Schlosser's base (or Lochmann-Schlosser base) describes various

superbasic SuperBASIC is an advanced variant of the BASIC programming language with many structured programming additions. It was developed at Sinclair Research by Jan Jones during the early 1980s. Originally SuperBASIC was intended as the BASIC interprete ...

mixtures of an

alkyllithium In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom ...

compound and a potassium alkoxide. The reagent is named after Manfred Schlosser, although he uses the term ''LICKOR superbase'' (LIC denoting the alkyllithium, and KOR denoting the potassium alkoxide). The superbasic nature of the reagent is a consequence of the ''in situ'' formation of the corresponding

organopotassium compound Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are ...

, as well as changes to the aggregation state of the alkyllithium species.

Preparation and reactivity

Commonly, the mixture called Schlosser's base is produced by combining ''n''-butyllithium and potassium ''tert''-butoxide in a one-to-one ratio. The high reactivity of Schlosser's base is exploited in synthetic organic chemistry for the preparation of organometallic reagents. For example, potassium benzyl can be prepared from toluene using this reagent. Benzene and ''cis/trans''-2-butene are also readily metalated by Schlosser's base. Toluene, benzene, and butenes react only slowly with alkyllithium reagents and not at all with potassium alkoxides, yet they react rapidly with a mixture of the two. Although there are similarities, the reactivities of Schlosser's base and the isolated alkylpotassium reagent are not identical.

Structure

The structure of Schlosser's base is complex. A study of the base prepared from neopentyllithium (''neo''-C₅H₁₁Li) and potassium ''t''-butoxide (''t''-BuOK) has led to the spectroscopic and crystallographic identification of a series of constituent bimetallic clusters:

Li''_x''K_''y''(''neo''-C₅H₁₁)''_z''(''t''-BuO)''_w'', ''x'' + ''y'' = ''z'' + ''w'' = 7 or 8,

in equilibrium with neopentylpotassium (''neo''-C₅H₁₁K) and lithium ''t''-butoxide (''t''-BuOLi).{{Cite journal, last=Benrath, first=Philipp, last2=Kaiser, first2=Maximilian, last3=Limbach, first3=Thomas, last4=Mondeshki, first4=Mihail, last5=Klett, first5=Jan, date=2016-08-26, title=Combining Neopentyllithium with Potassium tert-Butoxide: Formation of an Alkane-Soluble Lochmann–Schlosser Superbase, journal=Angewandte Chemie International Edition, language=en, volume=55, issue=36, pages=10886–10889, doi=10.1002/anie.201602792, pmid=27392232, issn=1521-3773

References

Bases (chemistry) Superbases Potassium compounds