Lithium dicyclohexylamide

CHX2 group when treated with methylene halides and lithium dicyclohexylamide at low temperamres. " ... 

Unlike 1,3-dithiepin anion 144a, the evidence for the instability of 145a and for the lack of aromaticity associated with lOn-electron delocalization through the sulfur atom has been reported 91,92). The reaction of the disodium salt of c/s-dimercaptoethylene (155) with either l,2-dibromo-3-propanol or l,3-dibromo-2-propanol yielded 6,7-dihydro-5f/-l,4-dithiepin-6-ol (156). Treatment of the methoxy derivative 157 derived from 156 with two equivalents of lithium dicyclohexylamide resulted in an effective elimination of methanol to give 5//-l,4-dithiepin (145) as a colorless liquid. Lithiation of 145 with n-butyllithium in tetrahydrofuran at —70 °C... 

This preparation is patterned after the in situ preparation of dibromomethyllithium for addition to ketones using lithium dicyclohexylamide, as reported by Taguchi, H. Yamamoto, H. Nozaki, H. J. Am. Cham. Soc. 1974, 96, 3010. 

The Peterson reaction was reported240 to give a quantitative yield of methyl [(R),(Z)-2-/m-butyldiphenylsiloxymethylcyclobutylidene]acetate on treatment of (5)-2-(ter -butyldiphenyl-siloxymethyl)cyclobutanone with methyl trimethylsilylacetate and lithium dicyclohexylamide. 

Ethylenediamine, 157 Hexamethyldisilazane, 175, 331 Isopropylamine, 164 N-Lithioethylenediamine, 157, 200 Lithium amides, chiral, 159 Lithium 3-aminopropylamide, 157, 160 Lithium 3-aminopropylamide-Potas-sium /-butoxide, 160 Lithium dicyclohexylamide, 110 Lithium diisopropylamide, 106, 143, 148, 163, 188, 256, 257, 326 Lithium diisopropylamide-Hexa-methylphosphoric triamide, 143, 172 Lithium diisopropylamide-Potassium t-butoxide, 164... 

Kauffmann reported the first tellurium-lithium exchange reaction of a vinylic telluride with an organolithium compound.255 Phenyl vinyl telluride 168 was deprotonated by lithium dicyclohexylamide (LDCA) in THF, and the resulting vinyl anion 169 was reacted with chlorotrimethylsilane to give telluride 170. Vinylsilane telluroacetal 170 was then reacted with phenyllithium to give the corresponding vinyllithium, which was captured with chlorotrimethylsilane to give the bis-silylated ethane 171 (Scheme 96).255... 

The same type of ring opening was observed when salt 91 was treated with lithium amides or mesityllithium in THE at -78 °C. Addition of lithium diisopropylamide to 91 cleanly regenerated phosphaalkene 90 in 90% yield. When lithium dicyclohexylamide was used, a 50 50 mixture of / -(dicyclohexylamino)phosphaalkene 156 and its isomer 157 was isolated. Monitoring this reaction by P NMR at -78 °C proved the initial formation of 156 with phosphaalkene 157 only appeared on warming to room temperature. Lastly, yellow, oily 7 -(mesityl)phosphaalkene 158 resulted from the combination of 91 and mesityllithium (70%) <1994JA6149> (Scheme 51). 

Benzoditellurole 122 was metallated with lithium dicyclohexylamide at —80°C and the lithiated product 123 was then treated with methyl iodide to produce the methylated product 124 or with carbon dioxide to produce the carboxylic acid 125 (Scheme 5) <2000RCB1132>. 

Mesityllithium or lithium dicyclohexylamide react similarly with allyldimesitylborane (equation 19). Thus, boron-stabilized allyl units are available from either allyl- or vinyl-boranes. 

The production of boron-stabilized caibanions using steric hindrance on the borane to inhibit borate formation was fust demonstrated as part of a study of the properties of dimesitylboryl derivatives. Unlike the situation with dialkoxyboryl derivatives, it was possible to carry out the deprotonation with only one boron atom present and with no extra stabilizing groups. Either LDA or lithium dicyclohexylamide may be used as base, the latter being rather more efficient (equation 17). The initial study showed that the reaction with Mes2BCHR R was successful with RS R = H R = H, R = Me R = H, R = Ph andR ,R2 = Me. 

Lithium dicyclohexylamide [1, 610, before Lithium diethoxyaluminum hydride]. 

Dehydrohalogenation Alumina, see Sulfur tetrafluoride. Alumina-Potassium hydroxide. Cesium fluoride. l,5-Diazabicyclo[4.3.0]nonene-5. l,4-Diazabicyclo[2.2.2]octane. 1,5-Diazabicyclo[5.4.0]undecene-5. Dimethylaminotrimethylstannane. Dimethyl sulfoxide. Hexamethylphosphoric triamide. Lithium chloride. Lithium dicyclohexylamide. Magnesium oxide. Potassium r-butoxide. Potassium fluoride. Potassium triethylmethoxide. Pyridine, see Nitrosyl chloride. Silver fluoride. Silver nitrate. Sodium amide. Sodium bicarbonate, see Nitryl iodide. Sodium isopropoxide. Triethylamine, see Sulfur dioxide. 

A supplement entitled Lithium dicyclohexylamide" describes the preparation by Traynham e/ a/.34b of tran.v-cyclodecene by photochemical chlorination of cyclodecane to produce 1-chlorocyclodecane (4) and dehydrohalogenation of this substance with lithium dicyclohexylamide to form trans-cyclodecene in 70% yield. 

Although (7) reacts with methyl iodide and water predominantly at the a-carbon and with acetone mainly at the y-carbon, anion (8), which is readily prepared from the corresponding allyldimesityl-borane by treatment with mesityllithium or lithium dicyclohexylamide, reacts with both alkyl halides and... 

A variety of reagents will effect the conversion C(XTH2 - C(XrHC02R the decarbonylation of glyoxalate esters was described above. The most recently described reagent, methyl cyanoformate, reported by Mander and Sethi in 1983, allows the conversion of a preformed lithium enolate to the 3-keto ester in high yield (Scheme 68). Diethyl dicarbonate with potassium hydride in benzene effects the same reaction wiA symmetrical ketones, and with lithium dicyclohexylamide in ether introduces the ethoxycarbonyl group into the a -position of a,3-unsaturated ketones (Scheme 69)."" Diethyl carbon-... 

---