36677-30-2Relevant academic research and scientific papers
Titanium tetraiodide-promoted reductive enolate formation of α-tosyloxy ketone derivatives and aldol reaction with aldehydes
Hachiya, Iwao,Inagaki, Takao,Ishihara, Yasuhisa,Shimizu, Makoto
experimental part, p. 419 - 421 (2011/05/16)
Titanium tetraiodide-promoted reductive enolate formation from α-tosyloxy ketone derivatives and subsequent aldol reaction of the resulting enolates with aldehydes gave β-hydroxy ketones.
Sml2-promoted reformatsky-type coupling reactions in exceptionally hindered contexts
Sparling, Brian A.,Moslin, Ryan M.,Jamison, Timothy F.
supporting information; experimental part, p. 1291 - 1294 (2009/04/08)
Highly substituted, very hindered enones were synthesized using a two-step procedure that utilizes a diiodosamarium-promoted Reformatsky-type coupling and dehydration using Martin sulfurane. Both α-chloro- and α-bromoketones were coupled with a variety of carbonyl nucleophiles to form the intermediate β-hydroxyketones, occurring with excellent diastereoselectivity, favoring the syn isomer (R1 = Me). This technique complements other methods and enables the preparation of enones outside of the scope of current olefination methodology.
Chiral base-catalyzed aldol reaction of trimethoxysilyl enol ethers: Effect of water as an additive on stereoselectivities
Orito, Yuya,Hashimoto, Shunichi,Ishizuka, Tadao,Nakajima, Makoto
, p. 390 - 400 (2007/10/03)
An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate is described. The aldol reaction of trimethoxysilyl enol ether derived from cyclohexanone under anhydrous conditions predominantly afforded the anti-aldol adduct with moder
From allylic alcohols to aldols through a new nickel-mediated tandem reaction: Synthetic and mechanistic studies
Cuperly, David,Petrignet, Julien,Crevisy, Christophe,Gree, Rene
, p. 3261 - 3274 (2008/09/18)
Nickel hydride type complexes have been successfully developed as catalysts for the tandem isomerization-aldolization reaction of allylic alcohols with aldehydes. Optimization of the reaction conditions has shown that a cocatalyst, such as MgBr2, has a very positive effect on the kinetics of the reaction and in the yields of aldols. Under such optimized conditions {[NiHCl(dppe)] + MgBr2 at 3-5 mol %)}, this reaction affords the aldols in good to excellent yields. It is a full-atom-economy-type reaction that occurs under mild conditions. Furthermore, it has a broad scope for the allylic alcohols and it is compatible with a wide range of aldehydes, including very bulky derivatives. The reaction is completely regioselective, but it exhibits a low stereoselectivity, except for allylic alcohols with a bulky substituent at the carbinol center. The use of chiral non-racemic catalysts was not successful, affording only racemic compounds. However, it was possible to use asymmetric synthesis for the preparation of optically active aldols. Various mechanistic studies have been performed using, for instance, a deuterated alcohol or a deuterated catalyst. They gave strong support to a mechanism involving first a transition-metal-mediated isomerization of the allylic alcohol into the free enol, followed by the addition of the latter intermediate onto the aldehyde in an "hydroxyl-carbonyl-ene" type reaction. These results confirm that allylic alcohols can be considered as new and useful partners in the development of the aldol reaction.
Ytterbium Trifluoromethanesulfonate Mediated Cross-Aldol Reaction between Ketones and Aldehydes
Fukuzawa, Shin-ichi,Tsuchimoto, Teruhisa,Kanai, Takeshi
, p. 2227 - 2232 (2007/10/02)
The cross-aldol reaction between a ketone and an aldehyde proceeded smoothly with threo diastereoselection favorably mediated by ytterbium trifluoromethanesulfonate and tertiary amine in diethyl ether or in dichloromethane.A ytterbium enolate was trapped
Enolboration. 4. An Examination of the Effect of the Leaving Group (X) on the Stereoselective Enolboration of Ketones with Various R2BX/Et3N. New Reagents for the Selective Generation of either Z or E Enol Borinates from Representative Ketones
Brown, Herbert C.,Ganesan, Kumaraperumal,Dhar, Raj K.
, p. 147 - 153 (2007/10/02)
A smooth, rapid, quantitative and stereoselective enolboration of representative ketones to either Z or E enol borinates is achieved with many new R2BX/Et3N reagents.Representative B-X-9-BBN and Chx2BX reagents with various leaving groups, such as triflat
Enolboration. 5. An Examination of the Effects of Amine, Solvent, and Other Reaction Parameters on the Stereoselective Enolboration of Ketones with Various Chx2BX Reagents. An Optimized Procedure To Achieve the Stereoselective Synthesis of E Enol Borinate
Ganesan, Kumeraperumal,Brown, Herbert C.
, p. 7162 - 7169 (2007/10/02)
The effects of amine, solvent, concentration, temperature and other reaction parameters in controlling the enolate geometry have been systematically investigated in the present study.A 11B NMR study of the interaction of representative tertiary amines of
Enantioselective Aldol Reactions using Chiral Lithium Amides as a Chiral Auxiliary
Ando, Akira,Shioiri, Takayuki
, p. 1620 - 1621 (2007/10/02)
The enantioselective aldol reaction of ethyl-t-butyl ketone with benzaldehyde in the presence of chiral ligands has been thoroughly investigated.With the lithium amide derived from 2-isopropylamino-1-methoxy-3-methylbutane (3c) as chiral ligand, a chemica
Preparation and reactions of an alkylzinc enolate
Hansen, Marvin M.,Bartlett, Paul A.,Heathcock, Clayton H.
, p. 2069 - 2074 (2008/10/08)
The preparation, characterization, and reactivity of ethylzinc enolate 3 are reported. Enolate 3 is less reactive than the corresponding lithium enolate but undergoes many of the same reactions. The unprecedented protonation of 3 by secondary amines is reported. The metal exchange reaction used to prepare 3 is not a general method for the preparation of other alkylzinc enolates.
Acyclic Stereoselection. 36. Simple Diastereoselection in the Lewis Acid Mediated Reactions of Enol Silanes with Aldehydes
Heathcock, Clayton H.,Davidsen, Steven K.,Hug, Kathleen T.,Flippin, Lee A.
, p. 3027 - 3037 (2007/10/02)
The Lewis acid mediated aldol reactions of enol silanes with aldehydes have been investigated.The effects of enol silane structure, both nature of the ligand at the silyloxy carbon and the geometry of the double bond, the aldehyde structure, and the nature of the Lewis acid have been studied.In general, the reactions of prochiral enol silanes with prochiral aldehydes show little simple diastereoselection (Table I).An exception is Z enol silane 7, derived from ethyl tert-butyl ketone, which shows synthetically useful anti selectivity.Enol silane 36 may therefore be used as an anti-selective propionate equivalent.The chiral α-alkoxy aldehyde 43 shows a high diastereofacial preference in its reactions with enol silanes 42c and 42d provided a Lewis acid capable of expanding its coordination beyond four is used (TiCl4 or SnCl4) (Table II).However, with the related ketene acetal 41b, only modest diastereofacial selectivity is seen (Table II).Aldehyde 43 also shows a high diastereofacial preference, in the chelation-controlled sense, in its reactions with prochiral enol silanes 5-9.However, the simple diastereoselection observed in the latter reactions (Table III) is quite different from that observed in the reactions of prochiral aldehydes with the same enol silanes.For example, enol silane 7, which shows good anti selectivity in its reactions with prochiral aldehydes, gives a 15:1 mixture of the two syn aldols in its reaction with 43; while the reverse is true with the propiophenone-derived enol silanes 8 and 9.Finally, the results obtained in this study, along with those reported by other investigators, have been formulated into a coherent mechanistic rationale involving open transition states of the sort depicted in Figures 1 and 3.
