246257-67-0Relevant articles and documents
Cyclopropylamines from N,N-dialkylcarboxamides and grignard reagents in the presence of titanium tetraisopropoxide or methyltitanium triisopropoxide
De Meijere, Armin,Chaplinski, Vladimir,Winsel, Harald,Kordes, Markus,Stecker, Bjoern,Gazizova, Vesta,Savchenko, Andrei I.,Boese, Roland,Schill, Farina
, p. 13862 - 13875 (2011/03/18)
Thirty-three different N,N-dialkyl- and N-alkyl-N-phosphorylalkyl- substituted carboxamides 9-17 were treated with unsubstituted as well as with 2-alkyl-, 2,2-dialkyl-, and 3-alkenyl-substituted ethylmagnesium bromides 6 in the presence of stoichiometric amounts of titanium tetraisopropoxide or methyltitanium triisopropoxide to furnish substituted cyclopropylamines 20-25 in 20-98 % yield, depending on the substituents with no (1:1) to excellent (>25:1) diastereoselectivities. Generally higher yields (up to 98 %) of the cyclopropylamines 20-28 without loss of the diastereoselectivity were obtained with methyltitanium triisopropoxide as the titanium mediator. Under these conditions, even dioxolane-protected ketones and halogen-substituted and chiral as well as achiral alkyloxyalkyl-substituted carboxamides could be converted to the correspondingly substituted cyclopropylamines with unsubstituted as well as phenyl- and a variety of alkyl-substituted ethylmagnesium bromides in addition to numerous heteroatom-containing (e.g., halogen-, trityloxy-, tetrahydropyranyloxy-substituted) Grignard reagents (62 examples altogether). The transformation of N,N-diformylalkylamines 54 with ethylmagnesium bromide in the presence of methyltitanium triisopropoxide to N,N-dicyclopropyl-N- alkylamines 55 can be brought about in up to 82 % yield (6 examples). An asymmetric variant of the titanium-mediated cyclopropanation of N,N-dialkylcarboxamides has been developed by applying chiral titanium mediators generated from stoichiometric amounts of titanium tetraisopropoxide and chiral diamino or diol ligands, respectively. The most efficient chiral mediators turned out to be titanium bistaddolates that provided the corresponding cyclopropylamines with enantiomeric excesses (ee) of up to 84 %. Evaluation of several silyl-based additives revealed that the reaction can also efficiently be carried out with substoichiometric amounts (down to 25 Mol %) of the titanium reagent, as long as 2-aryl- or 2-ethenyl-substituted ethylmagnesium halides are used and a concomitant slight decrease in yields is accepted. The newly developed methodology was successfully applied for the preparation of analogues with cyclopropylamine moieties of known drugs and natural products such as the nicotine metabolite (S)-Cotinine as well as the insecticides Dinotefuran and Imidacloprid. Ti is it: Cyclopropylamines have been obtained in low to excellent yield through the reaction of different N,N-dialkyl- and N-alkyl-N- phosphorylalkyl-substituted carboxamides with Grignard reagents in the presence of stoichiometric amounts of titanium tetraisopropoxide or methyltitanium triisopropoxide (see scheme). Copyright
Radical cations of trialkylamines: ESR spectra and structures
De Meijere, Armin,Chaplinski, Vladimir,Gerson, Fabian,Merstetter, Pascal,Haselbach, Edwin
, p. 6951 - 6959 (2007/10/03)
Novel syntheses of cyclopropyldiisopropylamine (15), di-tert- butylcyclopropylamine (16), dicyclopropylisopropylamine (17), and tricyclopropylamine (18) are described. Hyperfine data were determined by ESR spectroscopy for the radical cations of these trialkylamines, as well as for those of ethyldiisopropylamine (10), diisopropyl-n-propylamine (11), dicyclohexylethylamine (12), diisopropyl-3-pentylamine (14), and 1- azabicyclo[3.3.3]undecane (manxine; 27). The radical cation of triisopropylamine (13) was reexamined under conditions of improved spectral resolution. Coupling constants of the 14N nucleus and the β-protons in the radical cations of 18 trialkylamines provide reliable information about the geometries of these species, which are confirmed by theoretical calculations. With the exception of a few oligocyclic amines, for which flattening is impaired by the rigid molecular framework, all of the radical cations should be planar. Correlation between the observed coupling constants of the β- protons and the calculated 2 θ> values of the dihedral angle θ, defining the conformation of the alkyl substituent or the azacycloalkane, is verified. Upon oxidation, striking changes occur for those amines that have cyclopropyl substituents, because of the tendency of these groups to assume a perpendicular conformation in the neutral amines and a bisected orientation in the corresponding radical cations.
