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 compound and a potassium
alkoxide
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, whe ...
. 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, 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
Benzylpotassium is an organopotassium compound with the formula C6H5CH2K. It is an orange powder. Like organo-alkali metal reagents in general, benzyl potassium is highly reactive, so much so that it reacts with most solvents. It is highly air se ...
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''-C
5H
11Li) 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''-C
5H
11K) 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