- Ni-catalysed, domino synthesis of tertiary alcohols from secondary alcohols
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The use of in situ generated (NHC)-Ni catalytic species (NHC = N-heterocyclic carbene) allows for the synthesis, in short reaction times, of a variety of tertiary alcohols from secondary alcohols through a domino oxidation-addition protocol.
- Berini, Christophe,Navarro, Oscar
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p. 1538 - 1540
(2012/02/16)
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- Ligand effects on diastereoselective addition of organocerium reagents to aldehydes and cyclic ketones
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A new class of chiral dialkoxy- and diaryloxyorganocerium reagent has been prepared and the diastereoselectivity of carbonyl addition reactions has been compared with that of conventional organocerium reagents.
- Greeves, Nicholas,Lyford, Lisa,Elizabeth Pease
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p. 285 - 288
(2007/10/02)
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- A Highly Stereoselective Synthesis of Trans-1,2-Disubstituted Cycloalkanols
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The study of the reactions of 1,4-bis(bromomagnesio)pentane, 1,1-bis(bromomagnesio)hexane, 1,4-bis(bromomagnesio)heptane, and 1,4-bis(bromomagnesio)octane with aliphatic and aromatic carboxylic acid esters in tetrahydrofuran solution was undertaken in order to ascertain which factors influence isomer distribution.The yields of this annelation processes are in the range of 68-88percent.The formation of trans OH 1,2-disubstituted cyclopentanols having the alkyl groups cis is generally observed with yields of 77-96percent.The reaction of 1,5-bis(bromomagnesio)hexane with carboxylicacid esters is less stereoselective and is more influenced by steric effects.
- Cannone, P.,Bernatchez, M.
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p. 4025 - 4031
(2007/10/02)
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- Stereoselective Addition of Organotitanium Reagents to Carbonyl Compounds
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Titanation of alkyllithium or -magnesium compounds using ClTi(OR)3 results in reagents which show markedly increased diastereofacial selectivity (80 - 90percent) in reactions with α-chiral aldehydes or ketones.Titanation is also the method of choice in Grignard-type additions to substituted cyclohexanones; CH3Ti(OCHMe2)3 (6a) adds predominantly from the equatorial direction, while allyltitanium reagents 11b and 12 show axial preference.Crotyltitanium compounds react with carbonyl compounds to afford primarily adducts having anti-configuration, a process which is of particular value in case of ketones (anti/syn ratios up to 99:1).Titanation of (trimethylsilyl)allyllithium (48) with Ti(OCHMe2)4 reverses regioselectivity in reactions with aldehydes and ketones, β-hydroxy silanes 50 being the only observed products.These have anti-configuration and can be converted either into Z- or E-dienes using the Peterson elimination under basic or acidic conditions, respectively.
- Reetz, Manfred T.,Steinbach, Rainer,Westermann, Juergen,Peter, Roland,Wenderoth, Bernd
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p. 1441 - 1454
(2007/10/02)
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