Lithium dichloromethane

C. Cyclobutanone (Note 16). The residue consisting of oxaspiro-pentane (35%) and dichloromethane (about 200 ml.) is added dropwise at room temperature to a magnetically stirred solution containing about 5-10 mg. of lithium iodide in 50 ml. of dichloromethane (Notes 17, 18), at such a rate as to maintain gentle reflux of the solvent. At the end of the addition when the reaction mixture returns to room temperature, the transformation into cyclobutanone is complete. The dichloromethane solution is washed with 20 ml. of saturated aqueous sodium thiosulfate and with 20 ml. of water. After drying over magnesium sulfate and concentration by distillation of the solvent through a 15-cm., helix-packed, vacuum-insulated column, the residual liquid consists of cyclobutanone (95%) and of 3-buten-2-one and 2-methylpropenal... 

Caution Addition of lithium iodide catalytic amount to a dichloromethane solution containing more than 30% oxaspiropentane leads to a very vigorous reaction. 

Attempts to induce valence isomerization of 5W-dibcnz[c,e,]azepine (3) to dihydrophenanthro-[9,10-6]azirine under thermal conditions have failed.85 However, the aziridine 5 is formed, albeit in low yield (3 %), by irradiating the dibenzazepinc 3 in dichloromethane solution. Isomerization can also be achieved by deprotonation of SH-dibenzIr.eJazepine with lithium diiso-propylamide at — 78 "C, and then allowing the resulting anion 4 to reprotonate by heating the reaction mixture at 50°C.85... 

Chiral imines derived from 1-phenylethanone and (I. Sj-exo-l, 7,7-trimethyIbicyclo-[2.2.1]heptan-2-amine [(S)-isobornylamine], (.S>1-phenylethanamine or (R)-l-(1-naphthyl) ethanamine are transformed into the corresponding (vinylamino)dichloroboranes (e.g., 3) by treatment with trichloroborane and triethylamine in dichloromethane. Reaction of the chiral boron azaenolates with aromatic aldehydes at 25 "C, and subsequent acidic hydrolysis, furnishes aldol adducts with enantiomeric excesses in the range of 2.5 to 47.7%. Significantly lower asymmetric inductions are obtained from additions of the corresponding lithium and magnesium azaenolates. Best results arc achieved using (.S )-isobornylamine as the chiral auxiliary 3. 

A similar stereospecific conjugate addition to epoxysulfone 323 was also observed416. When this reaction of 323 was carried out with methyllithium at — 78 °C dichloromethane-diethyl ether (1 1) in the presence of lithium perchlorate, compounds 324 and 325 were obtained in a ratio of 95 5. On the other hand, in the treatment of 323... 

Catalysis by lithium perchlorate in dichloromethane Diels-Alder reactions and 1,3-Claisen rearrangements [100]... 

This anhydrous salt, and the mono- and di-hydrates of the analogous lithium and sodium salts, are all very impact-sensitive. The potassium salt, an intermediate in the preparation of hexanitroethane [1], was not allowed to become dry during isolation, but after precipitation was washed with methanol and dichloromethane and used wet with the latter for the succeeding nitration stage [2],... 

The enantiomerically pure indolizidine (—)-422 has been synthesized starting from L-malic acid diethyl ester 407. The hydroxyl function of L-malic acid diethyl ester 407 has been protected as dihydropyranyl ether 408 with 2/7-dihydropyran and Amberlyst 15 in pentane at room temperature. The diethyl ester 408 was then reduced with lithium aluminium hydride in diethyl ether under reflux and the newly generated hydroxyl functions then protected with mesyl chloride in the presence of triethylamine in dichloromethane at 0°C. This was converted into newly protected pyrroline nitrone 409 in 44% overall yield through a well-established method (Scheme 90). The regio-isomeric 5-pyrroline-iV-oxide 410 formed in 4% overall yield was easily separated by column chromatography <20000L2475>. 

The 10-57-5-hydridosiliconate ion 62 is known in association with lithium,323 tetrabutylammonium,101 and bis(phosphoranyl)iminium93 cations. It is synthesized by hydride addition to the 8-.S7-4-silane 63, which is derived from hexafluoroacetone.101 Benzaldehyde and related aryl aldehydes are reduced by solutions of 62 in dichloromethane at room temperature101 or in tetrahydrofuran at 0°96 within two hours. The alkyl aldehyde, 1-nonanal, is also reduced by 62 in tetrahydrofuran at O0.96 Good to excellent yields of the respective alcohols are obtained following hydrolytic workup. The reactions are not accelerated by addition of excess lithium chloride,96 but neutral 63 catalyzes the reaction, apparently through complexation of its silicon center with the carbonyl oxygen prior to delivery of hydride from 62.101... 

Another variation of this method involves the treatment of an acetonitrile solution of the aryl aldehyde, trimethylsilyl chloride, and either sodium iodide, if iodide products are desired, or lithium bromide, if bromide products are desired, with TMDO. After an appropriate reaction time (5-195 minutes) at a temperature in the range of —70° to 80°, the upper siloxane layer is removed and the benzyl iodide or bromide product is isolated from the remaining lower portion after precipitation of the inorganic salts by addition of dichloromethane. For example, p-anisaldehyde reacts to form /i-rnethoxybenzyl bromide in 84% isolated yield under these conditions (Eq. 200).314,356... 

Thus, the unsubstituted starting compound 69 was treated with resorcinol in the presence of trifluoroacetic acid (TFA) to yield 70. Then, reaction of 69 with the cyclic a,/3-unsaturated ketone in the presence of lithium hydride gave the 7-substituted heteroaromatic compound 71, and ethyl cyanoacetate afforded the cross-conjugated product 72, whereas reaction with pyrimidine-2,4,6-trione in the presence of triethylamine yielded the addition product 73. Indole also been reacted with 69, and heating of the dichloromethane solution for 90 min in the presence of TFA yielded the addition product 74 in excellent yield (95%) <1998ZOR450> (Scheme 12). 

Complete control of the diastereoselectivity of the synthesis of 1,3-diols has been achieved by reagent selection in a one-pot tandem aldol-reduction sequence (see Scheme l). i Anti-selective method (a) employs titanium(IV) chloride at 5°C, followed by Ti(OPr )4, whereas method (b), using the tetrachloride with a base at -78 °C followed by lithium aluminium hydride, reverses the selectivity. A non-polar solvent is required (e.g. toluene or dichloromethane, not diethyl ether or THF), and at the lower temperature the titanium alkoxide cannot bring about the reduction of the aldol. Tertiary alkoxides also fail, indicating a similarity with the mechanism of Meerwein-Ponndorf reduction. 

Tetraphenyltellurophene To a suspension of 1,4-dilithiotetraphenyl-l,3-butadiene in 100 mL of ether, prepared from 10 g (56 mmol) of diphenyl acetylene and excess of lithium, is added over 15 min a solution of TeCl4 (5.3 g, 19.7 mmol). The green mixture is poured into a mixture of CH2CI2 and water, the organic phase is separated, filtered through anhydrous MgS04, filtered and evaporated. The residue is recrystallized from dichloromethane/ethanol, giving tetraphenyltellurophene 5.35 g (56%), m.p. 239°C. 

H-l,3-ditellurole. Under an atmosphere of argon, 0.23 g (2.4 mmol) of trimethylsily-lacetylene are dissolved in 5 mL dry tetrahydrofuran. The solution is cooled to -70°C. n-Butyl lithium (1.0 mL, 2.4 M, 24 mmol) is dropped into the stirred solution. Then 0.20 g (2.0 mmol) of tellurium powder is added. The mixture is warmed to 20°C and kept at this temperature for 2 h. To this mixture, cooled again to -70°C, is added a solution of 0.35 g (2.0 mmol) of chloroiodomethane in 1 mL of tetrahydrofuran. The mixture is stirred for 15 min and then quenched with 50 mL water. The product is extracted with three 15 mL portions of dichloromethane. The combined extracts are washed with brine, dried with anhydrous sodium sulphate and filtered. The filtrate is concentrated to give trimethylsilylethynyl chloromethyl tellurium as a pale-yellow oil. Tellurium powder (0.125 g, 1.0 mmol) is added to 2 mL of a 1 M solution (2.0 mmol) of lithium triethylborohydride in ethanol. The mixture is stirred at 20°C for 2 h under an atmosphere of argon. Then 2 mL of 1 M sodinm ethoxide in ethanol are added followed by 0.27 g (1.0 mmol) of trimethylsilylethynyl chloromethyl tellurium dissolved in 2 mL dimethylformamide. The mixture is stirred for 15 h at 20°C, then diluted with 25 mL water and extracted with three 15 mL portions of dichloromethane. The combined extracts are dried with anhydrons sodinm snlphate, fdtered and the filtrate concentrated. The residue is chromatographed on silica gel with hexane/dichloromethane (1 1) as mobile phase. The fractions containing the prodnct are concentrated and recrystallized from methanol 65% yield, m.p. 85°C. 

Diphenyl telluropyran-4-one (typicalprocedure)7° 120 mL (0.12 mol) of a 1.0 M solution of lithium triethylborohydride in tetrahydrofuran are added to 7.65 g (60 mmol) of powdered tellurium under nitrogen, and the mixture stirred at 20°C for 4 h. A solution of sodium ethoxide (prepared from 5.52 g (0.24 mol) of sodium and 240 mL of absolute alcohol) is added to the dilithium telluride, 13.8 g (60 mmol) of bis(phenylethynyl) ketone are dissolved in a mixture of 150 mL of tetrahydrofuran and 150 mL of 1 M sodium ethoxide in ethanol this solution is poured as quickly as possible into the deep-purple-coloured dilithium telluride soluhon. The flask containing the reaction mixture is immediately placed in a water bath at 50°C and the temperature slowly increased over 30 min until ethanol begins to condense on the side of the flask. The water bath is removed and the mixture is stirred overnight at 20°C. Dichloromethane (400 mL) is then added, the resultant mixture is washed with 800 mL of water, and the organic phase is separated and concentrated to an oil. The oil is dissolved in 600 mL of dichloromethane, and the solution is filtered through a pad of sand. The filtrate is washed with 200 mL of 2% aqueous sodium chloride soluhon, dried with anhydrous sodium sulphate, filtered and evaporated. The brownish solid residue is triturated with 20 mL of butanenitrile and the fine yellow solid is collected by filtration yield 10.9 g (51%) m.p. 126-129°C (from acetonitrile). 

The reaction of dichloromethane (or its dideuterio derivative) (430) with lithium and a catalytic amount of DTBB (5%) in the presence of a carbonyl compound as electrophile in THF at —40 °C led, after final hydrolysis with water, to the corresponding 1,3-diols... 

In the Mukaiyama aldol additions of trimethyl-(l-phenyl-propenyloxy)-silane to give benzaldehyde and cinnamaldehyde catalyzed by 7 mol% supported scandium catalyst, a 1 1 mixture of diastereomers was obtained. Again, the dendritic catalyst could be recycled easily without any loss in performance. The scandium cross-linked dendritic material appeared to be an efficient catalyst for the Diels-Alder reaction between methyl vinyl ketone and cyclopentadiene. The Diels-Alder adduct was formed in dichloromethane at 0°C in 79% yield with an endo/exo ratio of 85 15. The material was also used as a Friedel-Crafts acylation catalyst (contain-ing7mol% scandium) for the formation of / -methoxyacetophenone (in a 73% yield) from anisole, acetic acid anhydride, and lithium perchlorate at 50°C in nitromethane. 

Acid treatment of a 3 1 mixture of murrayafoline A (7) and koenoline (8) led to chrestifoline A (192) in 70% yield. Addition of murrayafoline A (7) to a mixture of 1057 and lithium aluminum hydride in ether and dichloromethane afforded bismurrayafoline-A (197) in 19% yield (662) (Scheme 5.166). In addition to the aforementioned methods, the same group also reported a stereoselective synthesis of axially chiral bis-carbazole alkaloids by application of their "lactone concept" (663) and a reductive biaryl coupling leading to 2,2 -bis-carbazoles (664). 

Dichloromethane and triethylamine were distilled from calcium hydride before use. Silica gel 60. 0.040-0.063 mm (Merck) was used for column choromatography. Lithium aluminum hydride (95%, powder) was obtained from Aldrich Chemical Co., Inc. 

B. (2S, 3R)-2,4-Dimethyl-1,3-pentanediol3. To a stirred solution of (+)-2 (2.75 g, 5 mmol, 96 4 isomeric purity) in tetrahydrofuran (THF) (50 mL) is added lithium aluminum hydride (0.19 g, 5 mmol) at 0°C. The reaction mixture is stirred at room temperature for 1 hr and quenched by the careful addition of sodium sulfate decahydrate (5 g). The mixture is stirred vigorously for 30 min and filtered. The filtrate is concentrated, dissolved in 75 mL of a 1 1 mixture of hexane and dichloromethane. This solution is dried over sodium sulfate, filtered and concentrated under reduced pressure. Trituration of the resulting oil with hexane (50 ml) results in the precipitation of auxiliary alcohol 4 (1.6-1.8 g) which is recovered by filtration (Note 11). The residue is separated by chromatography over silica gel (40 g) (Note 2) with hexane and ethyl acetate (3 1-1 1) to afford additional 4 (0.2-0.4 g. Note 12) and 3 (0.60 g, 92%) (Notes 13, 14). 

The dependence of the counterion and of the solvent99 was studied in the addition of sec-butyl and tert-butyl mercaptide to methyl 4-bromocrotonate (3). The highest yield of the Michael addition induced cyclopropane product 10 was observed with lithium as counterion in dichloromethane or pentane as solvent. 

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