Mathias Noltemeyer

A Catalytic Enantioselective Electron Transfer Reaction: Titanocene-Catalyzed Enantioselective Formation of Radicals from meso-Epoxides.

A rationally designed titanium(III) catalyst allows the opening of epoxides with high enantioselectivity. This reaction [Eq. (1)] constitutes the first example of an enantioselective transition metal catalyzed radical reaction that proceeds by electron transfer.

Organoactinoid-Komplexe : Substituierte Benzamidinat-Anionen als sterische Äquivalente zu η5-C5H5 und η5-C5Me5. Molekülstrukturen von [PhC(NSiMe3)2]3UCl, [4-CF3C6H4C(NSiMe3)2]3UCl, [2,4,6-(CF3)3C6H2C(NSiMe3)2]2UCl2 und [2,4,6-(CF3)3C6H2C(NSiMe3)2]2ThCl2

The reaction of substituted benzonitrile derivatives with LiN(SiMe3)2 or NaN(SiMe3)2 yields N,N′-bis(trimethylsilyl)benzamidinates Li[RC6H4C(NSiMe3)2] (1) and Na[RC6H4C(NSiMe3)2] (2) (R = H, Me, OMe, CF3) respectively. 2,4,6-Trisubstituted derivatives, Li[R3C6H2C(NSiMe3)2] (3: R = CF3, 4: R = Me) are available by addition of R3C6H2Li to Me3SiNCNSiMe3. The N,N′-bis(trimethylsilyl)benzamidinate anions can be regarded as steric equivalents of η5-C5H5 and η5-C5Me5. The alkali metal derivatives 1 and 2 react with UCl4 to give substituted benzamidinato-uranium(IV) chlorides. Depending on the stoichiometry, complexes of the type [RC6H4C(NSiMe3)2]2UCl2 (5) and [RC6H4C(NSiMe3)2]3UCl (6) can be isolated. Sterically more demanding ligands [R3C6H2C(NSiMe3)2]− give exclusively the disubstituted products [R3C6H2C(NSiMe3)2]2UCl2 (7: R = CF3, 8: R = Me). The thorium(IV) complexes [(CF3)3C6H2C(NSiMe3)2]2ThCl2 (9) and [CF3C6H4C(NSiMe3)2]3ThCl (10) can similarly by synthesized. The structures of [PhC(NSiMe3)2]3UCl (6a), [4-CF3C6H4C(NSiMe3)2]3UCl (6d), [2,4,6-(CF3)3C6H2C(NSiMe3)2]2UCl2 (7) and [2,4,6-(CF3)3C6H2C(NSiMe3)2]2ThCl2 (9) were determined by X-ray crystallography.

Metallocene analogues containing bulky heteroallylic ligands and their use as new olefin polymerization catalysts

Abstract A series of Ti and Zr metallocene analogues containing bulky benzamidinate ligands has been prepared and fully characterized. Treatment of TiCl 4 (THF) 2 or ZrCl 4 (THF) 2 with two equivalents of the appropriate benzamidinate anions affords the bis(benzamidinato) complexes [C 6 H 5 C(NC 3 H 7 ) 2 ] 2 MCl 2 (M=Ti ( 1 ), Zr ( 2 )) and [C 6 H 5 C(NC 6 H 11 ) 2 ] 2 MCl 2 (M=Ti ( 3 ), Zr ( 4 )). The zirconium complex 2 was structurally characterized by X-ray diffraction. In a similar manner the nonafluoromesityl derivative [(CF 3 ) 3 C 6 H 2 C(NC 6 H 11 ) 2 ] 2 ZrCl 2 ( 5 ) was synthesized from ZrCl 4 (THF) 2 and Li[(CF 3 ) 3 C 6 H 2 C(NC 6 H 11 ) 2 ]. Methylation of 4 with methyllithium yields the dimethyl complex [C 6 H 5 C(NC 6 H 11 ) 2 ] 2 ZrMe 2 ( 6 ). The mixed-ligand metallocene analogues [C 6 H 5 C(NC 3 H 7 ) 2 ](C 5 Me 5 )MCl 2 (M=Ti ( 7 ), Zr ( 8 )) and [C 6 H 5 C(NC 6 H 11 ) 2 ](C 5 Me 5 )TiCl 2 ( 9 ) have been prepared by reacting (C 5 Me 5 )TiCl 3 or (C 5 Me 5 )ZrCl 3 with one equivalent of a lithium N , N ″-dialkylbenzamidinate. The polymerization of ethylene and propylene has been studied by the catalytic precatalyst complexes 1 and 2 upon reaction of an excess of methylalumoxane to obtain the active cationic complexes. The polymerization activity of the complexes is comparable to other benzamidinate ancillary containing ligands although toward shorter amounts of time due to a competitive inhibition presumably obtained by a β -hydrogen elimination from the ligand. Polymerization activity is strongly dependent on catalyst and cocatalyst concentrations and on temperature.

A new inorganic metallocycle containing tin, sulphur, phosphorus and nitrogen. Crystal and molecular structure of spirobicyclic Me2Sn(SPPh2NPPh2S)2

Abstract A new inorganic heterocycle is obtained by reacting potassium tetraphenyldithioimidodiphosphinate with trimethyltin and dimethyltin chlorides, in benzene. X-ray diffraction analysis reveals a spirocyclic structure with the dimethyltin moiety as the coordination centre with non-planar six-membered SnS 2 P 2 N rings. The coordination at tin is nearly perfectly octahedral, with equal SnS [273.3(2) and 273.7(2) pm] and PS bonds [200.9(3) and 201.9(3) pm]. The SSnS and H 3 CSnCH 3 units are co-linear.

[Zn2(thf)2(EtZn)6Zn4(μ4‐O)(tBuPO3)8]: A Dodecanuclear Zincophosphonate Aggregate with a Zn4(μ4‐O) Core

The largest multinuclear zinc framework synthesized is in the title compound (see picture), which contains structural features closely related to the motifs found in layered and three-dimensional zincophosphates and zincophosphonates. The reactive centers make this zincophosphonate a viable precursor for the synthesis of porous zincophosphonate materials.

Mono- and Disubstituted N,N-Dialkylcyclopropylamines from Dialkylformamides via Ligand-Exchanged Titanium–Alkene Complexes†

Dibenzylformamide was treated with cyclohexylmagnesium bromide in the presence of either titanium tetraisopropoxide or methyltitanium triisopropoxide and a variety of cyclic and acyclic alkenes and alkadienes to give new mono- and disubstituted as well as bicyclic dialkylcyclopropylamines (Tables 1–3, 2, 3) in yields ranging from 18 to 90 % (in most cases around 55 %). 3-Benzyl-6-(N,N-dibenzylamino)-3-azabicyclo[3.1.0]hexane (10 a) and the orthogonally bisprotected 3-tert-butoxycarbonyl-6-(N,N-dibenzyl)-3-azabicyclo[3.1.0]hexane (10 d) as well as the analogous 6-(N,N-dibenzylamino)bicyclo[3.1.0]hexane (12) were obtained as pure exo diastereomers in particularly high yields (87, 90, and 88 %, respectively) from N-benzylpyrroline (15 a), N-Boc-pyrroline (15 d; Boc=tert-butyloxycarbonyl) and cyclopentene (19). 1,3-Butadiene (52) and substituted 1,3-butadienes were also aminocyclopropanated quite well to give 2-ethenylcyclopropylamines in good yields (51–64 %). Except for alkenyl- and aryl-substituted compounds, N,N-dibenzylcyclopropylamines can be debenzylated by catalytic hydrogenation to the primary cyclopropylamines as demonstrated for 10 a and 10 d to yield the fully deprotected 10 e (93 %) and mono-Boc-protected 10 f (98 %), respectively. The latter are interesting templates for combinatorial syntheses of libraries of small molecules with a well defined distance of 4.3 A between two nitrogen atoms.

Organolanthanid(II)chemie: Reaktionen von CP 2 Sm(THF)2 mit 1,4-diazadienen und cyclooctatetraen

Abstract Cp★ 2 SM(THF) 2 reacts with 1,4-diazadienes (DAD) to give 1:1-adducts of the type Cp★ 2 Sm(DAD). The molecular structure of Cp★ 2 Sm( t BuNCHCHN t Bu) ( 2 ) has been determined by X-ray crystallography. These complexes can be described as Cp★ 2 Sm III derivatives of the diazadiene radical anions as indicated by spectroscopic and structural data. Treatment of Cp★ 2 Sm(THF) 2 with 2-pyridinealdazine yields the binuclear complex (μ-C 12 H 10 N 4 )[Cp★ 2 Sm] 2 ( 5 ). Cyclooctatetraene reacts with Cp★ 2 Sm(THF) 2 to give the known compound Cp★Sm(COT)(THF) ( 6 ).

A new highly efficient three-component domino Heck-Diels-Alder reaction with bicyclopropylidene: rapid access to spiro[2.5]oct-4-ene derivatives.

Bicyclopropylidene (1) was found to surpass even methyl acrylate (17 a) in its rate of undergoing carbopalladation with aryl- or alkenylpalladium species, leading to substituted allylidenecyclopropanes 5, 7 and 10, mostly in high yields (37-78 %). These dienes and cross-conjugated trienes react in a Diels-Alder mode with dienophiles to give spiro[2.5]octenes 18 a-Ph, 18 b-Ph and 18 a-Vin, respectively, in good yields (89, 69 and 65 %). The overall transformation can be achieved as a one-pot three-component reaction with a variety of dienophiles to furnish the domino Heck-Diels-Alder products 18 regioselectively in most cases in good to very high yields (49-100 %). The reaction of 1 with iodobenzene (2-Ph) and 17 a gave 18 a-Ph in virtually quantitative yield-also on a gram scale-using only 1 mol % of catalyst, and even bromobenzene (22) gave 18 a-Ph in 59 % yield. Bicyclopropylidene (1), in the presence of palladium acetate/triphenylphosphane underwent rearrangement to allylidenecyclopropane (5-H), which in turn dimerized (73 %) in the absence of other reaction partners, or could be trapped by diethyl fumarate (17 c) to give the Diels-Alder adduct 18 c-H in 45 % yield. The coupling of oligoiodobenzenes with 1 and subsequent cycloaddition could be extended to a multicomponent reaction. In this way, 1,4-diiodobenzene (37), 1 and an alkyl acrylate gave the products 38 of a twofold Heck-Diels-Alder reaction in up to 87 % yield, 1,3,5-triiodobenzene (39) reacted in up to 72 % yield and ultimately 1,2,4,5-tetraiodobenzene (41) gave the fourfold domino Heck-Diels-Alder product 42 in 47 % isolated yield, in a single operation in which 12 new carbon-carbon bonds were formed.

Intramolecular Diels-Alder reactions of furans with a merely strain-activated tetrasubstituted alkene: Bicyclopropylidene

Bicyclopropylidene derivatives 1, 6, 8 with furan moieties attached on tethers of various length and nature all undergo clean intramolecular Diels-Alder reactions with complete endo-diastereoselectivities when heated to 70 – 130°C, under 10 kbar pressure. The reaction rates are at least as high or higher than those of analogously tethered methylenecyclopropane-furan derivatives 15, 17, 20, in spite of the fact that the reactive double bond in bicyclopropylidene is tetrasubstituted and not activated by any electron withdrawing group.

Diiminophosphinate des Lithiums, Samariums und Ytterbiums: Moleku¨lstrukturen von Li[Ph2P(NSiMe3)2](THF)2 und [Ph2P(NSiMe3)2]2Sm(μ-I)2Li(THF)2

Abstract The molecular structure of Li[Ph2P(NSiMe3)2](THF)2 (2) has been determined by an X-ray diffraction study. A four-membered LiNPN ring forms the central unit of the monomeric molecule. YbI2 reacts with two equivalents of Li[Ph2P(NSiMe3)2] (1) to give the novel ytterbium(II)diiminophosphinate [Ph2P(NSiMe3)2]2Yb(THF)2 (3). A similar reaction of 1 with SmI2 affords the samarium(III) derivative [Ph2P(NSiMe3)2]2Sm(μ-I)2Li(THF)2 (4) whose structure has also been determined by an X-ray diffraction study.