Mono complexes lithium

The addition reactions of alkyllithium-lithium bromide complexes to a-trimethylsilyl vinyl sulfones that have as a chiral auxiliary a y-mono-thioacetal moiety derived from ( + )-camphor are highly diastereoselective. A transition state that involves chelation of the organolithium reagent to the oxygen of the thioacetal moiety has been invoked. The adducts are readily converted via hydrolysis, to chiral a-substituted aldehydes22. 

The synthesis, structures, and reactivity of neutral and cationic mono- and bis(guanidinato)zirconium(rV) complexes have been studied in detail. Either salt-metathesis using preformed lithium guanidinates or carbodiimide insertion of zirconium amides can be employed. Typical examples for these two main synthetic routes are illustrated in Schemes 73 and 74. Various cr-alkyl complexes and cationic species derived from these precursors have been prepared and structurally characterized. 

Titanium imido complexes supported by amidinate ligands form an interesting and well-investigated class of early transition metal amidinato complexes. Metathetical reactions between the readily accessible titanium imide precursors Ti( = NR)Cl2(py)3 with lithium amidinates according to Scheme 84 afforded either terminal or bridging imido complexes depending on the steiic bulk of the amidinate anion. In solution, the mononuclear bis(pyridine) adducts exist in temperature-dependent, dynamic equilibrium with their mono(pyiidine) homologs and free pyridine. 

We came up with the idea of using a dummy ligand, as shown in Scheme 1.23 [34]. Reaction of dimethylzinc with our chiral modifier (amino-alcohol) 46 provided the methylzinc complex 62, which was subsequently reacted with 1 equiv of MeOH, to form chiral zinc alkoxide 63, generating a total of 2 moles of methane. Addition of lithium acetylide to 63 would generate an ate complex 64. The ate complex 64 should exist in equilibrium with the monomeric zincate 65 and the dimer 66. However, we expected that the monomer ate complex 64 and the mono-... 

Although direct reaction of lanthanide mono-porphyrins with free phthalo-cyanine or its lithium derivatives is generally more efficient than the template synthesis, and gives rise to mixed-ligand complexes, the template strategy can also be applied for synthesis of phthalocyanine-porphyrin complexes, as in the case of unsymmetric bisphthalocyanine complexes (Scheme 8.2, B(b)) [106, 136, 145, 146]. Thus, metallation of free porphyrins with lanthanide salts in TCB or n-octanol leads to single-decker complexes, which then react with phthalonitriles under the action of DBU in alcoholic media to give the desired compounds. 

For application in organic synthesis, the regiochemistry of insertion of carbenoids into un-symmetrical zirconacydes needs to be predictable. In the case of insertion into mono- and bicydic zirconacydopentenes where there is an wide variety of metal carbenoids insert selectively into the zirconium—alkyl bond [48,59,86], For more complex systems, the regiocon-trol has only been studied for the insertion of lithium chloroallylides (as in Section 3.3.2) [60]. Representative examples of regiocontrol relating to the insertion of lithium chloroal-lylide are shown in Fig. 3.2. 

The apparatus and procedures are similar to those in the preparation above and a 1L flask is used. A solution of lithium tri-ferf-butoxyhydridoaluminate 9 (28.6 g, 113 mmole) in purified THF (100 mL) is added slowly to a solution of ZrCl2(i7s-C5Hs)2 (32.9 g, 113 mmole) in THF (500 mL) with stirring. After complete addition, stirring is continued for 1 hour, after which the mono-hydrido complex is collected by anearobic filtration (Fig. 1) and washed with THF (yield 26.3 g, 90%). Anal. Calcd. for C10H ClZr ash (Zr02), 47.77% hydrolyzable H, 1.00 g-atom/mole Cl, 13.75. Found ash, 47.0% hydrolyzable H, 1.02 g-atom/mole Cl, 13.4. One-quarter mole of Li[AlH4] may be used instead of the tri-terr-butoxy hydrido complex, but the essential control of stoichiometry is more difficult (see Properties). 

Flow fluorination of the 4,4 -bipyridine —boron trifluoride complex gives only mono-fluorinated l-fluoro-4-(4-pyridyl)pyridinium boron trifluoride tetrafluoroborate (31), while fluorination of l-methyl-4-(4-pyridyl)pyridinium triflate in the presence of lithium triflate provides l-fluoro-l -methyl-4,4 -bipyridinium ditriflatc (32) 67... 

Other salts probably have similar effects but have not been studied extensively. Lithium salts have little influence on the termination reaction but can increase the propagation rate, presumably by complexing the growing nitrile radical (14). Anions complex with the growing chain in the order Cl> N03> C104. Complex formation between salt and mono-... 

Formed from the imine using LDA in hexane, NMR studies reveal complex solvent-dependent distributions of monomers, dimers, and trimers in several ethereal solvents, although a mono-solvated dimer can be selected by appropriate choice of solvent. Study of C-alkylation rates suggests that both monomer- and dimer-based mechanisms operate. The lithioimines were compared with the isostructural lithium dialkylamides, but were shown to be not simply vinylogous analogues thereof. 

Mono- or di-lithium salts of (7 )-BINOL give high yields and good ees in cyanations of aromatic aldehydes.262 Formation of an aqua (or alcohol) complex of the catalyst gives higher and reversed ee, and non-linear effects in some cases. 

Using this reaction, we were able to prepare both the mono and disubstituted derivatives, N3P3F,C(OC2H,)=CH2 and N3P3F [C(0C2H3)=CH2]2, without any of the by-product observed in tne case of the propenyl lithium reaction. Similar results were obtained starting with methylvinyl ether. Attempts to achieve trisubstitution led to a complex series of reactions involving... 

Arnold and co-workers also reported the deprotonation of alkoxy imi-dazolium iodides with -butyl lithium to yield lithium alkoxide carbenes (Scheme 3).14 Single crystals of one of the complexes were grown from a diethyl ether solution, and revealed a dimer of LiL with lithium iodide incorporated to form a tetramer of lithium cations (7). The lithium-NHC bond distance of 2.131(6) A is similar to that of the lithium amide carbene 4. Also as in 4 there is distortion of the lithium-NCN bond which has an angle of 152.3°. The C2 carbon resonates at 200 ppm in the 13C NMR spectrum which is a relatively high-frequency, possibly as a result of the incorporated lithium iodide. The lithium salts were able to act as ligand transfer reagents and react with copper (II) chloride or triflate to afford mono- or bis-substituted copper(II) alkoxy carbene complexes. 

Hill expanded the range of bis(iminophosphorano)methanides with the lithium20 and potassium21 complexes 9 and 10. Complex 9 was prepared from the reaction of n-butyl lithium with the parent methane in ether and was crystallised as a mono-etherate which was found to not exhibit a lithium-methanide contact. The potassium complex 10 was prepared from the parent methane and potassium bis(trimethylsilyl)amide in toluene. A structural investigation revealed 10 to be a dimer formed by r 6-mesityl---potassium interactions, but a potassium-methanide contact was not observed. 

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