Bisaminophosphane – Synthese,Struktur und Reaktivität

Bisaminophosphanes – Synthesis, Structure, and Reactivity Different pathways for the synthesis of bis(alkylamino)phosphanes RP(N(H)R′)₂ are described. t‐BuP(N(H)‐ Dipp)₂ (Dipp = 2,6‐i‐Pr₂–C₆H₃) was structurally characterized by single crystal X‐ray diffraction. The reactivity of the compounds was examplarily investigated using t‐BuP(N(H)t‐Bu)₂. Its reaction with Me₃Al and R₂AlH (R = Me, Et, i‐Bu) in 1 : 1 and 1 : 2 stoichiometrie yield monosubstituted compounds of the type t‐BuP(N(H)t‐Bu)(N(AlR₂)t‐Bu).     

Vergleich der Reaktivität von Triethyltrithiophosphit und Trialkylphosphit bei der Synthese von P?N-Verbindungen

Comparison of the Reactivity of Triethyl Phosphorotrithioite and Triethylphosphite by Synthesis of P? N Compounds Triethyl phosphorotrithioite, (EtS)₃P, reacts unlike triethylphosphite with carbon tetrachloride and nitrogen containing nucleophiles. No reaction occurs with diester amides of phosphoric acid. When (EtS)₃P is allowed to react with primary aliphatic amines not amides of phosphoric acid are obtained, but (EtS)₂PCCl₃ and EtSNHEt are yielded. In the reaction of (EtS)₃P with (EtO)₂P(O)H, CCl₄, and NaN₃ results the expected monophosphazene (EtO)₂P(O)? N?P(SEt)₃ only. The different nucleophilicity of phosphorus in (EtS)₂P and (EtO)₃P follows from CNDO/2-MO calculations, too.     

Zum Zusammenhang zwischen Ligand-Acidität und Metallkomplex-Stabilität: Abnehmende Stabilität bei zunehmender Basizität

The increase of the stability of metal ion complexes with decreasing basicity of the ligands within different series is discussed with the help of the equation of IRVING & ROSSOTTI [4] [12] and explained in terms of the free energy G of the complexes.     

Synthesis und Reaktivität von Dimethylaminoalkylidenaminooxy-arsinen

Synthesis and Reactivity of Dimethylaminoalkylideneaminooxiarsines The reactions of As[N(CH₃)₂]₃ with oximes result in the formation of the oximates [(CH₃)₂N]₂AsONCRR′, (CH₃)₂N As(ONCRR′)₂ and As(ONCRR′)₃. The eleavage of the As-N-bond with alcohols, thiols and diols are described. The reactions of CH₃As[N(CH₃)₂]ONCRR′ with water, amine and alcohols are examined. IR-and ¹H-NMR-spectral data are presented.     

Stereoselektivität und Reaktivität bei der 1,3-dipolaren Cycloaddition chiraler N-(Alkoxyalkyl)nitrone

Stereoselectivity and Reactivity in the 1,3-Dipolar Cycloaddition of Chiral N-(Alkoxyalkyl)nitrones The stereoselectivity in the reaction of hydroxy-oxime 1 with acetaldehyde and methyl methacrylate yielding the diastereomeric isoxazolidine-ribosides 9–12 was determined to be 93%. The predominant adducts 9 and 10 were cleaved to the diastereomeric isoxazolidines 19 and 20 , respectively, which upon oxidation gave the same optically active 2-isoxazoline 21 , thus demonstrating the participation in the cycloaddition of both (E/Z)-isomeric nitrones 13 and 14 . Based upon comparison of the optical rotations, the isoxazolidines 7 , 8 , 19 and 20 and the 2-isoxazolines 21 and 22 possess the same chirality, found to be R by correlating 7 with (+)-(S)-citramalic acid. - Since the hydroxy-oximes 1 and 36 showed the same stereo-selectivity in the reaction with formaldehyde and methyl methacrylate, the trityl group of 1 does not influence the stereoselectivity in the cycloaddition. The hydroxyoxime 38 led in the same type of reaction to the isoxazolidines 7 , 8 , 19 and 20 possessing (S)-chirality, the stereoselectivity (79–95%) being similar to the one observed with 1 (67–95%). The explanation of this stereoselectivity is based upon a stereoelectronic effect in the transition state of the cycloadditions (kinetic anomeric effect). As predicted, the N-(alkoxyalkyl)nitrones showed enhanced reactivity in the cycloaddition with unactivated olefins (leading to 47 , 48 , 50 and 51 ). The importance of exo vs. endo approach of the dipolarophile was evidenced by reacting 1 with formaldehyde and methyl acrylate giving predominantly 57 with (5S)-configuration. - Use of the hydroxy-oxime 65 allows synthesis of optically active isoxazolidines with regeneration of the starting hydroxy-oxime.