Lithium boronate

The enolates of other carbonyl compounds can be used in mixed aldol reactions. Extensive use has been made of the enolates of esters, thiol esters, amides, and imides, including several that serve as chiral auxiliaries. The methods for formation of these enolates are similar to those for ketones. Lithium, boron, titanium, and tin derivatives have all been widely used. The silyl ethers of ester enolates, which are called silyl ketene acetals, show reactivity that is analogous to silyl enol ethers and are covalent equivalents of ester enolates. The silyl thioketene acetal derivatives of thiol esters are also useful. The reactions of these enolate equivalents are discussed in Section 2.1.4. 

These oxazolidinones can be acylated and converted to the lithium, boron, tin, or titanium enolates by the same methods applicable to ketones and esters. For example, when they are converted to boron enolates using di-n-butylboron triflate and triethyl-amine, the enolates are the Z-stereoisomers.125... 

Tomascak PB, Hemming NG, Pedone VA(2001) Lithium, boron, and strontium isotope constraints on solute sources for the Great Salt Lake, Utah. Eleventh VM Goldschmidt Conf Abst, LPI Contribution 1088, Lunar Planetary Institute, 3758... 

You CF, Chan LH, Spivack AJ, Gieskes JM (1995) Lithium, boron, and their isotopes in ODP Site 808, Nankai Trough sediments and pore waters Implications for fluid expulsion in accretionary prisms. Geology 23 ... 

Synthesis methodology is expanded to cover a range of new reagents, including oxidants and reductants reagents for asymmetric synthesis and those derived from lithium, boron, silicon, phosphorus and sulphur. 

PBs featuring para-phenylene spacers have also been prepared. Marder reported the synthesis of derivative 16a (related to the ethynyl-bridged compound 5a) by bromine-lithium-boron exchange... 

Using the bromine-lithium-boron exchange strategy, Muller and Lachmann reported in 1993 a series of MPB, DPB, and TPB 27-29 (Scheme 20) All of these compounds were isolated by crystallization and characterized by IR, multinuclear NMR (aH, 13C, 31P, and 11B), and elemental analysis. The presence of P-B interactions was spectroscopically apparent and monomeric closed structures were authenticated crys-tallographically for 27 and 28 (see Section III). 

Kent NL, McCance RA. 1941. The absorption and excretion of minor elements by man. I. Silver, gold, lithium, boron and vanadium. Biochemical Journal 35 837-844. 

Elements other than hydrogen, lithium, boron, carbon and silicon were virtually unknown as substituents on the borazine N-atoms. Fairly recently, Paetzold 5 obtained hexachloroborazine by thermal decomposition of (Cl2BN3)3. It may be noted that N—N substituted borazines have not yet been isolated, though attempts have been made to prepare such materials 53>. However, formation of tetrakis(diethylamino)-l,3,2,4-diazadiborine was accomplished by photolytic decomposition of bis (diethylamino)azidoborane 54> in solution as shown in Eq. (12). 

W. B. Clarke, R. S. Gibson, Lithium, boron and nitrogen in 1-day composites and a mixed-diet standard, J. Food Comp. Anal., 1 (1988), 209-220. 

Syn-, anti- and acetate aldol derivatives can be synthesized by choosing appropriate enolization protocols (Scheme 5) [20]. With lithium, boron and tin Lewis acids,. tyn-aldols can be obtained via (Z)-enolates [21]. If enolization is carried out with lithium or tin, there are enough open coordination sites available to position the aldehyde and the enolate in accordance with the chelate model for the sultam auxiliary and with the Zim-mermann-Traxler model. The combination of these models predicts the formation of 22, which is indeed experimentally obtained. If Lewis acids with only two open coordination sites are used... 

SAFETY PROFILE Poison by ingestion, inhalation, and skin contact. Flammable can liberate H2. Incompatible with H2O as moisture on fibers of cellulose or as liquid. See also LITHIUM, BORON COMPOUNDS, and HYDRIDES. 

Though aluminum and magnesium alkyls are most important, lithium, boron and zinc alkyls are also useful in niche polyethylene applications. While in-depth discussions of production, properties and applications of metal alkyls are outside the scope of this book, key industrial methods for production of... 

Third, some elements have anomalous abundances. Hydrogen and helium and iron have anomalously high concentrations. H and He have been discussed already. In the case of Fe this relates to the high binding energy and associated stability for Fe. The elements lithium, boron, and beryllium have anomalously low concentrations for they are not produced in stellar nucleosynthesis, as already discussed. 

In addition to tritium produced by ternary fission, as shown in Table 8.1, tritium is also produced in reactors by neutron reactions with lithium, boron, and deuterium. Reactors can be designed to produce tritium by irradiating lithium targets with thermal neutrons, resulting in the (/I, a) reaction ... 

Alternative enolization method. Other methods of enolate generation could well be of use in reducing the reagent quantities. We examined firstly generating the lithium enolate with LDA and then carrying out a lithium-boron exchange. In a model system, this worked well, as... 

While the number of possible different alkyl radicals is very large, the following are the principal ones of technical importance methyl, ethyl, propyl, butyl, amyl, and hexyl. The introduction of the aralkyl or benzyl radical, as well as the unsaturated allyl group, also is included here, for they are technically important. There are many other miscellaneous alkylations, e.g., involving bonding to lithium, boron, phosphorus, germanium, thallium, selenium, etc. 

Table I. Isotope Compositions in Natural Hydrogen, Lithium, Boron, and...

Theoretical Development. Separating isotopes on an industrial scale, where the components are chemically identical and differ physically only in mass, represented a new chemical engineering challenge. As shown in Table I, the challenge was made more difScult in that the desired isotopes deuterium, lithium , boron , and uranium were of low concentration in their respective naturally occurring parent elements. 

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