Anthony,Bienz, Stefan
, p. 1717 - 1730 (1999)
The reduction of the carbonyl group of α-silylated aldols with complex hydrides was shown to proceed with high stereoselectivity. The center of chirality in the α-position to the ketone, at the C-atom where the silicon group is attached, usually dominated the stereochemical control of the reaction. The presence of the β-hydroxy functionality, however, also seems to be necessary for a high degree of selectivity. Peterson olefination of 2- silylated 1,3-diols afforded stereoselectively (E)-configured allylic alcohols as the major products. With KH as the base, the reaction proceeds predominantly in a syn-fashion, preferring to eliminate a syn- rather than an anti-configured β-hydroxysilane unit. Under 'silico-nucleophilic' conditions (OH- or F-), an anti-configured β-hydroxysilane moiety can also be eliminated in an anti-fashion. This reaction is strongly preferred over the corresponding syn-elimination, but is still less prominent than a competitive syn-elimination of a syn-configured β-hydroxysilane unit.
Enantioselective Conjunctive Cross-Coupling of Bis(alkenyl)borates: A General Synthesis of Chiral Allylboron Reagents
Edelstein, Emma K.,Namirembe, Sheila,Morken, James P.
supporting information, p. 5027 - 5030 (2017/05/04)
Palladium-catalyzed conjunctive cross-coupling is used for the synthesis of enantioenriched allylboron reagents. This reaction employs nonsymmetric bis(alkenyl)borates as substrates and appears to occur by a mechanism that involves selective activation of the less substituted alkene followed by migration of the more substituted alkene during the course of a Pd-induced metalate rearrangement.
Nazarov cyclization of divinyl ketones bearing an ester group at the β-position: A remarkable effect of α-substitution and alkene geometry on regioselectivity
Sudhakar, Gangarajula,Raghavaiah, Jakka,Mahesh, Gaddam,Singarapu, Kiran Kumar
supporting information, p. 2866 - 2872 (2016/03/12)
The Nazarov cyclization of divinyl ketones with an ester at the β-position was examined with particular reference to where the cyclic double bond forms. We observed unprecedented regioselectivity, dictated by the subtle substitution patterns at the α-position and alkene geometry of α,β and mostly, this selectivity is regardless of substitutions at α′- and β′-positions. The major implications of these observations are an aromatic group at the α-position with E-olefin geometry provides a cyclopentenone in which the double bond is not in conjugation with an ester, whereas Z-olefin provides a cyclopentenone in which the double bond is in conjugation with an ester; and divinyl ketones bearing an ester group at the β-position and an alkyl group at the α-position with E-olefin geometry provide a cyclopentenone in which the double bond is in conjugation with the ester.
Chirality Transfer in Gold(I)-Catalysed Direct Allylic Etherifications of Unactivated Alcohols: Experimental and Computational Study
Barker, Graeme,Johnson, David G.,Young, Paul C.,Macgregor, Stuart A.,Lee, Ai-Lan
supporting information, p. 13748 - 13757 (2015/09/22)
Gold(I)-catalysed direct allylic etherifications have been successfully carried out with chirality transfer to yield enantioenriched, γ-substituted secondary allylic ethers. Our investigations include a full substrate-scope screen to ascertain substituent effects on the regioselectivity, stereoselectivity and efficiency of chirality transfer, as well as control experiments to elucidate the mechanistic subtleties of the chirality-transfer process. Crucially, addition of molecular sieves was found to be necessary to ensure efficient and general chirality transfer. Computational studies suggest that the efficiency of chirality transfer is linked to the aggregation of the alcohol nucleophile around the reactive π-bound Au-allylic ether complex. With a single alcohol nucleophile, a high degree of chirality transfer is predicted. However, if three alcohols are present, alternative proton transfer chain mechanisms that Erode the efficiency of chirality transfer become competitive.
O-DPPB-directed copper-mediated and -Catalyzed allylic substitution with grignard reagents
Demel, Peter,Keller, Manfred,Breit, Bernhard
, p. 6669 - 6683 (2008/09/16)
The ortho-diphenylphosphanylbenzoyl (o-DPPB) group was explored as a directing leaving group in copper-mediated and copper-catalyzed allylic substitution with Grignard reagents. Complete control of chemo-, regio- and stereoselectivity with complete syn-1,3-chirality transfer was observed as a result of the directed nature of the reaction. No excess of or ganometallic reagent is required and the directing group can be recovered quantitatively. Coordination studies in the solid state and in solution have shown that two substrates are bound via the phosphine function of the directing group at copper. Dynamic NMR experiments in solution are in agreement with a ligand-exchange process at copper, a prerequisite for the development of a substoichiometric process.
Copper-Mediated and -Catalyzed o-DPPB-Directed Allylic Substitution
Breit, Bernhard,Demel, Peter
, p. 429 - 432 (2007/10/03)
Complete control of chemo-, regio- and stereoselectivity in the course of copper-catalyzed and -mediated allylic substitution could be obtained with me ortho-diphenylphosphanyl (o-DPPB) function as a reagent-directing leaving group. Complete chirality transfer by way of a syn-addition process has been achieved for cyclic and acyclic systems. Readily available Grignard reagents may be employed as nucleophiles and the directing o-DPPB group can be recovered quantitatively. The reaction requires neither cooling nor an excess of organometallic reagent.
Highly S(N)2'-, (E)-, and antiselective alkylation of allylic phosphates. Facile synthesis of coenzyme Q10
Yanagisawa,Nomura,Noritake,Yamamoto
, p. 1130 - 1136 (2007/10/02)
Treatment of secondary allylic chlorides or allylic phosphates in tetrahydrofuran with prenyl Grignard reagent in the presence of CuCN · 2 LiCl gave geraniol or farnesol derivatives with high S(N)2' selectivity. Phosphate leaving groups were highly transstereoselective for the formation of (E,E)-farnesol derivatives. Furthermore, complete anti-S(N)2' selectivity was observed in the alkylation of optically active allylic phosphates. The present method appears to be an excellent carbon-carbon coupling reaction with high regio-, (E)-, and enantioselectivity. Coenzyme Q10 (ubiquinone 10) was efficiently synthesized using this methodology.
