Organoalkali reagents

Butyllithium is commercially available as a solution in hexane in concentrations varying from 15 to 90 %. The dilute 15 % solution (1.5 mol/1) is most frequently used for syntheses on a laboratory scale. It is delivered in steel containers (containing up 

4 It is advisable to wear smooth-fitting protective disposable gloves while working with alkali metals and strongly basic reagents. 

5 With special equipment /i-butyllithium can be handled without problems on a technical scale information is supplied by Chemetall GmbH, Reuterweg 14, D-6000 Frankfurt am Main, FRG. 

If much synthetic work is to be carried out regularly with butyllithium, it may be economical to purchase a cylinder containing several liters of butyllithium. The solution is transferred into a number of dry 0.5 to 1 litre round-bottomed or conical flasks. It is advisable to empty the container in one operation, and to carry out this operation with two persons. For a large container (27 1) this takes 1.5 to 2 hours. 

Durst in Comprehensive Carbanion Chemistry E. Buncel, T. Durst (Ed) Elsevier, 1984, p. 239. 

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Most of the progress concerning organoalkali reagents in chemistry have been made using superbases. The following sections deal with the preparation and use of organoalkali compounds of vinyl, aryl, and benzyl type. 

S.7.5. from Lead(ll) Compounds with Organoalkali Reagents. 

The presence of the two amido protons in 3 also provides the opportunity to generate heterobimetallic clusters by reaction with organoalkali reagents. The magnesiated cubane 53 is produced in 69% yield from the reaction of dibutylmagnesium with 3 in hot THF. The reaction of 3 with two equivalents of butyllithium at -78 °C in THF generates 54 in 39% yield. The structure of the solvent-separated ion pair 54 is analogous to that of 41. 

For general instructions concerning handling organoalkali reagents, see Vol. 1. All temperatures are internal. 

M. Schlosser, in Organometallics in Synthesis, M. Schlosser, Ed., Wiley, Chichester 1994, 1 —166. Organoalkali Reagents. 

Organoalkali reagents are powerful alkylating agents in organic and organometallic chemistry. 

Halogen/metal permutation and hydrogen/metal permutation (usually apostrophed as "metalation") dominate the interconversion methods. They employ organoalkali reagents such as phenyllithium, methyllithium, -butyllithium, iec-butyllithium, or the superbasic LIC-KOR mixture. However, even if commercial, these reagents have to be made beforehand. The reaction of a chloro- or bromo-substituted hydrocarbon with lithium, sodium, or magnesium offers a standard entry to them. Thus, ultimately one always has to revert to the metal. 

A. A. Morton, Solid Organoalkali Metal Reagents, Gordon Breach, New York, 1964. 

All unsaturated hydrocarbons that possess removable allylic hydrogens or activated double bonds readily undergo oligomerization in the presence of basic reagents.30,31 Alkali metals, organoalkali compounds, and alkali alcoholates are most frequently applied. 

The formation of the metal hahde as a by-product limits the use of this method for the synthesis of reagents intended for further reactions. The relative solubihties of the organoalkali metal compounds and the metal hahdes formed in these reactions do not generally allow for easy separations. 

The assay of organoalkali metal reagent solutions can be performed using hydrolysis (equation 3), followed by simple acid base titration (equation 4). 

The reaction of an organo- or amido-alkah metal reagent with an acidic organic molecule produces an organoalkali metal compound and the amine or organic compound (equation 7). 

This is an excellent reaction for the conversion of most halides to acids containing one additional carbon atom. Carbonation of Grignard reagents and organoalkali compounds gives acids in yields of 50-85%. Ether solutions of the organometallic compounds formerly were treated with carbon dioxide gas at 10° to -10°. A more recent technique involves pouring the solution onto excess crushed Dry Ice. Carbon dioxide... 

A29. A. A. Morton, " Solid Organoalkali Metal Reagents. A New Chemical Theory for Ionic Aggregates. Gordon Breach, New York, 1964. 217 pp. The emphasis is on heterogeneous catalysis. 

For example, n-pentylsodium may be prepared in 80-90% yield by reaction between Na sand (25 jxra particle size) and 1-chloropentane in n-pentane at — 10°C in a creased flask equipped with a high-speed stirrer. Comparable 3delds of n-pentylsodium may be obtained in n-heptane, in which the yield of organoalkali decreases only from 85 to 75% after storage at RT for 24 days. In contrast, in n-BujO the yield of n-pentylsodium is 63%, but after 10 days most of the reagent has decomposed by reaction with the solvent. In 1,2-dimethoxyethane (DME) and 12 the yields of n-pentylsodium are < 15 %. Even under inert solvents samples of n-pentylsodium must be prepared and stored at RT or lower because pyrolysis is appreciable at 50°C and rapid at 100°C. 

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