Lochmann bases

A broad scope is documented for the preparation of suspensions of 2-alkenylpotassium lithium toV-butoxide complexes from unsaturated hydrocarbons by means of butyllithium/ potassium /erf-butoxidc (Schlosser Lochmann base LICKOR reagents )38-45,432 456. Examples are given in Section D.1.3.3.3.3.2.1. 

Reactions of the Lochmann base (a mixture of butyllithium with potassium re/T.-butoxide in pentane [195]), with conjugated polyenes yield fully delocalized carbanions in high yield at a high rate [196]... 

X-ray crystallography is by now one of the most important methods for the determination of carbanion structures. From the very large number of recently characterized carbanions only a few can be mentioned here. They include preparatively important species such as the first lithiated carbamide [29], the lithium and tetra- -butyl ammonium salts of a a-sulfonyl substituted carbanion [30], and a protoype of the synthetically very useful Lochmann bases. [31] On the other hand structural work - both by X-ray crystallography and by various modem NMR spectros-... 

In general, however, particularly strong bases are required in order to bring about the deprotonation of alkyl ethers. Thus, the metalation of f-butyl methyl ether has been reported to be feasible by means of the Lochmann-Schlosser base (equation 29) a-lithiated tetrahydrofuran, however, undergoes a fragmentation to give ethene and lithium ethenoate . 

Sometimes referred to as the Lochmann-Schlosser Base) n-BuLi / t-BuO" K+... 

Starting from (Z)-l,2-dimethoxyethene, the Z-isomer of 1,2-dimethoxyvinyl anion was prepared by deprotonation with the Lochmann-Schlosser base at — 78 °C, being trapped with methyl chloroformate to provide the acrylate 579857 (Scheme 157). This compound was further lithiated at the /i-position to give a /LacyI vinyllithium858 which, after reaction with benzaldehyde, was transformed into the a./Lbulenolide 580. 

P-Substituted glucals 645 and 646, bearing a benzyloxy and a phenylsulfanyl group, have been deprotonated with the Lochmann-Schlosser base and LDA or f-BuLi, respectively. After reacting with electrophiles, these intermediates provide functionalized C-... 

The deprotonation of l-(methylsulfanyl)buta-l,3-diene cannot be performed with n-BuLi, but the Lochmann-Schlosser base, followed by addition of lithium bromide, afforded stereospecihcally dienyllithiums ( )-716 and (Z)-7161006 1012. These intermediates are configurationally stable below —20 °C1013 but they have not been further used as crotonyl anion equivalents. 

The requirement of extensive allyl anion stabilization as a prerequisite for cyclopropyl anion opening has only been overcome in the treatment of arylcyclopropanes such as 16 and 20 with Lochmann s base (BuLi//-BuOK) in refluxing hexane. Under these conditions poly-metalated 17 and dimetalated species 21, respectively, were formed. The ring opening results from the need for the charge in the benzylic cyclopropyl position to be further removed from... 

A more versatile approach to 4,7-disubstituted dihydroacepentalenes 65 is via the stable acepentalene dianion 64 as an easily accessible intermediate. Dipotassium acepentalenediide 64 can be obtained in virtually quantitative yield by treatment of triquinacene 10 with the superbasic mixture of potassium f-pent-oxide and butyllithium [or even better potassium f-butoxide, butyllithium and tetramethylethylenediamine (TMEDA)] in hexane, the so-called Lochmann-Schlosser base (Scheme 15) [62, 63]. Mechanistically this transformation has... 

The facile formation of dipotassium tribenzoacepentalenediide 184 has opened efficient and versatile syntheses of further 1,4-disubstituted tribenzo-1,4-dihydroacepentalenes such as 190-193 [108,109] (Scheme 38). These analogues of 169 and 170 are not accessible via tribromide 145 (cf. Scheme 33). Use of the hexane-soluble Lochmann-Schlosser base Li(2-ethylhexyl)/KOtBu allows one to synthesize the bis(trimethylsilyl) compound 190 in almost quantitative yield. The functionalized tribenzodihydroacepentalenes 190-193 are relatively unstable at room temperature, but addition of protic acids can be performed leading to further mixed 1,4,7-trisubstituted tribenzotriquinacenes such as 194 and 195 (Scheme 38, cf. Scheme 34). Most remarkable is the conversion of the labile bis(stannyl) derivative 193 (obtained in 42% yield) into the corresponding dilithium salt 196, which co-crystallizes with six molecules of dime-thoxyethane (DME). X-ray crystal structure analysis revealed that 196 forms solvent-separated ion triplets consisting of ribbon-like layers of tribenzoacepentalenediide ions alternating with layers of [Li+ 3 DME] chelates [108]. In contrast, the analogous non-benzoannelated salt forms contact-ion triplets [33]. 

The paper of Bates and Ogle [3] mentions the successful formation of the p-xylene dianion from p-xylene and the Lochmann-Schlosser base, BuLi r-BuOK,... 

The finding that lithiation of la took place selectively at the aromatic ring rather than the benzyl position opened a way for the functionalization of la in a regioselective manner by means of metalation [58]. Thus la was treated with 3 equiv. of the Lochmann s base (t-BuOK, n-BuLi) in hexane and then the reaction was quenched with appropriate electrophiles, giving monosubstituted products lb, II, Ip, and Iq (Structures 2 and 22, Scheme 14) in good yields. When more excess base was employed, para-disubstitution products Ic, Im, and Ir... 

We have synthesized some novel silarylene and silarylenesiloxane polymers via dicarbanions prepared from Lochmann s base. Lochmann s base, a powerful metalating reagent composed of equimolar amounts of n-butyl lithium and potassium r-butoxide in a hydrocarbon, has been used to dimetalate compounds such as m-xylene, 4,4 -dimethylbi-phenyl, and 2,3-dimethyl-1,3-butadiene in good yields. In this work the dicarbanion of m-xylene and 4,4 -dimethylbiphenyl have been used to prepare silicon containing monomers and polymers by two different routes. The first route involves a 1 1 condensation reaction between the dicarbanion and a dichlorodiorganosilane to produce a condensation polymer. The second route involves reaction of the dicarbanion with a chlorodiorganosilane which is then converted to a bis(silanol) and then polymerized. Spectroscopic as well as thermal characterization will be presented on the polymers which have been described. 

Allyl-SMP 1 is easily to deprotonate with the Lochmann-Schlosser base at -78 °C in TBME. Subsequent silylation with DMPSCl provides quantitatively the -silylated enamine 2, which can be metallated directly again in the same pot... 

The new hydrazones were first tested in simple a-alkylation reactions. As is shown in scheme 14, metalation with Lochmann-Schlosser base in THF at low temperature yielded highly reactive azaenolates, which were alkylated by a number of alkyl halides at -100°C in good yields and with high diastereomeric excess (de = 85 - > 95%). It is noteworthy that, besides the usual oxidative cleavage with ozone, the SAMP-hydrazones could be converted without racemization to the final 3-substituted 2-oxoesters under very mild conditions with boron trifluoride-ether in acetone/water with the addition of paraformaldehyde. Thus, this method permitted for the first time the highly enantioselective transfer of a homologous pyruvate unit to electrophiles (scheme 14) [41]. 

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