Johann T. B. H. Jastrzebski

Selective hydrovinylation of styrene in a membrane reactor : use of carbosilane dendrimers with hemilabile P,O ligands

A codimerization of styrene and ethene can be carried out continuously in a nanofiltration membrane reactor with dendritic Pd complexes such as 1. The selectivity of the reaction is increased considerably under continuous conditions. The activity and selectivity of monomeric model complexes and the dendritic catalysts were compared in batch reactions.

Application of N,S-chelating chiral zinc bis(arenethiolate) complexes as new precursor catalysts in the enantioselective addition of diethylzinc to aldehydes

Abstract The addition of diethylzinc to aldehydes in the presence of a catalytic amount of enantiomerically pure N,S -chelated bis {2-[( R )-1-(dimethylamino)ethyl]phenylthiolato}zinc, afforded the corresponding secondary alcohols in nearly quantitative yields with optical purities of up to 99 % e.e. under mild reaction conditions.

Novel tridentate diamino organomanganese(II) complexes as homogeneous catalysts in manganese(II):copper(I) catalyzed carbon-carbon bond forming reactions

The new, paramagnetic arylmanganese(II) complex Li[MnCl2(NCN)] (2, NCN [C6H3(CH2NMe2)2-2,6]) has been obtained in high yield from the reaction of MnCl2 and [Li(NCN)]2 in a 2:1 molar ratio. In THF solution, 2 is likely an ionic species [Li(THF)n] [MnCl2(NCN)] (molecular weight determination and conductivity measurements), while magnetic measurements indicate that a high spin d 5 manganese(II) center is present. Subsequent reaction of 2 with RLi afforded [MnR(NCN)] (R Me (3a), n-Bu (3b)). Complex 2, using CuCl as a co-catalyst, is an effective catalyst system for cross-coupling of Grignard reagents with alkyl bromides and the 1,4-addition of organomagnesium halides to a,b-unsaturated ketones. No further additives or co-solvents are necessary. For both reactions a dramatic decrease in reaction times is observed when compared to standard manganese:copper systems. Alkyl bromides with unsaturated or heteroatom functionalities can be cross-coupled. Also, excellent reactivity towards normally unreactive b,b-disubstituted ketones has been observed in the 1,4-addition reaction.

Synthesis and characterization of a stable bis-naphthyltin(II) compound.Bis[8-(dimethylamino)-1-naphthyl-C,N]tin(II) and its W(CO)5 adduct

Reaction of [8-(dimethylamino)-1-naphthyl-C, N]lithium with SnCl{2} affords the new monomeric stannylene bis[8-(dimethylamino)-1-naphthyl-C,N]tin(II) (3). The reaction between W(CO){5}(NME{3}) and 3 yields {bis[8-(dimethylamino)-1-naphthyl-C,N]tin(II)} tungsten pentacarbonyl (4). The crystal structures of 3 and 4 have been determined by X-ray diffraction methods. 3: C{2}{4}H{2}{4}N{2}Sn, orthorhombic, space group Pbca with a 22.383(4), b 30.865(5), c 12.127(2) @9 and Z = 16, final R = 0.067 for 4983 observed reflections. 4: C{2}{9}H{2}{4}N{2}O{5}SnW, a 12.509(3), b 15.191(1), c 9.780(1) @9, @a 98.42(1), @b 104.33(1), @c 107.27(1)}o{, space group P1, Z = 2, triclinic; R = 0.046 for 7116 observed reflections. The geometry about tin in 3 is distorted @j-trigonal bypyramidal, and that in 4 is distorted trigonal bipyramidal. In both 3 and 4 the 8-(dimethylamino)-1-naphthyl groups are C,N-chelate bonded, with the C(1) atoms at equatorial sites and the nitrogen atoms at axial sites. The Sn lone pair in 3 and the W(CO){5} moiety in 4 occupy the remaining equatorial sites. }1{H, }1{}3{C, and }1{}1{}9{Sn solution NMR spectroscopic studies of 3 and 4 show that at low temperature (=< - 15}o{C) they retain the structures found in the solid state. At higher temperatures fluxional processes become operative.

Oxidative-addition reactions of molecular diiodine and dibromine to divalent organotin compounds. Crystal structures of bis(8-( dimethylamino)-1-naphthyl)tin( IV) dibromide and { 2,6-(bis( dimethylamino)methyl)phenyl} - (4-tolyl) tin( IV) diodide

Abstract The reactions of bis[8-(dimethylamino)-1-naphthyl]tin(II) with dibromine or diiodine afford bis[8-(dimethylamino)-1-naphthyl]tin(IV) dibromide ( 1 ) and bis[8-(dimethylamino)-1-naphthyl]tin(IV) diiodide ( 2 ), respectively. Reaction of {2,6-[bis(dimethylamino)methyl]phenyl}(4-tolyl)tin(II) with diiodine gives {2,6-[bis(dimethylamino)Methyphenyl}(4-tolyl)tin(IV) diiodide ( 3 ) in quantitative yield. The crystal structures of 1 and 3 have been determined by X-ray diffraction methods. As a result of intramolecular coordination of the nitrogen atoms with the tin centers, the geometry about tin in both 1 and 3 is octahedral, while the carbon atoms bound to tin are in trans position. In 1 the two bromine atoms are cis to one another, as are the two nitrogen atoms, whereas in 3 the two iodine atoms, like the two nitrogen atoms, are trans to one another. 1 H, 13 C and 119 Sn solution NMR spectroscopic studies of 1–3 show that they retain the structures found in the solid state.

Stereoselective one-pot syntheses of trans-3-amino-β-lactams from zinc enolates of N-protected α-aminoacid esters and imines

A new one-pot synthesis of 3-amino@b-lactams that is based on the condensation of simple imines with zinc enolates of disilyl protected glycine esters is reported. Isolated yields are high and a trans-selectivity is observed.

Synthesis and catalytic application of amino acid based dendritic macromolecules

The use of amino acid based dendrimers as molecular scaffolds for the attachment of catalytically active organometallic Ni “pincer” complexes, via a urea functionality, is described; the dendrimer catalysts have comparable activity to their mononuclear (NCN)NiX analogues.

Organotin(IV) compounds 2-(Me2NCHR)C6H4(SnR′R″Br) with a fixed s-cis arrangement of the chiral carbon and tin centers. Crystal structure of 2-(Me2NCHBut)C6H4SnMePhBr

Abstract A series of novel pentacoordinate triorganotin bromides SnR′R″Br[C 6 H 4 CH(R)NMe 2 -2] have been synthesized and characterized in which R is H, Me, Et, i-Pr or t-Bu. The crystal structure of one of these compounds (R = t-Bu, R′ = Me and R″ = Ph) has been determined. The tin center has a distored trigonal-bipyramidal coordination geometry. The organic ligands occupy the equatorial sites, while the more electronegative Br and N ligands are in the axial positions. As a requirement of the space group symmetry the unit cell contains 8 enantiomeric pairs of diastereoisomers ( R ) C ( S ) Sn and ( S ) C ( R ) Sn . The given configuration at the chiral benzylic carbon atom is combined with a configuration at the chiral tin atom in such a way that the sterically most favorable diastereoisomer is formed. The influence of the steric requirements of the ortho -substituent Z = HRNMe 2 in 2-ZC 6 H 4 (SnRR′Br) on the configuration of the Sn center has been studied. These compounds contain a fixed s-cis Z-C-C-Sn orientation. 1 H and 119 Sn NMR spectroscopic studies show that in solution at low temperatures (−25°C) all these compounds are pentacoordinate as a result of intramolecular coordination. At higher temperatures a fluxional process becomes operative involving Sn-N bond dissociation/association. However, even at +110°C the Sn center is configurationally stable on the NMR time scale. For the compounds in which the Sn atom is also a chiral center (R′ = Me and R″ = Ph) in solution there is an equilibrium between two diastereoisomers, the ratio being dependent on the bulk of the benzylic substituent R. For R = t-Bu the equilibrium lies completely to the side of the sterically most favorable one.

Selektive Hydrovinylierung von Styrol im Membranreaktor: Anwendung von Carbosilandendrimeren mit hemilabilen P,O-Liganden

Kontinuierlich kann die Codimerisierung von Styrol und Ethen mit dendritischen Pd-Komplexen wie 1 in einem Nanofiltrations-Membranreaktor durchgefuhrt werden. Die Selektivitat der Reaktion wird unter kontinuierlichen Bedingungen deutlich erhoht. Monomere Modellkomplexe und dendritische Katalysatoren werden im Satzbetrieb hinsichtlich Aktivitat und Selektivitat verglichen.

Formation of mixed aryl-, alkyl-lithium aggregates in the heteroatom assisted lithiation of a,a'-dialkyl substituted 1,3-bis[(dimethylamino)methyl]benzene

Abstract The heteroatom assisted lithiation of 1,3-bis[1-(dimethylamino)ethyl]benzene with n-BuLi afforded 2,6-bis[1-(dimethylamino)ethyl]phenyllithium. An X-ray crystal structure determination revealed a dimeric aggregate in which the four benzylic chiral centers are identical, pointing to stereoselective crystallization. In contrast, reaction of 1,3-bis[1-(dimethylamino)propyl]benzene with n-BuLi afforded a dimeric aggregate comprising the parent lithiated compound and n-BuLi in a 1:1 molar ratio. The four Li atoms and the four bridging carbon atoms are arranged in a unique ladder-type C–Li2–C2′–Li2–C framework.