Terminal-Selective Functionalization of Alkyl Chains by Regioconvergent Cross-Coupling
Hydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C?H bond functionalization methods. We describe herein a new step-economical approach that enables C?C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross-coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross-coupling then provided access to the corresponding linear arylation product in only two steps.
Iron-catalyzed alkylations of aromatic Grignard reagents
(Chemical Equation Presented) Any old iron: Two efficient iron-catalyzed cross-coupling reactions between aryl Grignard reagents and alkyl bromides were developed that are suitable for large-scale applications. The first procedure uses iron acetylacetonate and involves a cooperative effect between the two ligands N,N,N′,N′-tetramethylethylenediamine (TMEDA) and hexamethylenetetraamine (HMTA), while the second procedure uses [(FeCl 3)2(tmeda)3] as catalyst. 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
Cahiez, Gerard,Habiak, Vanessa,Duplais, Christophe,Moyeux, Alban
p. 4364 - 4366
(2008/03/12)
The action of sodium hydrogen telluride on olefins
The action of sodium hydrogen telluride, NaTeH, on non electrophilic carbon-arbon double bonds has been investigated.The reaction is found to be very sensitive to the substituents on the ethylenic linkage. Whereas phenyl conjugated olefins are reduced to alkylbenzenes,the reagent adds to isolated mono and disubstituted double bonds leading to organotellurium derivatives and with gem-disubstituted ones it leads to a mixture of reduction and addition products. These results are interpreted in terms of a radical pair mechanism involving hydrogen atom transfer from hydrogen telluride,HTe- to the double bond.
Barton, Derek H. R.,Bohe, Luis,Lusinchi, Xavier
p. 5273 - 5284
(2007/10/02)
SODIUM HYDROGEN TELLURIDE: A MECHANISTIC CHAMELEON
Relative rates of reduction of several α,β-unsaturated esters and styrenes added to recently obtained results from other substrates show that sodium hydrogen telluride (NaTeH) can react according to different mechanisms : nucleophilic substitution, hydride transfer, hydrogen atom transfer and electron transfer.
Barton, Derek H. R.,Bohe, Luis,Lusinchi, Xavier
p. 6609 - 6612
(2007/10/02)
Structures and pesticidal activities of derivatives of dinitro-phenols. IV. Preparation of certain 2-(alpha-branched alkyl)-4,6-dinitro- and 4-(alpha-branched alkyl)-2,6-dinitro-phenols.
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Pianka,Edwards
p. 2281 - 2290
(2007/10/05)
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