Jens Kaufmann

Palladium-catalyzed cross-methylation of aryl triflates by intramolecularly stabilized dialkyl-aluminum, -gallium and -indium reagents

Abstract Several phenyl and naphthyl triflates undergo catalytic cross-methylation with the monomeric and dimeric dimethyl-aluminum, -gallium and -indium complexes 1a , 1b , 1c , 3a , 3b and 3c in the presence of either PdCl 2 (PPh 3 ) 2 , Pd(PPh 3 ) 4 or Pd(binap)(OAc) 2 . 4-Bromophenyl triflate reacts selectively via the triflate function. Structural features of the substrate and the methylating agent, as well as the nature and quality of the palladium catalyst have a considerable influence on the cross-coupling process.

Diallylaluminium-N,N-dimethylaminoethanolate, the first stable allyl-alane suitable for additions to aldehydes, ketones and imines

Abstract The reaction of AlCl 3 with lithium- N , N -dimethylaminoethanolate ( 3 ) in a 1:1 ratio yields the corresponding organo-aluminium chloride [Cl 2 Al(μ-OCH 2 CH 2 NMe 2 )] 2 ( 1 ) from which the diallyl derivative [(CH 2 CHCH 2 ) 2 Al(μ-OCH 2 CH 2 NMe 2 )] 2 ( 4 ) was synthesized by treatment with 2 equiv. of allyl magnesium bromide. The structures of 1 and 4 were deduced from the 1 H, 13 C, 27 Al NMR spectra and confirmed by X-ray structural determination. The allyl aluminium complex 4 was found to be a useful reagent for the transfer of one allyl group to aldehydes, imines and enones. The 1,2-addition products are formed in high yields.

[(CH2CH)2Al(μ-OCH2CH2NMe2)]2: a vinylalane reagent suitable for conjugate additions to α,β-unsaturated ketones

Abstract The reaction of AlCl3 with 2-dimethylaminoethanol in a 1:1 mole ratio yields [Cl2Al(μ-OCH2CH2NMe2)]2 ( 1 ), which further reacts with two equivalents of vinylmagnesium chloride to give the divinylalane [(CH2CH)2Al(μ-OCH2CH2NMe2)]2 ( 2 ). Compound 2 was characterized by elemental analysis, 1H, 13C, and 27Al NMR spectra, mass spectrum and by X-ray structural analysis. Compound 2 was found to be a useful reagent for the transfer of a vinyl group to 1,3-diphenyl-2-propene-1-one (trans-chalcone). The 1,4-addition product is formed regioselectively, both in a non-catalyzed as well as in a nickel-catalyzed reaction.

Synthesis and Characterization of Intramolecularly Stabilized Chiral Dimethylindium Alkoxides and their Use as Cross Coupling Reagents

The enantiomerically pure dimeric N, O-5-chelates [Me2In(μ-OCH2CH(R)NMe2)]2 {R = Me (S) (2); R = iPr (S) (3); R = iBu (S) (4); R = Bz (S) (5)}, and [Me2In-{μ-(1R, 2S)-OCH(Ph)CH(Me)NMe2}]2 (6), as well as the achiral dimeric N, O-6-chelate [Me2In(μ-O(CH2)3NMe2)]2 (7) have been synthesized from trimethylindium and equimolar amounts of the corresponding enantiomerically pure dimethylamino alcohols or of the achiral dimethylaminopropanol by elimination of methane. Their 1H NMR, 13C NMR, and mass spectra as well as the X-ray single crystal structure analyses of [Me2In{μ-O(CH2)2NMe2}]2 (1), 3, 5, 6 and 7 are described and discussed. The coordinative NIn bonds of the five-coordinate indium complexes show dynamic dissociation/association processes. 1—6 were found to be useful reagents for the partial kinetic resolution of 2-carbomethoxy-1, 1′-binaphthyl triflate. Synthese und Charakterisierung intramolekular stabilisierter chiraler Dimethylindiumalkoxide und deren Verwendung als Kreuz-Kupplungs-Reagentien Die enantiomerenreinen dimeren N, O-5-Chelate [Me2In(μ-OCH2CH(R)NMe2)]2 {R = Me (S) (2); R = iPr (S) (3); R = iBu (S) (4); R = Bz (S) (5)}, und [Me2In-{μ-(1R, 2S)-OCH(Ph)CH(Me)NMe2}]2 (6), sowie das achirale dimere N, O-6-Chelat [Me2In(μ-O(CH2)3NMe2)]2 (7) werden aus Trimethylindium und equimolaren Mengen der enstsprechenden enantiomerenreinen Dimethylaminoalkohole bzw. von achiralem Dimethylaminopropanol unter Methan-Abspaltung erhalten. Die 1H-NMR, 13C-NMR und Massenspektren sowie die Rontgenstrukturanalysen von [Me2In{μ-O(CH2)2NMe2}]2 (1), 3, 5, 6 und 7 werden diskutiert. Die koordinativen NIn-Bindungen der funffach koordinierten Indium Komplexe zeigen in Losung ein dynamisches Dissoziation/Assoziations Verhalten. 1—6 eignen sich als Reagentien fur die kinetische Enantiomerentrennung von 2-Carbomethoxy-1, 1′-binaphthyltriflat.