Kugelrohr

The submitters purified the product by distillation in a Kugelrohr apparatus with an oven temperature of 85-88 C (20 mm) and obtained 3.80-3.85 g (88-89%). The purity of the product was 93-96% according to GLC analysis. The major impurity (2-6%) was 1-acetyl-2-methy1cyclohexene. 

On 0.01-raol scale the yield of ethyl 2,3-pentadienoate is 0.79-0.93 g (64-74%). The product was purified by bulb-to-bulb distillation with a Kugelrohr apparatus at 12-14 rm with an oven temperature at 75-85 C. 

In a typical case, ethylamine is allowed to react with ethylene oxide to produce N-ethyldiethanolamine (5). The latter is then treated with additional ethylene oxide to afford N,N-di(polyoxyethylene)ethylamine (6) where the sum a -t b is 3. This material is then stirred at room temperature for 3 h with toluenesulfonyl chloride and powdered sodium hydroxide in dioxane solution. After filtration and Kugelrohr distillation, N-eth-ylmonoaza-15-crown-5 is isolated in 75% yield as illustrated below in Eq. (4.7). 

In this method, an oligoethylene glycol is treated with 0.3 eq. of sodium bromoace-tate in methanol. The resulting monocarboxylic acid salt is then treated with toluene-sulfonyl chloride, sodium carbonate and dioxane. After heating the reaction mixture at 50° for an hour, the product was obtained either by Kugelrohr distillation or extraction. The two compounds produced in the reaction below (i.e., n = 1 and n = 2) were formed in 38% and 42% yields respectively . 

A solution of the benzoxazepinone 2 (4.2 g, 26 mmol) in CH2C12 (200 mL) was stirred under N2 and trimethyloxonium tetrafluoroborate (4.0 g, 27 mmol) was added. The mixture was stirred for 24 h and then neutralized with coned aq K2C03. The filtered solution was evaporated and the residue distilled in a Kugelrohr apparatus to give the product yield 4.2 g (90%) pale-yellow oil. 

Method A i01 Equivalent amounts of a 1,2,3-benzothiadiazole. sulfur (as S8) and DABCO were added to Decalin (10 mL per gram of benzothiadiazole) and N2 was passed through the mixture. The mixture was heated at 160-190 C until N2 evolution ceased (20-90 min). It was cooled and the Decalin was removed by Kugelrohr distillation at 50 C/0.5 Torr. The residue was twice triturated with CH2C12 and the extracts were combined and filtered from sulfur. Chromatography (silica gel, 1 % EtzO/hcxanc) gave the product. The preparations were carried out on a scale of 0.25-10.0 g benzothiadiazole. 

To a solution of 71.9 g (0.276 mol) of chlorotriisopropoxytitanium in 500 ntL of anhyd toluene are added 77.9 g (0.828 mol) of phenol. From the deep red solution, most of the i-PrOH and the solvent is removed by distillation through a 10-cm Vigretlx column. The residue is distilled in a Kugelrohr at 250 C bath temperature at 0.001 Torr to give an oil which crystallizes upon cooling yield 95.8 g (96%). A 0.26M slock solution in THF can be kept as described above. 

Na2S04. Removal of the solvent, followed by Kugelrohr distillation, affords the /5-trimcthylsilyloxy ketones. Solvolysis in 5 mL of CH3OH with a catalytic amount of hydrochloric acid for 5-10 min at 20 %, neutralization with NaHCO v and workup with C H.Cl, as described in Method A, furnishes the /i-hydroxy ketones which are purified by distillation or crystallization. 

To a solution of 165 mg (0.66 mmol) of 3-[6-(trimcthylsilyl)-4-(Z)-hexenyl]-2-cyclohexenone in 10 mL of toluene is added at 0 C 0.1 mL (1.1 equiv) of ethylaluminum dichloride. The mixture is stirred for 25 min at 0°C and is quenched with 20 mL of ice-water, and extracted twice with 30 mL of diethyl ether. The combined organic layer is washed with 50 mL of sat. aq NaHC()3, 50 mL of NaCI, and dried over MgS04. The solvent is removed under reduced pressure and the crude product is distilled with a Kugelrohr apparatus to give a 3 1 mixture of diaslereomers yield 90.5 mg (77%) dr. (synjartti) 3 1. 

This procedure provides a convenient method for the esterification ol a wide variety of carboxylic acids. The reaction proceeds smoothly with sterically hindered acids6 and with acids which contain various functional groups. Esters are obtained in high purity using Kugelrohr distillation as the sole purification technique. In cases where traces of dichloromethane present no problems, the crude product is usually pure enough to be used directly in subsequent reactions. Methyl and ethyl ethers of phenols may also be prepared by this procedure (see Note 8). 

THF (10 ml) was added to the above solution of TMSLi in HMPA, and the mixture immediately cooled to —78°C. A solution of cyclohex-2-enone 1.5mmol) in THF (1ml) was then added dropwise. After stirring for an additional 5 min, methyl iodide (0.5 ml, excess) was added, and the mixture allowed to warm slowly to 0°C. It was then poured into pentane (50 ml) and washed thoroughly with water (2 x 25 ml). After drying and concentration, the residual oil was distilled to give trans-3-trimethylsilyl-2-methylcyclo-hexanone (97%), b.p. 80°C/1 mmHg (Kugelrohr). 

To a solution of thexyldimethylsilyl chloride (11 mmol) and ImH (15 mmol) in DMF (5 ml) was added the alcohol (11 mmol) at ambient temperature. After being stirred at ambient temperature for 16 h, the mixture was diluted with hexane. The hexane phase was washed with water (2x), and then dried. Concentration followed by distillation (Kugelrohr) gave the silyl ether (86-93%). 

E. l-Amino-2-phenylaziridine (Note 23). If the pentane solution from Step D is removed on a rotary evaporator at room temperature, 7.5-7.7 g. (82-85%) of l-amino-2-phenylaziridine, suitable for preparative use, is obtained. Kugelrohr distillation of this material on a 1-2 g. scale (0.01 mm./60-65° oven temperature) (Note 24) gives a recovery of over 90% (Notes 23 and 25). 

The checkers found that although the chromatographed product was a light yellow oil, it was analytically pure. Kugelrohr distillation was required to obtain a colorless oil. 

Boiling points (bp) correspond to uncorrected air-bath temperatures in the Buchi GKR-50 Kugelrohr. 

The boiling point (bp) corresponds to uncorrected air-bath temperature of a Buchi GKR-50 Kugelrohr. 

The crude product was purified by Kugelrohr distillation (98-103°/0.2 mm) followed by column chromatography (55-mm diameter column, 200 g of silica gel, elution with pentane/EtOAc, 50/1), and another Kugelrohr distillation. 

Kugelrohr distillation ovens manufactured by Biichi Glasaparatefabrik are available from Brinkmann Instruments, Inc., Wcstbury, New York. 

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