Synthesis of Arylzinc Thiolates Containing Perfluoroalkyl Chains : Model Catalyst Precursors for the Enantioselective Zinc-Mediated 1,2-Addition of Dialkylzincs to Aldehydes in Fluorous Biphase Systems

The synthesis of perfluoroalkyl-functionalized arene trimethylsilyl ethers and their conversion to ethylzinc thiolates is described. These compounds have been successfully applied as catalysts in the enantioselective addition of diethylzinc to benzaldehyde. This is the first example of a two-phase organic/perfluorous enantioselective catalytic system

Application of N,S-Chelating chiral Zinc bis(Arenthiolate) Complexes as New Precursor Catalysts in the Enantioselective Addition of diethylzinc to Aldehydes

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

De congenitale knieluxatie.

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The role of neutral and radical anionic organozinc complexes in the alkylation reactions of 1,4-diaza-1,3-butadienes with diorganozinc compounds

We have earlier postulated the intermediacy of organozinc radical species in the regioselective alkylation reactions of 1,4-di-tert-butyl-1,4-diaza-1,3-butadiene (t-BuNCHCHN-t-Bu) with diorganozinc compounds (ZnR2). To verify these postulates, we have prepared and studied the neutral organozinc radical complex MeO(CH2)3Zn(t-BuNCHCHN-t-Bu) (A) and two diorganozinc radical-anionic complexes, K[R2Zn(t-BuNCHCHN-t-Bu)] (R = Me (8a), Et (8b)). A was prepared in situ by the reaction of t-BuNCHCHN-t-Bu with bis(methoxypropyl)zinc. Complexes 8 were prepared by reducing the 1:1 coordination complex ZnMe2(t-BuNCHCHN-t-Bu) (1a) with potassium or by the nucleophilic addition of K(t-BuNCHCHN-t-Bu) to ZnR2 (R = Me, Et). The resulting radical-anionic complexes are thermally unstable and readily undergo an intermolecular single-electron transfer, giving a mixture of the metallacyclic heteroleptic zincate complexes K[ZnR(t-BuNCHCHN-t-Bu)] (9) and K[ZnR(t-BuNC(R)CHN-t-Bu)] (10). The ratio in which the latter complexes are formed depends on the R group and on the concentration and the temperature. Alternatively, 9 has been prepared separately from the reduction of [ZnR(t-BuNCHCHN-t-Bu)]2 (4) with 2 equiv of potassium. The crystal structures of two complexes of 9, i.e. {9a(THF)}n and {9c(Et2O)1/2}n, have been determined. Both complexes form linear coordination polymers containing alternating potassium cations and zinc-diazabutadiene anions

1:1 and 2:1 Lithium Zincates with Intramolecular Coordination. Structures of Li(thf)Zn(C6H4CH2NMe2-2)3 and Li2Zn(C6H4CH2NMe2-2)4

Homoleptic lithium zincates with intramolecular Li-N coordination, i.e., Li(thf)nZn(C6H4CH2NMe2-2)3 (n = 0 (1); n = 1 (1(thf))) and Li2Zn(C6H4CH2NMe2-2)4 (2) have been prepared by reacting [Li(C6H4CH2NMe2-2)]4 with Zn(C6H4CH2NMe2-2)2. In the solid state 1(thf) is a monomer containing a distorted tetrahedral zinc atom. The zinc is surrounded by three monoanionic C6H4CH2NMe2-2 (dmba) ligands, which all show a different bonding mode: 1-C bonding to zinc and nitrogen coordination to lithium; 1,2-C bridge bonding to zinc and lithium with Li-N coordination; and C,N-chelate bonded to zinc. One thf coordinates to lithium. In the solid state, 2 is a monomeric dilithium tetraarylzincate complex containing a tetrahedral zinc atom. The four dmba ligands are all similarly 1,2-C bridge-bonded to zinc and lithium, and each lithium is four-coordinate by two additional Li-N bonds. The reaction of LiCH2SiMe3 and Zn(C6H4CH2NMe2-2)2 did not give a mixed zincate complex but the respective homoleptic zincate complexes instead. Both homoleptic and in situ prepared mixed zincate complexes react readily with 2-cyclohexen-1-one, but the product composition shows that the in situ prepared zincate disproportionates into the corresponding homoleptic zincates prior to reaction

Synthesis and structural characterization of the homoleptic magnesium bis zincate complex Mg(thf) 6[Zn(CH2Ph)3]2

The addition of Mg(CH{2}Ph){2}(thf){2} to a thf solution of Zn(CH{2}Ph){2} yields the zincate complex Mg(thf){6}[Zn(CH{2}Ph){3}]{2} (1), which has been characterized by X-ray crystallography and NMR. Complex 1 is cleaved by tmeda into a 1:2 mixture of Mg(CH{2}Ph){2}(tmeda) and Zn(CH{2}Ph){2}(tmeda)