54877-01-9Relevant academic research and scientific papers
Dichloromethane as a source of the CH22-synthon: A combination of an arene-catalysed lithiation and a barbier-type reaction
Guijarro, Albert,Vus, Miguel
, p. 253 - 256 (1994)
The reaction of dichloromethane 1 with an excess of lithium powder (1:7 molar ratio) and catalytic amount of 4,4'-di-tert-butylbiphenyl (5 mol %) in the presence of a carbonyl compound 2 (1:2 molar ratio) in tetrahydrofuran at -40°C yields, after hydrolysis, the corresponding 1,3-diols 3 in moderate yields. The process can be also applied to more complicated gem-dichloro derivatives such as 7,7-dichlorobicyclo[4.1.0]heptane 6 or methyl dichloromethyl ether 9.
The zirconium alkoxide-catalyzed aldol-tishchenko reaction of ketone aldols
Schneider, Christoph,Hansch, Markus,Weide, Timo
, p. 3010 - 3021 (2007/10/03)
The aldol-Tishchenko reaction of ketone aldols as enol equivalents has been developed as an efficient strategy to furnish differentiated 1,3-anti-diol monoesters in one step. The thermodynamically unstable ketone aldols undergo a facile retro-aldolization to yield a presumed zirconium enolate in situ, which then undergoes the aldol-Tishchenko reaction in typically high yields and with complete 1,3-anti diastereocontrol. Evaluation of a broad range of metal alkoxides as catalysts and optimization of the reaction protocol led to a modified zirconium alkoxide catalyst with attenuated Lewis acidity and dichloromethane as solvent, which resulted in suppression of the undesired acyl migration to a large extent. Various ketone aldols have been prepared and subjected to the general process, giving rise to a broad range of differently substituted 1,3-anti-diol monoesters, which may be hydrolyzed to the corresponding 1,3-anti-diols.
Stereocontrolled reductive amination of 3-hydroxy ketones
Haddad, Mansour,Dorbais, Jerome,Larcheveque, Marc
, p. 5981 - 5984 (2007/10/03)
syn-1,3-Aminoalcohols are synthesized in high diastereomeric excess by reductive amination of 3-hydroxyketones with sodium cyanoborohydride in the presence of benzylamine.
In search of open-chain 1,3-stereocontrol
Barbero, Asun,Blakemore, David C.,Fleming, Ian,Wesley, Robert N.
, p. 1329 - 1352 (2007/10/03)
Methylation of methyl 4-phenylpentanoate 25 gives the diastereoisomers methyl (2RS,4SR)-2-methyl-4-phenylpentanoate 26 and methyl (2RS,4RS)- 2-methyl-4-phenylpentanoate 27 in a ratio of 44:56. The aldehydes 3-dimethyl(phenyl)silylbutanal 28, 3-dimethyl(ph
Polychlorinated materials as a source of polyanionic synthons
Guijarro, Albert,Yus, Miguel
, p. 1797 - 1810 (2007/10/03)
The reaction of dichloromethane (1a) or dichlorodideuteriomethane (1b) with an excess of lithium powder (1:7 molar ratio) and a catalytic amount of DTBB (5 mol%) in the presence of a carbonyl compound 2 (1:2 molar ratio) in THF at -40°C yields, after hydrolysis, the corresponding 1,3-diols 3 in moderate yields. The process is applied to other gem-dichlorinated materials such as 7,7-dichloro [4.1.0]heptane (4), 1,1-dichlorotetramethylcyclopropane (7) and dichloromethyl methyl ether (10), using pivalaldehyde as electrophile. Starting from 1,1,1-trichlorinated compounds or tetrachloromethane (14) and using chlorotrimethylsilane as electrophile at temperatures ranging between -80 and -90°C, the corresponding polysilylated compounds 15-17 are prepared applying the mentioned methodology.
Asymmetric Synthesis of (3R,5R)- and (3S,5S)-2,6-Dimethylheptane-3,5-diol, useful C2 Chiral Auxiliaries
Jacoby, C.,Braekman, J.C.,Daloze, D.
, p. 753 - 756 (2007/10/02)
(R,R)- and (S,S)-2,6-Dimethylheptane-3,5-diol, which are useful C2 chiral auxiliaries, have been both synthesized in high optical purity from 2,6-dimethylheptane-3,5-dione, by using as key step a Sharpless kinetic resolution.
Chiral Organometallic Reagents, I. Stereoselective Exchange of Diastereotopic Bromine Atoms by Lithium in 1,1-Dibromo-3-(trimethylsilyloxy)alkanes
Hoffmann, Reinhard W.,Bewersdorf, Martin,Krueger, Michael,Mikolaiski, Wolfgang,Stuermer, Rainer
, p. 1243 - 1252 (2007/10/02)
Bromine-lithium exchange in 1,1-dibromo-3-(trimethylsilyloxy)alkanes 4 and 6 affords the carbenoids 8 and 14, which have been added to ketones, aldehydes, arylboronates, and silylating agents.Diastereoselectivity in the generation and trapping of the carb
Reduction of β-Hydroxy Ketones with Catecholborane. A Stereoselective Approach to the Synthesis of Syn 1,3-Diols
Evans, David A.,Hoveyda, Amir H.
, p. 5190 - 5192 (2007/10/02)
The stereoselective reduction of acyclic β-hydroxy ketones to syn 1,3-diols may be achieved with the mild reducing agent catecholborane.In certain instances reaction stereoselectivity may be enhanced through rhodium(I) catalysis.
Synthetically Useful β-Lithioalkoxides from Reductive Lithiation of Epoxides by Aromatic Radical Anions
Cohen, Theodore,Jeong, In-Howa,Mudryk, Boguslaw,Bhupathy, M.,Awad, Mohamed M. A.
, p. 1528 - 1536 (2007/10/02)
Epoxides are reductively cleaved by means of lithium 4,4'-di-tert-butylbiphenylide.Ethylene oxide itself cleaves to lithium 2-lithioethoxide (15) in less than 5 min at -95 deg C.Epoxides possessing one unsubstituted carbon atom reduce in a matter of minutes at -78 deg C.When both carbon atoms are monosubstituted, at least 1 h is required.Epoxides with one or with two geminal saturated substituents open mainly between the oxygen atom and the least substituted carbon atom.Ring opening in the other direction leads to an unstable β-lithioalkoxide which very rapidly forms an olefin.Acyclic 1,2-disubstituted epoxides yield only olefins.Cyclooctene oxide produces, after protonation, a 3:7 ratio of cyclooctanol and cyclooctene.Cyclohexene oxide gives a 3:1 ratio of cyclohexanol and cyclohexene.Vinyloxiranes, on the other hand, open at the most substituted C-O bond to produce an allylic anion associated with an alkoxide.The carbanionic centers of the resulting dianions add to the carbonyl groups of aldehydes and ketones; however, when a hydrogen atom is present on the carbon atom which is attached to both negatively charged atoms, some reduction of the carbonyl group competes with the nucleophilic addition.The allylic anions derived from vinyloxiranes, after treatment with titanium tetraisopropoxide or cerium(III) chloride, add to aldehydes mainly at the most or least substituted terminus, respectively.In the former case, the configuration of the resulting glycols is predominantly anti.A number of adducts of the dianions with conjugated unsaturated aldehydes and ketones can be converted to unsaturated cyclic 6-membered ring ethers in the presence of acid or methanesulfonyl chloride.
INTRAMOLECULAR HYDROSILYLATIONS II: THE ANTI-SELECTIVE REDUCTION OF β-HYDROXYKETONES
Anwar, S.,Davis, A.P.
, p. 3761 - 3770 (2007/10/02)
A study was made of the synthesis and intramolecular hydrosilylation of silyloxyketones (2) (Sheme 2).It was found that with a variety of Lewis acid catalysts, anti-selective hydrosilylation took place to give (3) and, after desilylation, (5).With SnCl4, the most effective and practical catalyst, ratios (3):(4) ranged between 40:1 and 120:1 for a number of substrates.An explanation for the stereoselectivity is proposed based on (Cl) as a transition state model.The result is an anti-selective reduction of β-hydroxyketones, summarised in Scheme 4.
