- Tripod Ligands with Three Different Donor Groups: Synthesis and Coordination of CH3C(CH2PR2)(CH2PR'2)(CH2PR"2)
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Tripod ligands CH3C(CH2PR2)(CH2PR'2)(CH2PR"2), 6(a-e), with three different donor groups are obtained from CH3C(CH2Cl)(CH2Br)(CH2OSO2CF3), 3, by successive replacement of the three different leaving groups. 3 itself is easily accessible from CH3C(CH2OH)3 in a few simple steps.The general applicability of this strategy is demonstrated by the preparation of five different ligands 6(a-e).For one specific example (6a) the coordination behavior is exemplified by the synthesis of its Mo(CO)3 derivative: CH3C(CH2P(Ph)2)(CH2P(3-Tol)2)(CH2P(4-Tol)2)*Mo(CO)3 (7).All compounds, including their intermediates CH3C(CH2Cl)(CH2Br)(CH2PR2), 4(a-c), and CH3C(CH2PR2)(CH2PR'2)(CH2Cl), 5(a-c), have been obtained in an analytically pure state and fully characterized by their spectroscopic data.The methods developed lend themselves to the almost deliberate shaping of tripod metal templates.Key words: Chiral Tripod Ligands, Chiral Tripod-Molybdenum Complexes, Synthesis, Chiral Triphosphines, Functionalized Neopentyl Compounds
- Heidel, Horst,Huttner, Gottfried,Helmchen, Guenter
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p. 1681 - 1692
(2007/10/02)
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- Cyclic Trimerization of Oxetanes
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Conditions for obtaining the optimum yield of the cyclic trimer in the cationic oligomerization of oxetanes have been determined.At moderate dilution (0.05 M) with catalytic quantities of BF3 in CH2Cl2, the yield of the cyclic trimer (1,5,9-trioxacyclododecane) from oxetane could be increased to 50percent at the expense of the cyclic tetramer (1,5,9,13-tetraoxacyclohexadecane), 12percent, and polymer.In contrast, 3,3-dimethyloxetane consumed the BF3 catalyst, which had to be renewed, producing, in a slow reaction, a homologous series of fluorohydrins, together with cyclic oligoethers.The fluorohydrins cyclized if treated with gaseous BF3 before work-up, boosting the isolated yields to 20percent cyclic trimer and 8percent cyclic tetramer.With PF5 in CH2Cl2 the catalyst was stable and the reaction fast, and no fluorohydrins were formed; no cyclic trimer but 73percent cyclic tetramer could be isolated.Other solvents (benzene, CHCl=CCl2, CH2ClCH2Cl), other catalysts (SbF5, AlEt3) and other oxetanes (3-methoxymethyl-3-methyloxetane, 3-halomethyl-3-methyloxetane) were also examined.
- Dale, Johannes,Fredriksen, Siw B.
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